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diff --git a/gcc/doc/extend.texi b/gcc/doc/extend.texi new file mode 100644 index 000000000..be1c32cc1 --- /dev/null +++ b/gcc/doc/extend.texi @@ -0,0 +1,14546 @@ +@c Copyright (C) 1988, 1989, 1992, 1993, 1994, 1996, 1998, 1999, 2000, 2001, +@c 2002, 2003, 2004, 2005, 2006, 2007, 2008, 2009, 2010, 2011 +@c Free Software Foundation, Inc. + +@c This is part of the GCC manual. +@c For copying conditions, see the file gcc.texi. + +@node C Extensions +@chapter Extensions to the C Language Family +@cindex extensions, C language +@cindex C language extensions + +@opindex pedantic +GNU C provides several language features not found in ISO standard C@. +(The @option{-pedantic} option directs GCC to print a warning message if +any of these features is used.) To test for the availability of these +features in conditional compilation, check for a predefined macro +@code{__GNUC__}, which is always defined under GCC@. + +These extensions are available in C and Objective-C@. Most of them are +also available in C++. @xref{C++ Extensions,,Extensions to the +C++ Language}, for extensions that apply @emph{only} to C++. + +Some features that are in ISO C99 but not C90 or C++ are also, as +extensions, accepted by GCC in C90 mode and in C++. + +@menu +* Statement Exprs:: Putting statements and declarations inside expressions. +* Local Labels:: Labels local to a block. +* Labels as Values:: Getting pointers to labels, and computed gotos. +* Nested Functions:: As in Algol and Pascal, lexical scoping of functions. +* Constructing Calls:: Dispatching a call to another function. +* Typeof:: @code{typeof}: referring to the type of an expression. +* Conditionals:: Omitting the middle operand of a @samp{?:} expression. +* Long Long:: Double-word integers---@code{long long int}. +* __int128:: 128-bit integers---@code{__int128}. +* Complex:: Data types for complex numbers. +* Floating Types:: Additional Floating Types. +* Half-Precision:: Half-Precision Floating Point. +* Decimal Float:: Decimal Floating Types. +* Hex Floats:: Hexadecimal floating-point constants. +* Fixed-Point:: Fixed-Point Types. +* Named Address Spaces::Named address spaces. +* Zero Length:: Zero-length arrays. +* Variable Length:: Arrays whose length is computed at run time. +* Empty Structures:: Structures with no members. +* Variadic Macros:: Macros with a variable number of arguments. +* Escaped Newlines:: Slightly looser rules for escaped newlines. +* Subscripting:: Any array can be subscripted, even if not an lvalue. +* Pointer Arith:: Arithmetic on @code{void}-pointers and function pointers. +* Initializers:: Non-constant initializers. +* Compound Literals:: Compound literals give structures, unions + or arrays as values. +* Designated Inits:: Labeling elements of initializers. +* Cast to Union:: Casting to union type from any member of the union. +* Case Ranges:: `case 1 ... 9' and such. +* Mixed Declarations:: Mixing declarations and code. +* Function Attributes:: Declaring that functions have no side effects, + or that they can never return. +* Attribute Syntax:: Formal syntax for attributes. +* Function Prototypes:: Prototype declarations and old-style definitions. +* C++ Comments:: C++ comments are recognized. +* Dollar Signs:: Dollar sign is allowed in identifiers. +* Character Escapes:: @samp{\e} stands for the character @key{ESC}. +* Variable Attributes:: Specifying attributes of variables. +* Type Attributes:: Specifying attributes of types. +* Alignment:: Inquiring about the alignment of a type or variable. +* Inline:: Defining inline functions (as fast as macros). +* Volatiles:: What constitutes an access to a volatile object. +* Extended Asm:: Assembler instructions with C expressions as operands. + (With them you can define ``built-in'' functions.) +* Constraints:: Constraints for asm operands +* Asm Labels:: Specifying the assembler name to use for a C symbol. +* Explicit Reg Vars:: Defining variables residing in specified registers. +* Alternate Keywords:: @code{__const__}, @code{__asm__}, etc., for header files. +* Incomplete Enums:: @code{enum foo;}, with details to follow. +* Function Names:: Printable strings which are the name of the current + function. +* Return Address:: Getting the return or frame address of a function. +* Vector Extensions:: Using vector instructions through built-in functions. +* Offsetof:: Special syntax for implementing @code{offsetof}. +* Atomic Builtins:: Built-in functions for atomic memory access. +* Object Size Checking:: Built-in functions for limited buffer overflow + checking. +* Other Builtins:: Other built-in functions. +* Target Builtins:: Built-in functions specific to particular targets. +* Target Format Checks:: Format checks specific to particular targets. +* Pragmas:: Pragmas accepted by GCC. +* Unnamed Fields:: Unnamed struct/union fields within structs/unions. +* Thread-Local:: Per-thread variables. +* Binary constants:: Binary constants using the @samp{0b} prefix. +@end menu + +@node Statement Exprs +@section Statements and Declarations in Expressions +@cindex statements inside expressions +@cindex declarations inside expressions +@cindex expressions containing statements +@cindex macros, statements in expressions + +@c the above section title wrapped and causes an underfull hbox.. i +@c changed it from "within" to "in". --mew 4feb93 +A compound statement enclosed in parentheses may appear as an expression +in GNU C@. This allows you to use loops, switches, and local variables +within an expression. + +Recall that a compound statement is a sequence of statements surrounded +by braces; in this construct, parentheses go around the braces. For +example: + +@smallexample +(@{ int y = foo (); int z; + if (y > 0) z = y; + else z = - y; + z; @}) +@end smallexample + +@noindent +is a valid (though slightly more complex than necessary) expression +for the absolute value of @code{foo ()}. + +The last thing in the compound statement should be an expression +followed by a semicolon; the value of this subexpression serves as the +value of the entire construct. (If you use some other kind of statement +last within the braces, the construct has type @code{void}, and thus +effectively no value.) + +This feature is especially useful in making macro definitions ``safe'' (so +that they evaluate each operand exactly once). For example, the +``maximum'' function is commonly defined as a macro in standard C as +follows: + +@smallexample +#define max(a,b) ((a) > (b) ? (a) : (b)) +@end smallexample + +@noindent +@cindex side effects, macro argument +But this definition computes either @var{a} or @var{b} twice, with bad +results if the operand has side effects. In GNU C, if you know the +type of the operands (here taken as @code{int}), you can define +the macro safely as follows: + +@smallexample +#define maxint(a,b) \ + (@{int _a = (a), _b = (b); _a > _b ? _a : _b; @}) +@end smallexample + +Embedded statements are not allowed in constant expressions, such as +the value of an enumeration constant, the width of a bit-field, or +the initial value of a static variable. + +If you don't know the type of the operand, you can still do this, but you +must use @code{typeof} (@pxref{Typeof}). + +In G++, the result value of a statement expression undergoes array and +function pointer decay, and is returned by value to the enclosing +expression. For instance, if @code{A} is a class, then + +@smallexample + A a; + + (@{a;@}).Foo () +@end smallexample + +@noindent +will construct a temporary @code{A} object to hold the result of the +statement expression, and that will be used to invoke @code{Foo}. +Therefore the @code{this} pointer observed by @code{Foo} will not be the +address of @code{a}. + +Any temporaries created within a statement within a statement expression +will be destroyed at the statement's end. This makes statement +expressions inside macros slightly different from function calls. In +the latter case temporaries introduced during argument evaluation will +be destroyed at the end of the statement that includes the function +call. In the statement expression case they will be destroyed during +the statement expression. For instance, + +@smallexample +#define macro(a) (@{__typeof__(a) b = (a); b + 3; @}) +template<typename T> T function(T a) @{ T b = a; return b + 3; @} + +void foo () +@{ + macro (X ()); + function (X ()); +@} +@end smallexample + +@noindent +will have different places where temporaries are destroyed. For the +@code{macro} case, the temporary @code{X} will be destroyed just after +the initialization of @code{b}. In the @code{function} case that +temporary will be destroyed when the function returns. + +These considerations mean that it is probably a bad idea to use +statement-expressions of this form in header files that are designed to +work with C++. (Note that some versions of the GNU C Library contained +header files using statement-expression that lead to precisely this +bug.) + +Jumping into a statement expression with @code{goto} or using a +@code{switch} statement outside the statement expression with a +@code{case} or @code{default} label inside the statement expression is +not permitted. Jumping into a statement expression with a computed +@code{goto} (@pxref{Labels as Values}) yields undefined behavior. +Jumping out of a statement expression is permitted, but if the +statement expression is part of a larger expression then it is +unspecified which other subexpressions of that expression have been +evaluated except where the language definition requires certain +subexpressions to be evaluated before or after the statement +expression. In any case, as with a function call the evaluation of a +statement expression is not interleaved with the evaluation of other +parts of the containing expression. For example, + +@smallexample + foo (), ((@{ bar1 (); goto a; 0; @}) + bar2 ()), baz(); +@end smallexample + +@noindent +will call @code{foo} and @code{bar1} and will not call @code{baz} but +may or may not call @code{bar2}. If @code{bar2} is called, it will be +called after @code{foo} and before @code{bar1} + +@node Local Labels +@section Locally Declared Labels +@cindex local labels +@cindex macros, local labels + +GCC allows you to declare @dfn{local labels} in any nested block +scope. A local label is just like an ordinary label, but you can +only reference it (with a @code{goto} statement, or by taking its +address) within the block in which it was declared. + +A local label declaration looks like this: + +@smallexample +__label__ @var{label}; +@end smallexample + +@noindent +or + +@smallexample +__label__ @var{label1}, @var{label2}, /* @r{@dots{}} */; +@end smallexample + +Local label declarations must come at the beginning of the block, +before any ordinary declarations or statements. + +The label declaration defines the label @emph{name}, but does not define +the label itself. You must do this in the usual way, with +@code{@var{label}:}, within the statements of the statement expression. + +The local label feature is useful for complex macros. If a macro +contains nested loops, a @code{goto} can be useful for breaking out of +them. However, an ordinary label whose scope is the whole function +cannot be used: if the macro can be expanded several times in one +function, the label will be multiply defined in that function. A +local label avoids this problem. For example: + +@smallexample +#define SEARCH(value, array, target) \ +do @{ \ + __label__ found; \ + typeof (target) _SEARCH_target = (target); \ + typeof (*(array)) *_SEARCH_array = (array); \ + int i, j; \ + int value; \ + for (i = 0; i < max; i++) \ + for (j = 0; j < max; j++) \ + if (_SEARCH_array[i][j] == _SEARCH_target) \ + @{ (value) = i; goto found; @} \ + (value) = -1; \ + found:; \ +@} while (0) +@end smallexample + +This could also be written using a statement-expression: + +@smallexample +#define SEARCH(array, target) \ +(@{ \ + __label__ found; \ + typeof (target) _SEARCH_target = (target); \ + typeof (*(array)) *_SEARCH_array = (array); \ + int i, j; \ + int value; \ + for (i = 0; i < max; i++) \ + for (j = 0; j < max; j++) \ + if (_SEARCH_array[i][j] == _SEARCH_target) \ + @{ value = i; goto found; @} \ + value = -1; \ + found: \ + value; \ +@}) +@end smallexample + +Local label declarations also make the labels they declare visible to +nested functions, if there are any. @xref{Nested Functions}, for details. + +@node Labels as Values +@section Labels as Values +@cindex labels as values +@cindex computed gotos +@cindex goto with computed label +@cindex address of a label + +You can get the address of a label defined in the current function +(or a containing function) with the unary operator @samp{&&}. The +value has type @code{void *}. This value is a constant and can be used +wherever a constant of that type is valid. For example: + +@smallexample +void *ptr; +/* @r{@dots{}} */ +ptr = &&foo; +@end smallexample + +To use these values, you need to be able to jump to one. This is done +with the computed goto statement@footnote{The analogous feature in +Fortran is called an assigned goto, but that name seems inappropriate in +C, where one can do more than simply store label addresses in label +variables.}, @code{goto *@var{exp};}. For example, + +@smallexample +goto *ptr; +@end smallexample + +@noindent +Any expression of type @code{void *} is allowed. + +One way of using these constants is in initializing a static array that +will serve as a jump table: + +@smallexample +static void *array[] = @{ &&foo, &&bar, &&hack @}; +@end smallexample + +Then you can select a label with indexing, like this: + +@smallexample +goto *array[i]; +@end smallexample + +@noindent +Note that this does not check whether the subscript is in bounds---array +indexing in C never does that. + +Such an array of label values serves a purpose much like that of the +@code{switch} statement. The @code{switch} statement is cleaner, so +use that rather than an array unless the problem does not fit a +@code{switch} statement very well. + +Another use of label values is in an interpreter for threaded code. +The labels within the interpreter function can be stored in the +threaded code for super-fast dispatching. + +You may not use this mechanism to jump to code in a different function. +If you do that, totally unpredictable things will happen. The best way to +avoid this is to store the label address only in automatic variables and +never pass it as an argument. + +An alternate way to write the above example is + +@smallexample +static const int array[] = @{ &&foo - &&foo, &&bar - &&foo, + &&hack - &&foo @}; +goto *(&&foo + array[i]); +@end smallexample + +@noindent +This is more friendly to code living in shared libraries, as it reduces +the number of dynamic relocations that are needed, and by consequence, +allows the data to be read-only. + +The @code{&&foo} expressions for the same label might have different +values if the containing function is inlined or cloned. If a program +relies on them being always the same, +@code{__attribute__((__noinline__,__noclone__))} should be used to +prevent inlining and cloning. If @code{&&foo} is used in a static +variable initializer, inlining and cloning is forbidden. + +@node Nested Functions +@section Nested Functions +@cindex nested functions +@cindex downward funargs +@cindex thunks + +A @dfn{nested function} is a function defined inside another function. +(Nested functions are not supported for GNU C++.) The nested function's +name is local to the block where it is defined. For example, here we +define a nested function named @code{square}, and call it twice: + +@smallexample +@group +foo (double a, double b) +@{ + double square (double z) @{ return z * z; @} + + return square (a) + square (b); +@} +@end group +@end smallexample + +The nested function can access all the variables of the containing +function that are visible at the point of its definition. This is +called @dfn{lexical scoping}. For example, here we show a nested +function which uses an inherited variable named @code{offset}: + +@smallexample +@group +bar (int *array, int offset, int size) +@{ + int access (int *array, int index) + @{ return array[index + offset]; @} + int i; + /* @r{@dots{}} */ + for (i = 0; i < size; i++) + /* @r{@dots{}} */ access (array, i) /* @r{@dots{}} */ +@} +@end group +@end smallexample + +Nested function definitions are permitted within functions in the places +where variable definitions are allowed; that is, in any block, mixed +with the other declarations and statements in the block. + +It is possible to call the nested function from outside the scope of its +name by storing its address or passing the address to another function: + +@smallexample +hack (int *array, int size) +@{ + void store (int index, int value) + @{ array[index] = value; @} + + intermediate (store, size); +@} +@end smallexample + +Here, the function @code{intermediate} receives the address of +@code{store} as an argument. If @code{intermediate} calls @code{store}, +the arguments given to @code{store} are used to store into @code{array}. +But this technique works only so long as the containing function +(@code{hack}, in this example) does not exit. + +If you try to call the nested function through its address after the +containing function has exited, all hell will break loose. If you try +to call it after a containing scope level has exited, and if it refers +to some of the variables that are no longer in scope, you may be lucky, +but it's not wise to take the risk. If, however, the nested function +does not refer to anything that has gone out of scope, you should be +safe. + +GCC implements taking the address of a nested function using a technique +called @dfn{trampolines}. This technique was described in +@cite{Lexical Closures for C++} (Thomas M. Breuel, USENIX +C++ Conference Proceedings, October 17-21, 1988). + +A nested function can jump to a label inherited from a containing +function, provided the label was explicitly declared in the containing +function (@pxref{Local Labels}). Such a jump returns instantly to the +containing function, exiting the nested function which did the +@code{goto} and any intermediate functions as well. Here is an example: + +@smallexample +@group +bar (int *array, int offset, int size) +@{ + __label__ failure; + int access (int *array, int index) + @{ + if (index > size) + goto failure; + return array[index + offset]; + @} + int i; + /* @r{@dots{}} */ + for (i = 0; i < size; i++) + /* @r{@dots{}} */ access (array, i) /* @r{@dots{}} */ + /* @r{@dots{}} */ + return 0; + + /* @r{Control comes here from @code{access} + if it detects an error.} */ + failure: + return -1; +@} +@end group +@end smallexample + +A nested function always has no linkage. Declaring one with +@code{extern} or @code{static} is erroneous. If you need to declare the nested function +before its definition, use @code{auto} (which is otherwise meaningless +for function declarations). + +@smallexample +bar (int *array, int offset, int size) +@{ + __label__ failure; + auto int access (int *, int); + /* @r{@dots{}} */ + int access (int *array, int index) + @{ + if (index > size) + goto failure; + return array[index + offset]; + @} + /* @r{@dots{}} */ +@} +@end smallexample + +@node Constructing Calls +@section Constructing Function Calls +@cindex constructing calls +@cindex forwarding calls + +Using the built-in functions described below, you can record +the arguments a function received, and call another function +with the same arguments, without knowing the number or types +of the arguments. + +You can also record the return value of that function call, +and later return that value, without knowing what data type +the function tried to return (as long as your caller expects +that data type). + +However, these built-in functions may interact badly with some +sophisticated features or other extensions of the language. It +is, therefore, not recommended to use them outside very simple +functions acting as mere forwarders for their arguments. + +@deftypefn {Built-in Function} {void *} __builtin_apply_args () +This built-in function returns a pointer to data +describing how to perform a call with the same arguments as were passed +to the current function. + +The function saves the arg pointer register, structure value address, +and all registers that might be used to pass arguments to a function +into a block of memory allocated on the stack. Then it returns the +address of that block. +@end deftypefn + +@deftypefn {Built-in Function} {void *} __builtin_apply (void (*@var{function})(), void *@var{arguments}, size_t @var{size}) +This built-in function invokes @var{function} +with a copy of the parameters described by @var{arguments} +and @var{size}. + +The value of @var{arguments} should be the value returned by +@code{__builtin_apply_args}. The argument @var{size} specifies the size +of the stack argument data, in bytes. + +This function returns a pointer to data describing +how to return whatever value was returned by @var{function}. The data +is saved in a block of memory allocated on the stack. + +It is not always simple to compute the proper value for @var{size}. The +value is used by @code{__builtin_apply} to compute the amount of data +that should be pushed on the stack and copied from the incoming argument +area. +@end deftypefn + +@deftypefn {Built-in Function} {void} __builtin_return (void *@var{result}) +This built-in function returns the value described by @var{result} from +the containing function. You should specify, for @var{result}, a value +returned by @code{__builtin_apply}. +@end deftypefn + +@deftypefn {Built-in Function} {} __builtin_va_arg_pack () +This built-in function represents all anonymous arguments of an inline +function. It can be used only in inline functions which will be always +inlined, never compiled as a separate function, such as those using +@code{__attribute__ ((__always_inline__))} or +@code{__attribute__ ((__gnu_inline__))} extern inline functions. +It must be only passed as last argument to some other function +with variable arguments. This is useful for writing small wrapper +inlines for variable argument functions, when using preprocessor +macros is undesirable. For example: +@smallexample +extern int myprintf (FILE *f, const char *format, ...); +extern inline __attribute__ ((__gnu_inline__)) int +myprintf (FILE *f, const char *format, ...) +@{ + int r = fprintf (f, "myprintf: "); + if (r < 0) + return r; + int s = fprintf (f, format, __builtin_va_arg_pack ()); + if (s < 0) + return s; + return r + s; +@} +@end smallexample +@end deftypefn + +@deftypefn {Built-in Function} {size_t} __builtin_va_arg_pack_len () +This built-in function returns the number of anonymous arguments of +an inline function. It can be used only in inline functions which +will be always inlined, never compiled as a separate function, such +as those using @code{__attribute__ ((__always_inline__))} or +@code{__attribute__ ((__gnu_inline__))} extern inline functions. +For example following will do link or runtime checking of open +arguments for optimized code: +@smallexample +#ifdef __OPTIMIZE__ +extern inline __attribute__((__gnu_inline__)) int +myopen (const char *path, int oflag, ...) +@{ + if (__builtin_va_arg_pack_len () > 1) + warn_open_too_many_arguments (); + + if (__builtin_constant_p (oflag)) + @{ + if ((oflag & O_CREAT) != 0 && __builtin_va_arg_pack_len () < 1) + @{ + warn_open_missing_mode (); + return __open_2 (path, oflag); + @} + return open (path, oflag, __builtin_va_arg_pack ()); + @} + + if (__builtin_va_arg_pack_len () < 1) + return __open_2 (path, oflag); + + return open (path, oflag, __builtin_va_arg_pack ()); +@} +#endif +@end smallexample +@end deftypefn + +@node Typeof +@section Referring to a Type with @code{typeof} +@findex typeof +@findex sizeof +@cindex macros, types of arguments + +Another way to refer to the type of an expression is with @code{typeof}. +The syntax of using of this keyword looks like @code{sizeof}, but the +construct acts semantically like a type name defined with @code{typedef}. + +There are two ways of writing the argument to @code{typeof}: with an +expression or with a type. Here is an example with an expression: + +@smallexample +typeof (x[0](1)) +@end smallexample + +@noindent +This assumes that @code{x} is an array of pointers to functions; +the type described is that of the values of the functions. + +Here is an example with a typename as the argument: + +@smallexample +typeof (int *) +@end smallexample + +@noindent +Here the type described is that of pointers to @code{int}. + +If you are writing a header file that must work when included in ISO C +programs, write @code{__typeof__} instead of @code{typeof}. +@xref{Alternate Keywords}. + +A @code{typeof}-construct can be used anywhere a typedef name could be +used. For example, you can use it in a declaration, in a cast, or inside +of @code{sizeof} or @code{typeof}. + +The operand of @code{typeof} is evaluated for its side effects if and +only if it is an expression of variably modified type or the name of +such a type. + +@code{typeof} is often useful in conjunction with the +statements-within-expressions feature. Here is how the two together can +be used to define a safe ``maximum'' macro that operates on any +arithmetic type and evaluates each of its arguments exactly once: + +@smallexample +#define max(a,b) \ + (@{ typeof (a) _a = (a); \ + typeof (b) _b = (b); \ + _a > _b ? _a : _b; @}) +@end smallexample + +@cindex underscores in variables in macros +@cindex @samp{_} in variables in macros +@cindex local variables in macros +@cindex variables, local, in macros +@cindex macros, local variables in + +The reason for using names that start with underscores for the local +variables is to avoid conflicts with variable names that occur within the +expressions that are substituted for @code{a} and @code{b}. Eventually we +hope to design a new form of declaration syntax that allows you to declare +variables whose scopes start only after their initializers; this will be a +more reliable way to prevent such conflicts. + +@noindent +Some more examples of the use of @code{typeof}: + +@itemize @bullet +@item +This declares @code{y} with the type of what @code{x} points to. + +@smallexample +typeof (*x) y; +@end smallexample + +@item +This declares @code{y} as an array of such values. + +@smallexample +typeof (*x) y[4]; +@end smallexample + +@item +This declares @code{y} as an array of pointers to characters: + +@smallexample +typeof (typeof (char *)[4]) y; +@end smallexample + +@noindent +It is equivalent to the following traditional C declaration: + +@smallexample +char *y[4]; +@end smallexample + +To see the meaning of the declaration using @code{typeof}, and why it +might be a useful way to write, rewrite it with these macros: + +@smallexample +#define pointer(T) typeof(T *) +#define array(T, N) typeof(T [N]) +@end smallexample + +@noindent +Now the declaration can be rewritten this way: + +@smallexample +array (pointer (char), 4) y; +@end smallexample + +@noindent +Thus, @code{array (pointer (char), 4)} is the type of arrays of 4 +pointers to @code{char}. +@end itemize + +@emph{Compatibility Note:} In addition to @code{typeof}, GCC 2 supported +a more limited extension which permitted one to write + +@smallexample +typedef @var{T} = @var{expr}; +@end smallexample + +@noindent +with the effect of declaring @var{T} to have the type of the expression +@var{expr}. This extension does not work with GCC 3 (versions between +3.0 and 3.2 will crash; 3.2.1 and later give an error). Code which +relies on it should be rewritten to use @code{typeof}: + +@smallexample +typedef typeof(@var{expr}) @var{T}; +@end smallexample + +@noindent +This will work with all versions of GCC@. + +@node Conditionals +@section Conditionals with Omitted Operands +@cindex conditional expressions, extensions +@cindex omitted middle-operands +@cindex middle-operands, omitted +@cindex extensions, @code{?:} +@cindex @code{?:} extensions + +The middle operand in a conditional expression may be omitted. Then +if the first operand is nonzero, its value is the value of the conditional +expression. + +Therefore, the expression + +@smallexample +x ? : y +@end smallexample + +@noindent +has the value of @code{x} if that is nonzero; otherwise, the value of +@code{y}. + +This example is perfectly equivalent to + +@smallexample +x ? x : y +@end smallexample + +@cindex side effect in @code{?:} +@cindex @code{?:} side effect +@noindent +In this simple case, the ability to omit the middle operand is not +especially useful. When it becomes useful is when the first operand does, +or may (if it is a macro argument), contain a side effect. Then repeating +the operand in the middle would perform the side effect twice. Omitting +the middle operand uses the value already computed without the undesirable +effects of recomputing it. + +@node __int128 +@section 128-bits integers +@cindex @code{__int128} data types + +As an extension the integer scalar type @code{__int128} is supported for +targets having an integer mode wide enough to hold 128-bit. +Simply write @code{__int128} for a signed 128-bit integer, or +@code{unsigned __int128} for an unsigned 128-bit integer. There is no +support in GCC to express an integer constant of type @code{__int128} +for targets having @code{long long} integer with less then 128 bit width. + +@node Long Long +@section Double-Word Integers +@cindex @code{long long} data types +@cindex double-word arithmetic +@cindex multiprecision arithmetic +@cindex @code{LL} integer suffix +@cindex @code{ULL} integer suffix + +ISO C99 supports data types for integers that are at least 64 bits wide, +and as an extension GCC supports them in C90 mode and in C++. +Simply write @code{long long int} for a signed integer, or +@code{unsigned long long int} for an unsigned integer. To make an +integer constant of type @code{long long int}, add the suffix @samp{LL} +to the integer. To make an integer constant of type @code{unsigned long +long int}, add the suffix @samp{ULL} to the integer. + +You can use these types in arithmetic like any other integer types. +Addition, subtraction, and bitwise boolean operations on these types +are open-coded on all types of machines. Multiplication is open-coded +if the machine supports fullword-to-doubleword a widening multiply +instruction. Division and shifts are open-coded only on machines that +provide special support. The operations that are not open-coded use +special library routines that come with GCC@. + +There may be pitfalls when you use @code{long long} types for function +arguments, unless you declare function prototypes. If a function +expects type @code{int} for its argument, and you pass a value of type +@code{long long int}, confusion will result because the caller and the +subroutine will disagree about the number of bytes for the argument. +Likewise, if the function expects @code{long long int} and you pass +@code{int}. The best way to avoid such problems is to use prototypes. + +@node Complex +@section Complex Numbers +@cindex complex numbers +@cindex @code{_Complex} keyword +@cindex @code{__complex__} keyword + +ISO C99 supports complex floating data types, and as an extension GCC +supports them in C90 mode and in C++, and supports complex integer data +types which are not part of ISO C99. You can declare complex types +using the keyword @code{_Complex}. As an extension, the older GNU +keyword @code{__complex__} is also supported. + +For example, @samp{_Complex double x;} declares @code{x} as a +variable whose real part and imaginary part are both of type +@code{double}. @samp{_Complex short int y;} declares @code{y} to +have real and imaginary parts of type @code{short int}; this is not +likely to be useful, but it shows that the set of complex types is +complete. + +To write a constant with a complex data type, use the suffix @samp{i} or +@samp{j} (either one; they are equivalent). For example, @code{2.5fi} +has type @code{_Complex float} and @code{3i} has type +@code{_Complex int}. Such a constant always has a pure imaginary +value, but you can form any complex value you like by adding one to a +real constant. This is a GNU extension; if you have an ISO C99 +conforming C library (such as GNU libc), and want to construct complex +constants of floating type, you should include @code{<complex.h>} and +use the macros @code{I} or @code{_Complex_I} instead. + +@cindex @code{__real__} keyword +@cindex @code{__imag__} keyword +To extract the real part of a complex-valued expression @var{exp}, write +@code{__real__ @var{exp}}. Likewise, use @code{__imag__} to +extract the imaginary part. This is a GNU extension; for values of +floating type, you should use the ISO C99 functions @code{crealf}, +@code{creal}, @code{creall}, @code{cimagf}, @code{cimag} and +@code{cimagl}, declared in @code{<complex.h>} and also provided as +built-in functions by GCC@. + +@cindex complex conjugation +The operator @samp{~} performs complex conjugation when used on a value +with a complex type. This is a GNU extension; for values of +floating type, you should use the ISO C99 functions @code{conjf}, +@code{conj} and @code{conjl}, declared in @code{<complex.h>} and also +provided as built-in functions by GCC@. + +GCC can allocate complex automatic variables in a noncontiguous +fashion; it's even possible for the real part to be in a register while +the imaginary part is on the stack (or vice-versa). Only the DWARF2 +debug info format can represent this, so use of DWARF2 is recommended. +If you are using the stabs debug info format, GCC describes a noncontiguous +complex variable as if it were two separate variables of noncomplex type. +If the variable's actual name is @code{foo}, the two fictitious +variables are named @code{foo$real} and @code{foo$imag}. You can +examine and set these two fictitious variables with your debugger. + +@node Floating Types +@section Additional Floating Types +@cindex additional floating types +@cindex @code{__float80} data type +@cindex @code{__float128} data type +@cindex @code{w} floating point suffix +@cindex @code{q} floating point suffix +@cindex @code{W} floating point suffix +@cindex @code{Q} floating point suffix + +As an extension, the GNU C compiler supports additional floating +types, @code{__float80} and @code{__float128} to support 80bit +(@code{XFmode}) and 128 bit (@code{TFmode}) floating types. +Support for additional types includes the arithmetic operators: +add, subtract, multiply, divide; unary arithmetic operators; +relational operators; equality operators; and conversions to and from +integer and other floating types. Use a suffix @samp{w} or @samp{W} +in a literal constant of type @code{__float80} and @samp{q} or @samp{Q} +for @code{_float128}. You can declare complex types using the +corresponding internal complex type, @code{XCmode} for @code{__float80} +type and @code{TCmode} for @code{__float128} type: + +@smallexample +typedef _Complex float __attribute__((mode(TC))) _Complex128; +typedef _Complex float __attribute__((mode(XC))) _Complex80; +@end smallexample + +Not all targets support additional floating point types. @code{__float80} +and @code{__float128} types are supported on i386, x86_64 and ia64 targets. +The @code{__float128} type is supported on hppa HP-UX targets. + +@node Half-Precision +@section Half-Precision Floating Point +@cindex half-precision floating point +@cindex @code{__fp16} data type + +On ARM targets, GCC supports half-precision (16-bit) floating point via +the @code{__fp16} type. You must enable this type explicitly +with the @option{-mfp16-format} command-line option in order to use it. + +ARM supports two incompatible representations for half-precision +floating-point values. You must choose one of the representations and +use it consistently in your program. + +Specifying @option{-mfp16-format=ieee} selects the IEEE 754-2008 format. +This format can represent normalized values in the range of @math{2^{-14}} to 65504. +There are 11 bits of significand precision, approximately 3 +decimal digits. + +Specifying @option{-mfp16-format=alternative} selects the ARM +alternative format. This representation is similar to the IEEE +format, but does not support infinities or NaNs. Instead, the range +of exponents is extended, so that this format can represent normalized +values in the range of @math{2^{-14}} to 131008. + +The @code{__fp16} type is a storage format only. For purposes +of arithmetic and other operations, @code{__fp16} values in C or C++ +expressions are automatically promoted to @code{float}. In addition, +you cannot declare a function with a return value or parameters +of type @code{__fp16}. + +Note that conversions from @code{double} to @code{__fp16} +involve an intermediate conversion to @code{float}. Because +of rounding, this can sometimes produce a different result than a +direct conversion. + +ARM provides hardware support for conversions between +@code{__fp16} and @code{float} values +as an extension to VFP and NEON (Advanced SIMD). GCC generates +code using these hardware instructions if you compile with +options to select an FPU that provides them; +for example, @option{-mfpu=neon-fp16 -mfloat-abi=softfp}, +in addition to the @option{-mfp16-format} option to select +a half-precision format. + +Language-level support for the @code{__fp16} data type is +independent of whether GCC generates code using hardware floating-point +instructions. In cases where hardware support is not specified, GCC +implements conversions between @code{__fp16} and @code{float} values +as library calls. + +@node Decimal Float +@section Decimal Floating Types +@cindex decimal floating types +@cindex @code{_Decimal32} data type +@cindex @code{_Decimal64} data type +@cindex @code{_Decimal128} data type +@cindex @code{df} integer suffix +@cindex @code{dd} integer suffix +@cindex @code{dl} integer suffix +@cindex @code{DF} integer suffix +@cindex @code{DD} integer suffix +@cindex @code{DL} integer suffix + +As an extension, the GNU C compiler supports decimal floating types as +defined in the N1312 draft of ISO/IEC WDTR24732. Support for decimal +floating types in GCC will evolve as the draft technical report changes. +Calling conventions for any target might also change. Not all targets +support decimal floating types. + +The decimal floating types are @code{_Decimal32}, @code{_Decimal64}, and +@code{_Decimal128}. They use a radix of ten, unlike the floating types +@code{float}, @code{double}, and @code{long double} whose radix is not +specified by the C standard but is usually two. + +Support for decimal floating types includes the arithmetic operators +add, subtract, multiply, divide; unary arithmetic operators; +relational operators; equality operators; and conversions to and from +integer and other floating types. Use a suffix @samp{df} or +@samp{DF} in a literal constant of type @code{_Decimal32}, @samp{dd} +or @samp{DD} for @code{_Decimal64}, and @samp{dl} or @samp{DL} for +@code{_Decimal128}. + +GCC support of decimal float as specified by the draft technical report +is incomplete: + +@itemize @bullet +@item +When the value of a decimal floating type cannot be represented in the +integer type to which it is being converted, the result is undefined +rather than the result value specified by the draft technical report. + +@item +GCC does not provide the C library functionality associated with +@file{math.h}, @file{fenv.h}, @file{stdio.h}, @file{stdlib.h}, and +@file{wchar.h}, which must come from a separate C library implementation. +Because of this the GNU C compiler does not define macro +@code{__STDC_DEC_FP__} to indicate that the implementation conforms to +the technical report. +@end itemize + +Types @code{_Decimal32}, @code{_Decimal64}, and @code{_Decimal128} +are supported by the DWARF2 debug information format. + +@node Hex Floats +@section Hex Floats +@cindex hex floats + +ISO C99 supports floating-point numbers written not only in the usual +decimal notation, such as @code{1.55e1}, but also numbers such as +@code{0x1.fp3} written in hexadecimal format. As a GNU extension, GCC +supports this in C90 mode (except in some cases when strictly +conforming) and in C++. In that format the +@samp{0x} hex introducer and the @samp{p} or @samp{P} exponent field are +mandatory. The exponent is a decimal number that indicates the power of +2 by which the significant part will be multiplied. Thus @samp{0x1.f} is +@tex +$1 {15\over16}$, +@end tex +@ifnottex +1 15/16, +@end ifnottex +@samp{p3} multiplies it by 8, and the value of @code{0x1.fp3} +is the same as @code{1.55e1}. + +Unlike for floating-point numbers in the decimal notation the exponent +is always required in the hexadecimal notation. Otherwise the compiler +would not be able to resolve the ambiguity of, e.g., @code{0x1.f}. This +could mean @code{1.0f} or @code{1.9375} since @samp{f} is also the +extension for floating-point constants of type @code{float}. + +@node Fixed-Point +@section Fixed-Point Types +@cindex fixed-point types +@cindex @code{_Fract} data type +@cindex @code{_Accum} data type +@cindex @code{_Sat} data type +@cindex @code{hr} fixed-suffix +@cindex @code{r} fixed-suffix +@cindex @code{lr} fixed-suffix +@cindex @code{llr} fixed-suffix +@cindex @code{uhr} fixed-suffix +@cindex @code{ur} fixed-suffix +@cindex @code{ulr} fixed-suffix +@cindex @code{ullr} fixed-suffix +@cindex @code{hk} fixed-suffix +@cindex @code{k} fixed-suffix +@cindex @code{lk} fixed-suffix +@cindex @code{llk} fixed-suffix +@cindex @code{uhk} fixed-suffix +@cindex @code{uk} fixed-suffix +@cindex @code{ulk} fixed-suffix +@cindex @code{ullk} fixed-suffix +@cindex @code{HR} fixed-suffix +@cindex @code{R} fixed-suffix +@cindex @code{LR} fixed-suffix +@cindex @code{LLR} fixed-suffix +@cindex @code{UHR} fixed-suffix +@cindex @code{UR} fixed-suffix +@cindex @code{ULR} fixed-suffix +@cindex @code{ULLR} fixed-suffix +@cindex @code{HK} fixed-suffix +@cindex @code{K} fixed-suffix +@cindex @code{LK} fixed-suffix +@cindex @code{LLK} fixed-suffix +@cindex @code{UHK} fixed-suffix +@cindex @code{UK} fixed-suffix +@cindex @code{ULK} fixed-suffix +@cindex @code{ULLK} fixed-suffix + +As an extension, the GNU C compiler supports fixed-point types as +defined in the N1169 draft of ISO/IEC DTR 18037. Support for fixed-point +types in GCC will evolve as the draft technical report changes. +Calling conventions for any target might also change. Not all targets +support fixed-point types. + +The fixed-point types are +@code{short _Fract}, +@code{_Fract}, +@code{long _Fract}, +@code{long long _Fract}, +@code{unsigned short _Fract}, +@code{unsigned _Fract}, +@code{unsigned long _Fract}, +@code{unsigned long long _Fract}, +@code{_Sat short _Fract}, +@code{_Sat _Fract}, +@code{_Sat long _Fract}, +@code{_Sat long long _Fract}, +@code{_Sat unsigned short _Fract}, +@code{_Sat unsigned _Fract}, +@code{_Sat unsigned long _Fract}, +@code{_Sat unsigned long long _Fract}, +@code{short _Accum}, +@code{_Accum}, +@code{long _Accum}, +@code{long long _Accum}, +@code{unsigned short _Accum}, +@code{unsigned _Accum}, +@code{unsigned long _Accum}, +@code{unsigned long long _Accum}, +@code{_Sat short _Accum}, +@code{_Sat _Accum}, +@code{_Sat long _Accum}, +@code{_Sat long long _Accum}, +@code{_Sat unsigned short _Accum}, +@code{_Sat unsigned _Accum}, +@code{_Sat unsigned long _Accum}, +@code{_Sat unsigned long long _Accum}. + +Fixed-point data values contain fractional and optional integral parts. +The format of fixed-point data varies and depends on the target machine. + +Support for fixed-point types includes: +@itemize @bullet +@item +prefix and postfix increment and decrement operators (@code{++}, @code{--}) +@item +unary arithmetic operators (@code{+}, @code{-}, @code{!}) +@item +binary arithmetic operators (@code{+}, @code{-}, @code{*}, @code{/}) +@item +binary shift operators (@code{<<}, @code{>>}) +@item +relational operators (@code{<}, @code{<=}, @code{>=}, @code{>}) +@item +equality operators (@code{==}, @code{!=}) +@item +assignment operators (@code{+=}, @code{-=}, @code{*=}, @code{/=}, +@code{<<=}, @code{>>=}) +@item +conversions to and from integer, floating-point, or fixed-point types +@end itemize + +Use a suffix in a fixed-point literal constant: +@itemize +@item @samp{hr} or @samp{HR} for @code{short _Fract} and +@code{_Sat short _Fract} +@item @samp{r} or @samp{R} for @code{_Fract} and @code{_Sat _Fract} +@item @samp{lr} or @samp{LR} for @code{long _Fract} and +@code{_Sat long _Fract} +@item @samp{llr} or @samp{LLR} for @code{long long _Fract} and +@code{_Sat long long _Fract} +@item @samp{uhr} or @samp{UHR} for @code{unsigned short _Fract} and +@code{_Sat unsigned short _Fract} +@item @samp{ur} or @samp{UR} for @code{unsigned _Fract} and +@code{_Sat unsigned _Fract} +@item @samp{ulr} or @samp{ULR} for @code{unsigned long _Fract} and +@code{_Sat unsigned long _Fract} +@item @samp{ullr} or @samp{ULLR} for @code{unsigned long long _Fract} +and @code{_Sat unsigned long long _Fract} +@item @samp{hk} or @samp{HK} for @code{short _Accum} and +@code{_Sat short _Accum} +@item @samp{k} or @samp{K} for @code{_Accum} and @code{_Sat _Accum} +@item @samp{lk} or @samp{LK} for @code{long _Accum} and +@code{_Sat long _Accum} +@item @samp{llk} or @samp{LLK} for @code{long long _Accum} and +@code{_Sat long long _Accum} +@item @samp{uhk} or @samp{UHK} for @code{unsigned short _Accum} and +@code{_Sat unsigned short _Accum} +@item @samp{uk} or @samp{UK} for @code{unsigned _Accum} and +@code{_Sat unsigned _Accum} +@item @samp{ulk} or @samp{ULK} for @code{unsigned long _Accum} and +@code{_Sat unsigned long _Accum} +@item @samp{ullk} or @samp{ULLK} for @code{unsigned long long _Accum} +and @code{_Sat unsigned long long _Accum} +@end itemize + +GCC support of fixed-point types as specified by the draft technical report +is incomplete: + +@itemize @bullet +@item +Pragmas to control overflow and rounding behaviors are not implemented. +@end itemize + +Fixed-point types are supported by the DWARF2 debug information format. + +@node Named Address Spaces +@section Named address spaces +@cindex named address spaces + +As an extension, the GNU C compiler supports named address spaces as +defined in the N1275 draft of ISO/IEC DTR 18037. Support for named +address spaces in GCC will evolve as the draft technical report changes. +Calling conventions for any target might also change. At present, only +the SPU and M32C targets support other address spaces. On the SPU target, for +example, variables may be declared as belonging to another address space +by qualifying the type with the @code{__ea} address space identifier: + +@smallexample +extern int __ea i; +@end smallexample + +When the variable @code{i} is accessed, the compiler will generate +special code to access this variable. It may use runtime library +support, or generate special machine instructions to access that address +space. + +The @code{__ea} identifier may be used exactly like any other C type +qualifier (e.g., @code{const} or @code{volatile}). See the N1275 +document for more details. + +On the M32C target, with the R8C and M16C cpu variants, variables +qualified with @code{__far} are accessed using 32-bit addresses in +order to access memory beyond the first 64k bytes. If @code{__far} is +used with the M32CM or M32C cpu variants, it has no effect. + +@node Zero Length +@section Arrays of Length Zero +@cindex arrays of length zero +@cindex zero-length arrays +@cindex length-zero arrays +@cindex flexible array members + +Zero-length arrays are allowed in GNU C@. They are very useful as the +last element of a structure which is really a header for a variable-length +object: + +@smallexample +struct line @{ + int length; + char contents[0]; +@}; + +struct line *thisline = (struct line *) + malloc (sizeof (struct line) + this_length); +thisline->length = this_length; +@end smallexample + +In ISO C90, you would have to give @code{contents} a length of 1, which +means either you waste space or complicate the argument to @code{malloc}. + +In ISO C99, you would use a @dfn{flexible array member}, which is +slightly different in syntax and semantics: + +@itemize @bullet +@item +Flexible array members are written as @code{contents[]} without +the @code{0}. + +@item +Flexible array members have incomplete type, and so the @code{sizeof} +operator may not be applied. As a quirk of the original implementation +of zero-length arrays, @code{sizeof} evaluates to zero. + +@item +Flexible array members may only appear as the last member of a +@code{struct} that is otherwise non-empty. + +@item +A structure containing a flexible array member, or a union containing +such a structure (possibly recursively), may not be a member of a +structure or an element of an array. (However, these uses are +permitted by GCC as extensions.) +@end itemize + +GCC versions before 3.0 allowed zero-length arrays to be statically +initialized, as if they were flexible arrays. In addition to those +cases that were useful, it also allowed initializations in situations +that would corrupt later data. Non-empty initialization of zero-length +arrays is now treated like any case where there are more initializer +elements than the array holds, in that a suitable warning about "excess +elements in array" is given, and the excess elements (all of them, in +this case) are ignored. + +Instead GCC allows static initialization of flexible array members. +This is equivalent to defining a new structure containing the original +structure followed by an array of sufficient size to contain the data. +I.e.@: in the following, @code{f1} is constructed as if it were declared +like @code{f2}. + +@smallexample +struct f1 @{ + int x; int y[]; +@} f1 = @{ 1, @{ 2, 3, 4 @} @}; + +struct f2 @{ + struct f1 f1; int data[3]; +@} f2 = @{ @{ 1 @}, @{ 2, 3, 4 @} @}; +@end smallexample + +@noindent +The convenience of this extension is that @code{f1} has the desired +type, eliminating the need to consistently refer to @code{f2.f1}. + +This has symmetry with normal static arrays, in that an array of +unknown size is also written with @code{[]}. + +Of course, this extension only makes sense if the extra data comes at +the end of a top-level object, as otherwise we would be overwriting +data at subsequent offsets. To avoid undue complication and confusion +with initialization of deeply nested arrays, we simply disallow any +non-empty initialization except when the structure is the top-level +object. For example: + +@smallexample +struct foo @{ int x; int y[]; @}; +struct bar @{ struct foo z; @}; + +struct foo a = @{ 1, @{ 2, 3, 4 @} @}; // @r{Valid.} +struct bar b = @{ @{ 1, @{ 2, 3, 4 @} @} @}; // @r{Invalid.} +struct bar c = @{ @{ 1, @{ @} @} @}; // @r{Valid.} +struct foo d[1] = @{ @{ 1 @{ 2, 3, 4 @} @} @}; // @r{Invalid.} +@end smallexample + +@node Empty Structures +@section Structures With No Members +@cindex empty structures +@cindex zero-size structures + +GCC permits a C structure to have no members: + +@smallexample +struct empty @{ +@}; +@end smallexample + +The structure will have size zero. In C++, empty structures are part +of the language. G++ treats empty structures as if they had a single +member of type @code{char}. + +@node Variable Length +@section Arrays of Variable Length +@cindex variable-length arrays +@cindex arrays of variable length +@cindex VLAs + +Variable-length automatic arrays are allowed in ISO C99, and as an +extension GCC accepts them in C90 mode and in C++. These arrays are +declared like any other automatic arrays, but with a length that is not +a constant expression. The storage is allocated at the point of +declaration and deallocated when the brace-level is exited. For +example: + +@smallexample +FILE * +concat_fopen (char *s1, char *s2, char *mode) +@{ + char str[strlen (s1) + strlen (s2) + 1]; + strcpy (str, s1); + strcat (str, s2); + return fopen (str, mode); +@} +@end smallexample + +@cindex scope of a variable length array +@cindex variable-length array scope +@cindex deallocating variable length arrays +Jumping or breaking out of the scope of the array name deallocates the +storage. Jumping into the scope is not allowed; you get an error +message for it. + +@cindex @code{alloca} vs variable-length arrays +You can use the function @code{alloca} to get an effect much like +variable-length arrays. The function @code{alloca} is available in +many other C implementations (but not in all). On the other hand, +variable-length arrays are more elegant. + +There are other differences between these two methods. Space allocated +with @code{alloca} exists until the containing @emph{function} returns. +The space for a variable-length array is deallocated as soon as the array +name's scope ends. (If you use both variable-length arrays and +@code{alloca} in the same function, deallocation of a variable-length array +will also deallocate anything more recently allocated with @code{alloca}.) + +You can also use variable-length arrays as arguments to functions: + +@smallexample +struct entry +tester (int len, char data[len][len]) +@{ + /* @r{@dots{}} */ +@} +@end smallexample + +The length of an array is computed once when the storage is allocated +and is remembered for the scope of the array in case you access it with +@code{sizeof}. + +If you want to pass the array first and the length afterward, you can +use a forward declaration in the parameter list---another GNU extension. + +@smallexample +struct entry +tester (int len; char data[len][len], int len) +@{ + /* @r{@dots{}} */ +@} +@end smallexample + +@cindex parameter forward declaration +The @samp{int len} before the semicolon is a @dfn{parameter forward +declaration}, and it serves the purpose of making the name @code{len} +known when the declaration of @code{data} is parsed. + +You can write any number of such parameter forward declarations in the +parameter list. They can be separated by commas or semicolons, but the +last one must end with a semicolon, which is followed by the ``real'' +parameter declarations. Each forward declaration must match a ``real'' +declaration in parameter name and data type. ISO C99 does not support +parameter forward declarations. + +@node Variadic Macros +@section Macros with a Variable Number of Arguments. +@cindex variable number of arguments +@cindex macro with variable arguments +@cindex rest argument (in macro) +@cindex variadic macros + +In the ISO C standard of 1999, a macro can be declared to accept a +variable number of arguments much as a function can. The syntax for +defining the macro is similar to that of a function. Here is an +example: + +@smallexample +#define debug(format, ...) fprintf (stderr, format, __VA_ARGS__) +@end smallexample + +Here @samp{@dots{}} is a @dfn{variable argument}. In the invocation of +such a macro, it represents the zero or more tokens until the closing +parenthesis that ends the invocation, including any commas. This set of +tokens replaces the identifier @code{__VA_ARGS__} in the macro body +wherever it appears. See the CPP manual for more information. + +GCC has long supported variadic macros, and used a different syntax that +allowed you to give a name to the variable arguments just like any other +argument. Here is an example: + +@smallexample +#define debug(format, args...) fprintf (stderr, format, args) +@end smallexample + +This is in all ways equivalent to the ISO C example above, but arguably +more readable and descriptive. + +GNU CPP has two further variadic macro extensions, and permits them to +be used with either of the above forms of macro definition. + +In standard C, you are not allowed to leave the variable argument out +entirely; but you are allowed to pass an empty argument. For example, +this invocation is invalid in ISO C, because there is no comma after +the string: + +@smallexample +debug ("A message") +@end smallexample + +GNU CPP permits you to completely omit the variable arguments in this +way. In the above examples, the compiler would complain, though since +the expansion of the macro still has the extra comma after the format +string. + +To help solve this problem, CPP behaves specially for variable arguments +used with the token paste operator, @samp{##}. If instead you write + +@smallexample +#define debug(format, ...) fprintf (stderr, format, ## __VA_ARGS__) +@end smallexample + +and if the variable arguments are omitted or empty, the @samp{##} +operator causes the preprocessor to remove the comma before it. If you +do provide some variable arguments in your macro invocation, GNU CPP +does not complain about the paste operation and instead places the +variable arguments after the comma. Just like any other pasted macro +argument, these arguments are not macro expanded. + +@node Escaped Newlines +@section Slightly Looser Rules for Escaped Newlines +@cindex escaped newlines +@cindex newlines (escaped) + +Recently, the preprocessor has relaxed its treatment of escaped +newlines. Previously, the newline had to immediately follow a +backslash. The current implementation allows whitespace in the form +of spaces, horizontal and vertical tabs, and form feeds between the +backslash and the subsequent newline. The preprocessor issues a +warning, but treats it as a valid escaped newline and combines the two +lines to form a single logical line. This works within comments and +tokens, as well as between tokens. Comments are @emph{not} treated as +whitespace for the purposes of this relaxation, since they have not +yet been replaced with spaces. + +@node Subscripting +@section Non-Lvalue Arrays May Have Subscripts +@cindex subscripting +@cindex arrays, non-lvalue + +@cindex subscripting and function values +In ISO C99, arrays that are not lvalues still decay to pointers, and +may be subscripted, although they may not be modified or used after +the next sequence point and the unary @samp{&} operator may not be +applied to them. As an extension, GCC allows such arrays to be +subscripted in C90 mode, though otherwise they do not decay to +pointers outside C99 mode. For example, +this is valid in GNU C though not valid in C90: + +@smallexample +@group +struct foo @{int a[4];@}; + +struct foo f(); + +bar (int index) +@{ + return f().a[index]; +@} +@end group +@end smallexample + +@node Pointer Arith +@section Arithmetic on @code{void}- and Function-Pointers +@cindex void pointers, arithmetic +@cindex void, size of pointer to +@cindex function pointers, arithmetic +@cindex function, size of pointer to + +In GNU C, addition and subtraction operations are supported on pointers to +@code{void} and on pointers to functions. This is done by treating the +size of a @code{void} or of a function as 1. + +A consequence of this is that @code{sizeof} is also allowed on @code{void} +and on function types, and returns 1. + +@opindex Wpointer-arith +The option @option{-Wpointer-arith} requests a warning if these extensions +are used. + +@node Initializers +@section Non-Constant Initializers +@cindex initializers, non-constant +@cindex non-constant initializers + +As in standard C++ and ISO C99, the elements of an aggregate initializer for an +automatic variable are not required to be constant expressions in GNU C@. +Here is an example of an initializer with run-time varying elements: + +@smallexample +foo (float f, float g) +@{ + float beat_freqs[2] = @{ f-g, f+g @}; + /* @r{@dots{}} */ +@} +@end smallexample + +@node Compound Literals +@section Compound Literals +@cindex constructor expressions +@cindex initializations in expressions +@cindex structures, constructor expression +@cindex expressions, constructor +@cindex compound literals +@c The GNU C name for what C99 calls compound literals was "constructor expressions". + +ISO C99 supports compound literals. A compound literal looks like +a cast containing an initializer. Its value is an object of the +type specified in the cast, containing the elements specified in +the initializer; it is an lvalue. As an extension, GCC supports +compound literals in C90 mode and in C++. + +Usually, the specified type is a structure. Assume that +@code{struct foo} and @code{structure} are declared as shown: + +@smallexample +struct foo @{int a; char b[2];@} structure; +@end smallexample + +@noindent +Here is an example of constructing a @code{struct foo} with a compound literal: + +@smallexample +structure = ((struct foo) @{x + y, 'a', 0@}); +@end smallexample + +@noindent +This is equivalent to writing the following: + +@smallexample +@{ + struct foo temp = @{x + y, 'a', 0@}; + structure = temp; +@} +@end smallexample + +You can also construct an array. If all the elements of the compound literal +are (made up of) simple constant expressions, suitable for use in +initializers of objects of static storage duration, then the compound +literal can be coerced to a pointer to its first element and used in +such an initializer, as shown here: + +@smallexample +char **foo = (char *[]) @{ "x", "y", "z" @}; +@end smallexample + +Compound literals for scalar types and union types are is +also allowed, but then the compound literal is equivalent +to a cast. + +As a GNU extension, GCC allows initialization of objects with static storage +duration by compound literals (which is not possible in ISO C99, because +the initializer is not a constant). +It is handled as if the object was initialized only with the bracket +enclosed list if the types of the compound literal and the object match. +The initializer list of the compound literal must be constant. +If the object being initialized has array type of unknown size, the size is +determined by compound literal size. + +@smallexample +static struct foo x = (struct foo) @{1, 'a', 'b'@}; +static int y[] = (int []) @{1, 2, 3@}; +static int z[] = (int [3]) @{1@}; +@end smallexample + +@noindent +The above lines are equivalent to the following: +@smallexample +static struct foo x = @{1, 'a', 'b'@}; +static int y[] = @{1, 2, 3@}; +static int z[] = @{1, 0, 0@}; +@end smallexample + +@node Designated Inits +@section Designated Initializers +@cindex initializers with labeled elements +@cindex labeled elements in initializers +@cindex case labels in initializers +@cindex designated initializers + +Standard C90 requires the elements of an initializer to appear in a fixed +order, the same as the order of the elements in the array or structure +being initialized. + +In ISO C99 you can give the elements in any order, specifying the array +indices or structure field names they apply to, and GNU C allows this as +an extension in C90 mode as well. This extension is not +implemented in GNU C++. + +To specify an array index, write +@samp{[@var{index}] =} before the element value. For example, + +@smallexample +int a[6] = @{ [4] = 29, [2] = 15 @}; +@end smallexample + +@noindent +is equivalent to + +@smallexample +int a[6] = @{ 0, 0, 15, 0, 29, 0 @}; +@end smallexample + +@noindent +The index values must be constant expressions, even if the array being +initialized is automatic. + +An alternative syntax for this which has been obsolete since GCC 2.5 but +GCC still accepts is to write @samp{[@var{index}]} before the element +value, with no @samp{=}. + +To initialize a range of elements to the same value, write +@samp{[@var{first} ... @var{last}] = @var{value}}. This is a GNU +extension. For example, + +@smallexample +int widths[] = @{ [0 ... 9] = 1, [10 ... 99] = 2, [100] = 3 @}; +@end smallexample + +@noindent +If the value in it has side-effects, the side-effects will happen only once, +not for each initialized field by the range initializer. + +@noindent +Note that the length of the array is the highest value specified +plus one. + +In a structure initializer, specify the name of a field to initialize +with @samp{.@var{fieldname} =} before the element value. For example, +given the following structure, + +@smallexample +struct point @{ int x, y; @}; +@end smallexample + +@noindent +the following initialization + +@smallexample +struct point p = @{ .y = yvalue, .x = xvalue @}; +@end smallexample + +@noindent +is equivalent to + +@smallexample +struct point p = @{ xvalue, yvalue @}; +@end smallexample + +Another syntax which has the same meaning, obsolete since GCC 2.5, is +@samp{@var{fieldname}:}, as shown here: + +@smallexample +struct point p = @{ y: yvalue, x: xvalue @}; +@end smallexample + +@cindex designators +The @samp{[@var{index}]} or @samp{.@var{fieldname}} is known as a +@dfn{designator}. You can also use a designator (or the obsolete colon +syntax) when initializing a union, to specify which element of the union +should be used. For example, + +@smallexample +union foo @{ int i; double d; @}; + +union foo f = @{ .d = 4 @}; +@end smallexample + +@noindent +will convert 4 to a @code{double} to store it in the union using +the second element. By contrast, casting 4 to type @code{union foo} +would store it into the union as the integer @code{i}, since it is +an integer. (@xref{Cast to Union}.) + +You can combine this technique of naming elements with ordinary C +initialization of successive elements. Each initializer element that +does not have a designator applies to the next consecutive element of the +array or structure. For example, + +@smallexample +int a[6] = @{ [1] = v1, v2, [4] = v4 @}; +@end smallexample + +@noindent +is equivalent to + +@smallexample +int a[6] = @{ 0, v1, v2, 0, v4, 0 @}; +@end smallexample + +Labeling the elements of an array initializer is especially useful +when the indices are characters or belong to an @code{enum} type. +For example: + +@smallexample +int whitespace[256] + = @{ [' '] = 1, ['\t'] = 1, ['\h'] = 1, + ['\f'] = 1, ['\n'] = 1, ['\r'] = 1 @}; +@end smallexample + +@cindex designator lists +You can also write a series of @samp{.@var{fieldname}} and +@samp{[@var{index}]} designators before an @samp{=} to specify a +nested subobject to initialize; the list is taken relative to the +subobject corresponding to the closest surrounding brace pair. For +example, with the @samp{struct point} declaration above: + +@smallexample +struct point ptarray[10] = @{ [2].y = yv2, [2].x = xv2, [0].x = xv0 @}; +@end smallexample + +@noindent +If the same field is initialized multiple times, it will have value from +the last initialization. If any such overridden initialization has +side-effect, it is unspecified whether the side-effect happens or not. +Currently, GCC will discard them and issue a warning. + +@node Case Ranges +@section Case Ranges +@cindex case ranges +@cindex ranges in case statements + +You can specify a range of consecutive values in a single @code{case} label, +like this: + +@smallexample +case @var{low} ... @var{high}: +@end smallexample + +@noindent +This has the same effect as the proper number of individual @code{case} +labels, one for each integer value from @var{low} to @var{high}, inclusive. + +This feature is especially useful for ranges of ASCII character codes: + +@smallexample +case 'A' ... 'Z': +@end smallexample + +@strong{Be careful:} Write spaces around the @code{...}, for otherwise +it may be parsed wrong when you use it with integer values. For example, +write this: + +@smallexample +case 1 ... 5: +@end smallexample + +@noindent +rather than this: + +@smallexample +case 1...5: +@end smallexample + +@node Cast to Union +@section Cast to a Union Type +@cindex cast to a union +@cindex union, casting to a + +A cast to union type is similar to other casts, except that the type +specified is a union type. You can specify the type either with +@code{union @var{tag}} or with a typedef name. A cast to union is actually +a constructor though, not a cast, and hence does not yield an lvalue like +normal casts. (@xref{Compound Literals}.) + +The types that may be cast to the union type are those of the members +of the union. Thus, given the following union and variables: + +@smallexample +union foo @{ int i; double d; @}; +int x; +double y; +@end smallexample + +@noindent +both @code{x} and @code{y} can be cast to type @code{union foo}. + +Using the cast as the right-hand side of an assignment to a variable of +union type is equivalent to storing in a member of the union: + +@smallexample +union foo u; +/* @r{@dots{}} */ +u = (union foo) x @equiv{} u.i = x +u = (union foo) y @equiv{} u.d = y +@end smallexample + +You can also use the union cast as a function argument: + +@smallexample +void hack (union foo); +/* @r{@dots{}} */ +hack ((union foo) x); +@end smallexample + +@node Mixed Declarations +@section Mixed Declarations and Code +@cindex mixed declarations and code +@cindex declarations, mixed with code +@cindex code, mixed with declarations + +ISO C99 and ISO C++ allow declarations and code to be freely mixed +within compound statements. As an extension, GCC also allows this in +C90 mode. For example, you could do: + +@smallexample +int i; +/* @r{@dots{}} */ +i++; +int j = i + 2; +@end smallexample + +Each identifier is visible from where it is declared until the end of +the enclosing block. + +@node Function Attributes +@section Declaring Attributes of Functions +@cindex function attributes +@cindex declaring attributes of functions +@cindex functions that never return +@cindex functions that return more than once +@cindex functions that have no side effects +@cindex functions in arbitrary sections +@cindex functions that behave like malloc +@cindex @code{volatile} applied to function +@cindex @code{const} applied to function +@cindex functions with @code{printf}, @code{scanf}, @code{strftime} or @code{strfmon} style arguments +@cindex functions with non-null pointer arguments +@cindex functions that are passed arguments in registers on the 386 +@cindex functions that pop the argument stack on the 386 +@cindex functions that do not pop the argument stack on the 386 +@cindex functions that have different compilation options on the 386 +@cindex functions that have different optimization options +@cindex functions that are dynamically resolved + +In GNU C, you declare certain things about functions called in your program +which help the compiler optimize function calls and check your code more +carefully. + +The keyword @code{__attribute__} allows you to specify special +attributes when making a declaration. This keyword is followed by an +attribute specification inside double parentheses. The following +attributes are currently defined for functions on all targets: +@code{aligned}, @code{alloc_size}, @code{noreturn}, +@code{returns_twice}, @code{noinline}, @code{noclone}, +@code{always_inline}, @code{flatten}, @code{pure}, @code{const}, +@code{nothrow}, @code{sentinel}, @code{format}, @code{format_arg}, +@code{no_instrument_function}, @code{no_split_stack}, +@code{section}, @code{constructor}, +@code{destructor}, @code{used}, @code{unused}, @code{deprecated}, +@code{weak}, @code{malloc}, @code{alias}, @code{ifunc}, +@code{warn_unused_result}, @code{nonnull}, @code{gnu_inline}, +@code{externally_visible}, @code{hot}, @code{cold}, @code{artificial}, +@code{error} and @code{warning}. Several other attributes are defined +for functions on particular target systems. Other attributes, +including @code{section} are supported for variables declarations +(@pxref{Variable Attributes}) and for types (@pxref{Type Attributes}). + +GCC plugins may provide their own attributes. + +You may also specify attributes with @samp{__} preceding and following +each keyword. This allows you to use them in header files without +being concerned about a possible macro of the same name. For example, +you may use @code{__noreturn__} instead of @code{noreturn}. + +@xref{Attribute Syntax}, for details of the exact syntax for using +attributes. + +@table @code +@c Keep this table alphabetized by attribute name. Treat _ as space. + +@item alias ("@var{target}") +@cindex @code{alias} attribute +The @code{alias} attribute causes the declaration to be emitted as an +alias for another symbol, which must be specified. For instance, + +@smallexample +void __f () @{ /* @r{Do something.} */; @} +void f () __attribute__ ((weak, alias ("__f"))); +@end smallexample + +defines @samp{f} to be a weak alias for @samp{__f}. In C++, the +mangled name for the target must be used. It is an error if @samp{__f} +is not defined in the same translation unit. + +Not all target machines support this attribute. + +@item aligned (@var{alignment}) +@cindex @code{aligned} attribute +This attribute specifies a minimum alignment for the function, +measured in bytes. + +You cannot use this attribute to decrease the alignment of a function, +only to increase it. However, when you explicitly specify a function +alignment this will override the effect of the +@option{-falign-functions} (@pxref{Optimize Options}) option for this +function. + +Note that the effectiveness of @code{aligned} attributes may be +limited by inherent limitations in your linker. On many systems, the +linker is only able to arrange for functions to be aligned up to a +certain maximum alignment. (For some linkers, the maximum supported +alignment may be very very small.) See your linker documentation for +further information. + +The @code{aligned} attribute can also be used for variables and fields +(@pxref{Variable Attributes}.) + +@item alloc_size +@cindex @code{alloc_size} attribute +The @code{alloc_size} attribute is used to tell the compiler that the +function return value points to memory, where the size is given by +one or two of the functions parameters. GCC uses this +information to improve the correctness of @code{__builtin_object_size}. + +The function parameter(s) denoting the allocated size are specified by +one or two integer arguments supplied to the attribute. The allocated size +is either the value of the single function argument specified or the product +of the two function arguments specified. Argument numbering starts at +one. + +For instance, + +@smallexample +void* my_calloc(size_t, size_t) __attribute__((alloc_size(1,2))) +void my_realloc(void*, size_t) __attribute__((alloc_size(2))) +@end smallexample + +declares that my_calloc will return memory of the size given by +the product of parameter 1 and 2 and that my_realloc will return memory +of the size given by parameter 2. + +@item always_inline +@cindex @code{always_inline} function attribute +Generally, functions are not inlined unless optimization is specified. +For functions declared inline, this attribute inlines the function even +if no optimization level was specified. + +@item gnu_inline +@cindex @code{gnu_inline} function attribute +This attribute should be used with a function which is also declared +with the @code{inline} keyword. It directs GCC to treat the function +as if it were defined in gnu90 mode even when compiling in C99 or +gnu99 mode. + +If the function is declared @code{extern}, then this definition of the +function is used only for inlining. In no case is the function +compiled as a standalone function, not even if you take its address +explicitly. Such an address becomes an external reference, as if you +had only declared the function, and had not defined it. This has +almost the effect of a macro. The way to use this is to put a +function definition in a header file with this attribute, and put +another copy of the function, without @code{extern}, in a library +file. The definition in the header file will cause most calls to the +function to be inlined. If any uses of the function remain, they will +refer to the single copy in the library. Note that the two +definitions of the functions need not be precisely the same, although +if they do not have the same effect your program may behave oddly. + +In C, if the function is neither @code{extern} nor @code{static}, then +the function is compiled as a standalone function, as well as being +inlined where possible. + +This is how GCC traditionally handled functions declared +@code{inline}. Since ISO C99 specifies a different semantics for +@code{inline}, this function attribute is provided as a transition +measure and as a useful feature in its own right. This attribute is +available in GCC 4.1.3 and later. It is available if either of the +preprocessor macros @code{__GNUC_GNU_INLINE__} or +@code{__GNUC_STDC_INLINE__} are defined. @xref{Inline,,An Inline +Function is As Fast As a Macro}. + +In C++, this attribute does not depend on @code{extern} in any way, +but it still requires the @code{inline} keyword to enable its special +behavior. + +@item artificial +@cindex @code{artificial} function attribute +This attribute is useful for small inline wrappers which if possible +should appear during debugging as a unit, depending on the debug +info format it will either mean marking the function as artificial +or using the caller location for all instructions within the inlined +body. + +@item bank_switch +@cindex interrupt handler functions +When added to an interrupt handler with the M32C port, causes the +prologue and epilogue to use bank switching to preserve the registers +rather than saving them on the stack. + +@item flatten +@cindex @code{flatten} function attribute +Generally, inlining into a function is limited. For a function marked with +this attribute, every call inside this function will be inlined, if possible. +Whether the function itself is considered for inlining depends on its size and +the current inlining parameters. + +@item error ("@var{message}") +@cindex @code{error} function attribute +If this attribute is used on a function declaration and a call to such a function +is not eliminated through dead code elimination or other optimizations, an error +which will include @var{message} will be diagnosed. This is useful +for compile time checking, especially together with @code{__builtin_constant_p} +and inline functions where checking the inline function arguments is not +possible through @code{extern char [(condition) ? 1 : -1];} tricks. +While it is possible to leave the function undefined and thus invoke +a link failure, when using this attribute the problem will be diagnosed +earlier and with exact location of the call even in presence of inline +functions or when not emitting debugging information. + +@item warning ("@var{message}") +@cindex @code{warning} function attribute +If this attribute is used on a function declaration and a call to such a function +is not eliminated through dead code elimination or other optimizations, a warning +which will include @var{message} will be diagnosed. This is useful +for compile time checking, especially together with @code{__builtin_constant_p} +and inline functions. While it is possible to define the function with +a message in @code{.gnu.warning*} section, when using this attribute the problem +will be diagnosed earlier and with exact location of the call even in presence +of inline functions or when not emitting debugging information. + +@item cdecl +@cindex functions that do pop the argument stack on the 386 +@opindex mrtd +On the Intel 386, the @code{cdecl} attribute causes the compiler to +assume that the calling function will pop off the stack space used to +pass arguments. This is +useful to override the effects of the @option{-mrtd} switch. + +@item const +@cindex @code{const} function attribute +Many functions do not examine any values except their arguments, and +have no effects except the return value. Basically this is just slightly +more strict class than the @code{pure} attribute below, since function is not +allowed to read global memory. + +@cindex pointer arguments +Note that a function that has pointer arguments and examines the data +pointed to must @emph{not} be declared @code{const}. Likewise, a +function that calls a non-@code{const} function usually must not be +@code{const}. It does not make sense for a @code{const} function to +return @code{void}. + +The attribute @code{const} is not implemented in GCC versions earlier +than 2.5. An alternative way to declare that a function has no side +effects, which works in the current version and in some older versions, +is as follows: + +@smallexample +typedef int intfn (); + +extern const intfn square; +@end smallexample + +This approach does not work in GNU C++ from 2.6.0 on, since the language +specifies that the @samp{const} must be attached to the return value. + +@item constructor +@itemx destructor +@itemx constructor (@var{priority}) +@itemx destructor (@var{priority}) +@cindex @code{constructor} function attribute +@cindex @code{destructor} function attribute +The @code{constructor} attribute causes the function to be called +automatically before execution enters @code{main ()}. Similarly, the +@code{destructor} attribute causes the function to be called +automatically after @code{main ()} has completed or @code{exit ()} has +been called. Functions with these attributes are useful for +initializing data that will be used implicitly during the execution of +the program. + +You may provide an optional integer priority to control the order in +which constructor and destructor functions are run. A constructor +with a smaller priority number runs before a constructor with a larger +priority number; the opposite relationship holds for destructors. So, +if you have a constructor that allocates a resource and a destructor +that deallocates the same resource, both functions typically have the +same priority. The priorities for constructor and destructor +functions are the same as those specified for namespace-scope C++ +objects (@pxref{C++ Attributes}). + +These attributes are not currently implemented for Objective-C@. + +@item deprecated +@itemx deprecated (@var{msg}) +@cindex @code{deprecated} attribute. +The @code{deprecated} attribute results in a warning if the function +is used anywhere in the source file. This is useful when identifying +functions that are expected to be removed in a future version of a +program. The warning also includes the location of the declaration +of the deprecated function, to enable users to easily find further +information about why the function is deprecated, or what they should +do instead. Note that the warnings only occurs for uses: + +@smallexample +int old_fn () __attribute__ ((deprecated)); +int old_fn (); +int (*fn_ptr)() = old_fn; +@end smallexample + +results in a warning on line 3 but not line 2. The optional msg +argument, which must be a string, will be printed in the warning if +present. + +The @code{deprecated} attribute can also be used for variables and +types (@pxref{Variable Attributes}, @pxref{Type Attributes}.) + +@item disinterrupt +@cindex @code{disinterrupt} attribute +On MeP targets, this attribute causes the compiler to emit +instructions to disable interrupts for the duration of the given +function. + +@item dllexport +@cindex @code{__declspec(dllexport)} +On Microsoft Windows targets and Symbian OS targets the +@code{dllexport} attribute causes the compiler to provide a global +pointer to a pointer in a DLL, so that it can be referenced with the +@code{dllimport} attribute. On Microsoft Windows targets, the pointer +name is formed by combining @code{_imp__} and the function or variable +name. + +You can use @code{__declspec(dllexport)} as a synonym for +@code{__attribute__ ((dllexport))} for compatibility with other +compilers. + +On systems that support the @code{visibility} attribute, this +attribute also implies ``default'' visibility. It is an error to +explicitly specify any other visibility. + +In previous versions of GCC, the @code{dllexport} attribute was ignored +for inlined functions, unless the @option{-fkeep-inline-functions} flag +had been used. The default behaviour now is to emit all dllexported +inline functions; however, this can cause object file-size bloat, in +which case the old behaviour can be restored by using +@option{-fno-keep-inline-dllexport}. + +The attribute is also ignored for undefined symbols. + +When applied to C++ classes, the attribute marks defined non-inlined +member functions and static data members as exports. Static consts +initialized in-class are not marked unless they are also defined +out-of-class. + +For Microsoft Windows targets there are alternative methods for +including the symbol in the DLL's export table such as using a +@file{.def} file with an @code{EXPORTS} section or, with GNU ld, using +the @option{--export-all} linker flag. + +@item dllimport +@cindex @code{__declspec(dllimport)} +On Microsoft Windows and Symbian OS targets, the @code{dllimport} +attribute causes the compiler to reference a function or variable via +a global pointer to a pointer that is set up by the DLL exporting the +symbol. The attribute implies @code{extern}. On Microsoft Windows +targets, the pointer name is formed by combining @code{_imp__} and the +function or variable name. + +You can use @code{__declspec(dllimport)} as a synonym for +@code{__attribute__ ((dllimport))} for compatibility with other +compilers. + +On systems that support the @code{visibility} attribute, this +attribute also implies ``default'' visibility. It is an error to +explicitly specify any other visibility. + +Currently, the attribute is ignored for inlined functions. If the +attribute is applied to a symbol @emph{definition}, an error is reported. +If a symbol previously declared @code{dllimport} is later defined, the +attribute is ignored in subsequent references, and a warning is emitted. +The attribute is also overridden by a subsequent declaration as +@code{dllexport}. + +When applied to C++ classes, the attribute marks non-inlined +member functions and static data members as imports. However, the +attribute is ignored for virtual methods to allow creation of vtables +using thunks. + +On the SH Symbian OS target the @code{dllimport} attribute also has +another affect---it can cause the vtable and run-time type information +for a class to be exported. This happens when the class has a +dllimport'ed constructor or a non-inline, non-pure virtual function +and, for either of those two conditions, the class also has an inline +constructor or destructor and has a key function that is defined in +the current translation unit. + +For Microsoft Windows based targets the use of the @code{dllimport} +attribute on functions is not necessary, but provides a small +performance benefit by eliminating a thunk in the DLL@. The use of the +@code{dllimport} attribute on imported variables was required on older +versions of the GNU linker, but can now be avoided by passing the +@option{--enable-auto-import} switch to the GNU linker. As with +functions, using the attribute for a variable eliminates a thunk in +the DLL@. + +One drawback to using this attribute is that a pointer to a +@emph{variable} marked as @code{dllimport} cannot be used as a constant +address. However, a pointer to a @emph{function} with the +@code{dllimport} attribute can be used as a constant initializer; in +this case, the address of a stub function in the import lib is +referenced. On Microsoft Windows targets, the attribute can be disabled +for functions by setting the @option{-mnop-fun-dllimport} flag. + +@item eightbit_data +@cindex eight bit data on the H8/300, H8/300H, and H8S +Use this attribute on the H8/300, H8/300H, and H8S to indicate that the specified +variable should be placed into the eight bit data section. +The compiler will generate more efficient code for certain operations +on data in the eight bit data area. Note the eight bit data area is limited to +256 bytes of data. + +You must use GAS and GLD from GNU binutils version 2.7 or later for +this attribute to work correctly. + +@item exception_handler +@cindex exception handler functions on the Blackfin processor +Use this attribute on the Blackfin to indicate that the specified function +is an exception handler. The compiler will generate function entry and +exit sequences suitable for use in an exception handler when this +attribute is present. + +@item externally_visible +@cindex @code{externally_visible} attribute. +This attribute, attached to a global variable or function, nullifies +the effect of the @option{-fwhole-program} command-line option, so the +object remains visible outside the current compilation unit. If @option{-fwhole-program} is used together with @option{-flto} and @command{gold} is used as the linker plugin, @code{externally_visible} attributes are automatically added to functions (not variable yet due to a current @command{gold} issue) that are accessed outside of LTO objects according to resolution file produced by @command{gold}. For other linkers that cannot generate resolution file, explicit @code{externally_visible} attributes are still necessary. + +@item far +@cindex functions which handle memory bank switching +On 68HC11 and 68HC12 the @code{far} attribute causes the compiler to +use a calling convention that takes care of switching memory banks when +entering and leaving a function. This calling convention is also the +default when using the @option{-mlong-calls} option. + +On 68HC12 the compiler will use the @code{call} and @code{rtc} instructions +to call and return from a function. + +On 68HC11 the compiler will generate a sequence of instructions +to invoke a board-specific routine to switch the memory bank and call the +real function. The board-specific routine simulates a @code{call}. +At the end of a function, it will jump to a board-specific routine +instead of using @code{rts}. The board-specific return routine simulates +the @code{rtc}. + +On MeP targets this causes the compiler to use a calling convention +which assumes the called function is too far away for the built-in +addressing modes. + +@item fast_interrupt +@cindex interrupt handler functions +Use this attribute on the M32C and RX ports to indicate that the specified +function is a fast interrupt handler. This is just like the +@code{interrupt} attribute, except that @code{freit} is used to return +instead of @code{reit}. + +@item fastcall +@cindex functions that pop the argument stack on the 386 +On the Intel 386, the @code{fastcall} attribute causes the compiler to +pass the first argument (if of integral type) in the register ECX and +the second argument (if of integral type) in the register EDX@. Subsequent +and other typed arguments are passed on the stack. The called function will +pop the arguments off the stack. If the number of arguments is variable all +arguments are pushed on the stack. + +@item thiscall +@cindex functions that pop the argument stack on the 386 +On the Intel 386, the @code{thiscall} attribute causes the compiler to +pass the first argument (if of integral type) in the register ECX. +Subsequent and other typed arguments are passed on the stack. The called +function will pop the arguments off the stack. +If the number of arguments is variable all arguments are pushed on the +stack. +The @code{thiscall} attribute is intended for C++ non-static member functions. +As gcc extension this calling convention can be used for C-functions +and for static member methods. + +@item format (@var{archetype}, @var{string-index}, @var{first-to-check}) +@cindex @code{format} function attribute +@opindex Wformat +The @code{format} attribute specifies that a function takes @code{printf}, +@code{scanf}, @code{strftime} or @code{strfmon} style arguments which +should be type-checked against a format string. For example, the +declaration: + +@smallexample +extern int +my_printf (void *my_object, const char *my_format, ...) + __attribute__ ((format (printf, 2, 3))); +@end smallexample + +@noindent +causes the compiler to check the arguments in calls to @code{my_printf} +for consistency with the @code{printf} style format string argument +@code{my_format}. + +The parameter @var{archetype} determines how the format string is +interpreted, and should be @code{printf}, @code{scanf}, @code{strftime}, +@code{gnu_printf}, @code{gnu_scanf}, @code{gnu_strftime} or +@code{strfmon}. (You can also use @code{__printf__}, +@code{__scanf__}, @code{__strftime__} or @code{__strfmon__}.) On +MinGW targets, @code{ms_printf}, @code{ms_scanf}, and +@code{ms_strftime} are also present. +@var{archtype} values such as @code{printf} refer to the formats accepted +by the system's C run-time library, while @code{gnu_} values always refer +to the formats accepted by the GNU C Library. On Microsoft Windows +targets, @code{ms_} values refer to the formats accepted by the +@file{msvcrt.dll} library. +The parameter @var{string-index} +specifies which argument is the format string argument (starting +from 1), while @var{first-to-check} is the number of the first +argument to check against the format string. For functions +where the arguments are not available to be checked (such as +@code{vprintf}), specify the third parameter as zero. In this case the +compiler only checks the format string for consistency. For +@code{strftime} formats, the third parameter is required to be zero. +Since non-static C++ methods have an implicit @code{this} argument, the +arguments of such methods should be counted from two, not one, when +giving values for @var{string-index} and @var{first-to-check}. + +In the example above, the format string (@code{my_format}) is the second +argument of the function @code{my_print}, and the arguments to check +start with the third argument, so the correct parameters for the format +attribute are 2 and 3. + +@opindex ffreestanding +@opindex fno-builtin +The @code{format} attribute allows you to identify your own functions +which take format strings as arguments, so that GCC can check the +calls to these functions for errors. The compiler always (unless +@option{-ffreestanding} or @option{-fno-builtin} is used) checks formats +for the standard library functions @code{printf}, @code{fprintf}, +@code{sprintf}, @code{scanf}, @code{fscanf}, @code{sscanf}, @code{strftime}, +@code{vprintf}, @code{vfprintf} and @code{vsprintf} whenever such +warnings are requested (using @option{-Wformat}), so there is no need to +modify the header file @file{stdio.h}. In C99 mode, the functions +@code{snprintf}, @code{vsnprintf}, @code{vscanf}, @code{vfscanf} and +@code{vsscanf} are also checked. Except in strictly conforming C +standard modes, the X/Open function @code{strfmon} is also checked as +are @code{printf_unlocked} and @code{fprintf_unlocked}. +@xref{C Dialect Options,,Options Controlling C Dialect}. + +For Objective-C dialects, @code{NSString} (or @code{__NSString__}) is +recognized in the same context. Declarations including these format attributes +will be parsed for correct syntax, however the result of checking of such format +strings is not yet defined, and will not be carried out by this version of the +compiler. + +The target may also provide additional types of format checks. +@xref{Target Format Checks,,Format Checks Specific to Particular +Target Machines}. + +@item format_arg (@var{string-index}) +@cindex @code{format_arg} function attribute +@opindex Wformat-nonliteral +The @code{format_arg} attribute specifies that a function takes a format +string for a @code{printf}, @code{scanf}, @code{strftime} or +@code{strfmon} style function and modifies it (for example, to translate +it into another language), so the result can be passed to a +@code{printf}, @code{scanf}, @code{strftime} or @code{strfmon} style +function (with the remaining arguments to the format function the same +as they would have been for the unmodified string). For example, the +declaration: + +@smallexample +extern char * +my_dgettext (char *my_domain, const char *my_format) + __attribute__ ((format_arg (2))); +@end smallexample + +@noindent +causes the compiler to check the arguments in calls to a @code{printf}, +@code{scanf}, @code{strftime} or @code{strfmon} type function, whose +format string argument is a call to the @code{my_dgettext} function, for +consistency with the format string argument @code{my_format}. If the +@code{format_arg} attribute had not been specified, all the compiler +could tell in such calls to format functions would be that the format +string argument is not constant; this would generate a warning when +@option{-Wformat-nonliteral} is used, but the calls could not be checked +without the attribute. + +The parameter @var{string-index} specifies which argument is the format +string argument (starting from one). Since non-static C++ methods have +an implicit @code{this} argument, the arguments of such methods should +be counted from two. + +The @code{format-arg} attribute allows you to identify your own +functions which modify format strings, so that GCC can check the +calls to @code{printf}, @code{scanf}, @code{strftime} or @code{strfmon} +type function whose operands are a call to one of your own function. +The compiler always treats @code{gettext}, @code{dgettext}, and +@code{dcgettext} in this manner except when strict ISO C support is +requested by @option{-ansi} or an appropriate @option{-std} option, or +@option{-ffreestanding} or @option{-fno-builtin} +is used. @xref{C Dialect Options,,Options +Controlling C Dialect}. + +For Objective-C dialects, the @code{format-arg} attribute may refer to an +@code{NSString} reference for compatibility with the @code{format} attribute +above. + +The target may also allow additional types in @code{format-arg} attributes. +@xref{Target Format Checks,,Format Checks Specific to Particular +Target Machines}. + +@item function_vector +@cindex calling functions through the function vector on H8/300, M16C, M32C and SH2A processors +Use this attribute on the H8/300, H8/300H, and H8S to indicate that the specified +function should be called through the function vector. Calling a +function through the function vector will reduce code size, however; +the function vector has a limited size (maximum 128 entries on the H8/300 +and 64 entries on the H8/300H and H8S) and shares space with the interrupt vector. + +In SH2A target, this attribute declares a function to be called using the +TBR relative addressing mode. The argument to this attribute is the entry +number of the same function in a vector table containing all the TBR +relative addressable functions. For the successful jump, register TBR +should contain the start address of this TBR relative vector table. +In the startup routine of the user application, user needs to care of this +TBR register initialization. The TBR relative vector table can have at +max 256 function entries. The jumps to these functions will be generated +using a SH2A specific, non delayed branch instruction JSR/N @@(disp8,TBR). +You must use GAS and GLD from GNU binutils version 2.7 or later for +this attribute to work correctly. + +Please refer the example of M16C target, to see the use of this +attribute while declaring a function, + +In an application, for a function being called once, this attribute will +save at least 8 bytes of code; and if other successive calls are being +made to the same function, it will save 2 bytes of code per each of these +calls. + +On M16C/M32C targets, the @code{function_vector} attribute declares a +special page subroutine call function. Use of this attribute reduces +the code size by 2 bytes for each call generated to the +subroutine. The argument to the attribute is the vector number entry +from the special page vector table which contains the 16 low-order +bits of the subroutine's entry address. Each vector table has special +page number (18 to 255) which are used in @code{jsrs} instruction. +Jump addresses of the routines are generated by adding 0x0F0000 (in +case of M16C targets) or 0xFF0000 (in case of M32C targets), to the 2 +byte addresses set in the vector table. Therefore you need to ensure +that all the special page vector routines should get mapped within the +address range 0x0F0000 to 0x0FFFFF (for M16C) and 0xFF0000 to 0xFFFFFF +(for M32C). + +In the following example 2 bytes will be saved for each call to +function @code{foo}. + +@smallexample +void foo (void) __attribute__((function_vector(0x18))); +void foo (void) +@{ +@} + +void bar (void) +@{ + foo(); +@} +@end smallexample + +If functions are defined in one file and are called in another file, +then be sure to write this declaration in both files. + +This attribute is ignored for R8C target. + +@item interrupt +@cindex interrupt handler functions +Use this attribute on the ARM, AVR, CRX, M32C, M32R/D, m68k, MeP, MIPS, +RX and Xstormy16 ports to indicate that the specified function is an +interrupt handler. The compiler will generate function entry and exit +sequences suitable for use in an interrupt handler when this attribute +is present. + +Note, interrupt handlers for the Blackfin, H8/300, H8/300H, H8S, MicroBlaze, +and SH processors can be specified via the @code{interrupt_handler} attribute. + +Note, on the AVR, interrupts will be enabled inside the function. + +Note, for the ARM, you can specify the kind of interrupt to be handled by +adding an optional parameter to the interrupt attribute like this: + +@smallexample +void f () __attribute__ ((interrupt ("IRQ"))); +@end smallexample + +Permissible values for this parameter are: IRQ, FIQ, SWI, ABORT and UNDEF@. + +On ARMv7-M the interrupt type is ignored, and the attribute means the function +may be called with a word aligned stack pointer. + +On MIPS targets, you can use the following attributes to modify the behavior +of an interrupt handler: +@table @code +@item use_shadow_register_set +@cindex @code{use_shadow_register_set} attribute +Assume that the handler uses a shadow register set, instead of +the main general-purpose registers. + +@item keep_interrupts_masked +@cindex @code{keep_interrupts_masked} attribute +Keep interrupts masked for the whole function. Without this attribute, +GCC tries to reenable interrupts for as much of the function as it can. + +@item use_debug_exception_return +@cindex @code{use_debug_exception_return} attribute +Return using the @code{deret} instruction. Interrupt handlers that don't +have this attribute return using @code{eret} instead. +@end table + +You can use any combination of these attributes, as shown below: +@smallexample +void __attribute__ ((interrupt)) v0 (); +void __attribute__ ((interrupt, use_shadow_register_set)) v1 (); +void __attribute__ ((interrupt, keep_interrupts_masked)) v2 (); +void __attribute__ ((interrupt, use_debug_exception_return)) v3 (); +void __attribute__ ((interrupt, use_shadow_register_set, + keep_interrupts_masked)) v4 (); +void __attribute__ ((interrupt, use_shadow_register_set, + use_debug_exception_return)) v5 (); +void __attribute__ ((interrupt, keep_interrupts_masked, + use_debug_exception_return)) v6 (); +void __attribute__ ((interrupt, use_shadow_register_set, + keep_interrupts_masked, + use_debug_exception_return)) v7 (); +@end smallexample + +@item ifunc ("@var{resolver}") +@cindex @code{ifunc} attribute +The @code{ifunc} attribute is used to mark a function as an indirect +function using the STT_GNU_IFUNC symbol type extension to the ELF +standard. This allows the resolution of the symbol value to be +determined dynamically at load time, and an optimized version of the +routine can be selected for the particular processor or other system +characteristics determined then. To use this attribute, first define +the implementation functions available, and a resolver function that +returns a pointer to the selected implementation function. The +implementation functions' declarations must match the API of the +function being implemented, the resolver's declaration is be a +function returning pointer to void function returning void: + +@smallexample +void *my_memcpy (void *dst, const void *src, size_t len) +@{ + @dots{} +@} + +static void (*resolve_memcpy (void)) (void) +@{ + return my_memcpy; // we'll just always select this routine +@} +@end smallexample + +The exported header file declaring the function the user calls would +contain: + +@smallexample +extern void *memcpy (void *, const void *, size_t); +@end smallexample + +allowing the user to call this as a regular function, unaware of the +implementation. Finally, the indirect function needs to be defined in +the same translation unit as the resolver function: + +@smallexample +void *memcpy (void *, const void *, size_t) + __attribute__ ((ifunc ("resolve_memcpy"))); +@end smallexample + +Indirect functions cannot be weak, and require a recent binutils (at +least version 2.20.1), and GNU C library (at least version 2.11.1). + +@item interrupt_handler +@cindex interrupt handler functions on the Blackfin, m68k, H8/300 and SH processors +Use this attribute on the Blackfin, m68k, H8/300, H8/300H, H8S, and SH to +indicate that the specified function is an interrupt handler. The compiler +will generate function entry and exit sequences suitable for use in an +interrupt handler when this attribute is present. + +@item interrupt_thread +@cindex interrupt thread functions on fido +Use this attribute on fido, a subarchitecture of the m68k, to indicate +that the specified function is an interrupt handler that is designed +to run as a thread. The compiler omits generate prologue/epilogue +sequences and replaces the return instruction with a @code{sleep} +instruction. This attribute is available only on fido. + +@item isr +@cindex interrupt service routines on ARM +Use this attribute on ARM to write Interrupt Service Routines. This is an +alias to the @code{interrupt} attribute above. + +@item kspisusp +@cindex User stack pointer in interrupts on the Blackfin +When used together with @code{interrupt_handler}, @code{exception_handler} +or @code{nmi_handler}, code will be generated to load the stack pointer +from the USP register in the function prologue. + +@item l1_text +@cindex @code{l1_text} function attribute +This attribute specifies a function to be placed into L1 Instruction +SRAM@. The function will be put into a specific section named @code{.l1.text}. +With @option{-mfdpic}, function calls with a such function as the callee +or caller will use inlined PLT. + +@item l2 +@cindex @code{l2} function attribute +On the Blackfin, this attribute specifies a function to be placed into L2 +SRAM. The function will be put into a specific section named +@code{.l1.text}. With @option{-mfdpic}, callers of such functions will use +an inlined PLT. + +@item leaf +@cindex @code{leaf} function attribute +Calls to external functions with this attribute must return to the current +compilation unit only by return or by exception handling. In particular, leaf +functions are not allowed to call callback function passed to it from the current +compilation unit or directly call functions exported by the unit or longjmp +into the unit. Leaf function might still call functions from other compilation +units and thus they are not necessarily leaf in the sense that they contain no +function calls at all. + +The attribute is intended for library functions to improve dataflow analysis. +The compiler takes the hint that any data not escaping the current compilation unit can +not be used or modified by the leaf function. For example, the @code{sin} function +is a leaf function, but @code{qsort} is not. + +Note that leaf functions might invoke signals and signal handlers might be +defined in the current compilation unit and use static variables. The only +compliant way to write such a signal handler is to declare such variables +@code{volatile}. + +The attribute has no effect on functions defined within the current compilation +unit. This is to allow easy merging of multiple compilation units into one, +for example, by using the link time optimization. For this reason the +attribute is not allowed on types to annotate indirect calls. + +@item long_call/short_call +@cindex indirect calls on ARM +This attribute specifies how a particular function is called on +ARM@. Both attributes override the @option{-mlong-calls} (@pxref{ARM Options}) +command-line switch and @code{#pragma long_calls} settings. The +@code{long_call} attribute indicates that the function might be far +away from the call site and require a different (more expensive) +calling sequence. The @code{short_call} attribute always places +the offset to the function from the call site into the @samp{BL} +instruction directly. + +@item longcall/shortcall +@cindex functions called via pointer on the RS/6000 and PowerPC +On the Blackfin, RS/6000 and PowerPC, the @code{longcall} attribute +indicates that the function might be far away from the call site and +require a different (more expensive) calling sequence. The +@code{shortcall} attribute indicates that the function is always close +enough for the shorter calling sequence to be used. These attributes +override both the @option{-mlongcall} switch and, on the RS/6000 and +PowerPC, the @code{#pragma longcall} setting. + +@xref{RS/6000 and PowerPC Options}, for more information on whether long +calls are necessary. + +@item long_call/near/far +@cindex indirect calls on MIPS +These attributes specify how a particular function is called on MIPS@. +The attributes override the @option{-mlong-calls} (@pxref{MIPS Options}) +command-line switch. The @code{long_call} and @code{far} attributes are +synonyms, and cause the compiler to always call +the function by first loading its address into a register, and then using +the contents of that register. The @code{near} attribute has the opposite +effect; it specifies that non-PIC calls should be made using the more +efficient @code{jal} instruction. + +@item malloc +@cindex @code{malloc} attribute +The @code{malloc} attribute is used to tell the compiler that a function +may be treated as if any non-@code{NULL} pointer it returns cannot +alias any other pointer valid when the function returns. +This will often improve optimization. +Standard functions with this property include @code{malloc} and +@code{calloc}. @code{realloc}-like functions have this property as +long as the old pointer is never referred to (including comparing it +to the new pointer) after the function returns a non-@code{NULL} +value. + +@item mips16/nomips16 +@cindex @code{mips16} attribute +@cindex @code{nomips16} attribute + +On MIPS targets, you can use the @code{mips16} and @code{nomips16} +function attributes to locally select or turn off MIPS16 code generation. +A function with the @code{mips16} attribute is emitted as MIPS16 code, +while MIPS16 code generation is disabled for functions with the +@code{nomips16} attribute. These attributes override the +@option{-mips16} and @option{-mno-mips16} options on the command line +(@pxref{MIPS Options}). + +When compiling files containing mixed MIPS16 and non-MIPS16 code, the +preprocessor symbol @code{__mips16} reflects the setting on the command line, +not that within individual functions. Mixed MIPS16 and non-MIPS16 code +may interact badly with some GCC extensions such as @code{__builtin_apply} +(@pxref{Constructing Calls}). + +@item model (@var{model-name}) +@cindex function addressability on the M32R/D +@cindex variable addressability on the IA-64 + +On the M32R/D, use this attribute to set the addressability of an +object, and of the code generated for a function. The identifier +@var{model-name} is one of @code{small}, @code{medium}, or +@code{large}, representing each of the code models. + +Small model objects live in the lower 16MB of memory (so that their +addresses can be loaded with the @code{ld24} instruction), and are +callable with the @code{bl} instruction. + +Medium model objects may live anywhere in the 32-bit address space (the +compiler will generate @code{seth/add3} instructions to load their addresses), +and are callable with the @code{bl} instruction. + +Large model objects may live anywhere in the 32-bit address space (the +compiler will generate @code{seth/add3} instructions to load their addresses), +and may not be reachable with the @code{bl} instruction (the compiler will +generate the much slower @code{seth/add3/jl} instruction sequence). + +On IA-64, use this attribute to set the addressability of an object. +At present, the only supported identifier for @var{model-name} is +@code{small}, indicating addressability via ``small'' (22-bit) +addresses (so that their addresses can be loaded with the @code{addl} +instruction). Caveat: such addressing is by definition not position +independent and hence this attribute must not be used for objects +defined by shared libraries. + +@item ms_abi/sysv_abi +@cindex @code{ms_abi} attribute +@cindex @code{sysv_abi} attribute + +On 64-bit x86_64-*-* targets, you can use an ABI attribute to indicate +which calling convention should be used for a function. The @code{ms_abi} +attribute tells the compiler to use the Microsoft ABI, while the +@code{sysv_abi} attribute tells the compiler to use the ABI used on +GNU/Linux and other systems. The default is to use the Microsoft ABI +when targeting Windows. On all other systems, the default is the AMD ABI. + +Note, the @code{ms_abi} attribute for Windows targets currently requires +the @option{-maccumulate-outgoing-args} option. + +@item callee_pop_aggregate_return (@var{number}) +@cindex @code{callee_pop_aggregate_return} attribute + +On 32-bit i?86-*-* targets, you can control by those attribute for +aggregate return in memory, if the caller is responsible to pop the hidden +pointer together with the rest of the arguments - @var{number} equal to +zero -, or if the callee is responsible to pop hidden pointer - @var{number} +equal to one. + +For i?86-netware, the caller pops the stack for the hidden arguments pointing +to aggregate return value. This differs from the default i386 ABI which assumes +that the callee pops the stack for hidden pointer. + +@item ms_hook_prologue +@cindex @code{ms_hook_prologue} attribute + +On 32 bit i[34567]86-*-* targets and 64 bit x86_64-*-* targets, you can use +this function attribute to make gcc generate the "hot-patching" function +prologue used in Win32 API functions in Microsoft Windows XP Service Pack 2 +and newer. + +@item naked +@cindex function without a prologue/epilogue code +Use this attribute on the ARM, AVR, MCORE, RX and SPU ports to indicate that +the specified function does not need prologue/epilogue sequences generated by +the compiler. It is up to the programmer to provide these sequences. The +only statements that can be safely included in naked functions are +@code{asm} statements that do not have operands. All other statements, +including declarations of local variables, @code{if} statements, and so +forth, should be avoided. Naked functions should be used to implement the +body of an assembly function, while allowing the compiler to construct +the requisite function declaration for the assembler. + +@item near +@cindex functions which do not handle memory bank switching on 68HC11/68HC12 +On 68HC11 and 68HC12 the @code{near} attribute causes the compiler to +use the normal calling convention based on @code{jsr} and @code{rts}. +This attribute can be used to cancel the effect of the @option{-mlong-calls} +option. + +On MeP targets this attribute causes the compiler to assume the called +function is close enough to use the normal calling convention, +overriding the @code{-mtf} command line option. + +@item nesting +@cindex Allow nesting in an interrupt handler on the Blackfin processor. +Use this attribute together with @code{interrupt_handler}, +@code{exception_handler} or @code{nmi_handler} to indicate that the function +entry code should enable nested interrupts or exceptions. + +@item nmi_handler +@cindex NMI handler functions on the Blackfin processor +Use this attribute on the Blackfin to indicate that the specified function +is an NMI handler. The compiler will generate function entry and +exit sequences suitable for use in an NMI handler when this +attribute is present. + +@item no_instrument_function +@cindex @code{no_instrument_function} function attribute +@opindex finstrument-functions +If @option{-finstrument-functions} is given, profiling function calls will +be generated at entry and exit of most user-compiled functions. +Functions with this attribute will not be so instrumented. + +@item no_split_stack +@cindex @code{no_split_stack} function attribute +@opindex fsplit-stack +If @option{-fsplit-stack} is given, functions will have a small +prologue which decides whether to split the stack. Functions with the +@code{no_split_stack} attribute will not have that prologue, and thus +may run with only a small amount of stack space available. + +@item noinline +@cindex @code{noinline} function attribute +This function attribute prevents a function from being considered for +inlining. +@c Don't enumerate the optimizations by name here; we try to be +@c future-compatible with this mechanism. +If the function does not have side-effects, there are optimizations +other than inlining that causes function calls to be optimized away, +although the function call is live. To keep such calls from being +optimized away, put +@smallexample +asm (""); +@end smallexample +(@pxref{Extended Asm}) in the called function, to serve as a special +side-effect. + +@item noclone +@cindex @code{noclone} function attribute +This function attribute prevents a function from being considered for +cloning - a mechanism which produces specialized copies of functions +and which is (currently) performed by interprocedural constant +propagation. + +@item nonnull (@var{arg-index}, @dots{}) +@cindex @code{nonnull} function attribute +The @code{nonnull} attribute specifies that some function parameters should +be non-null pointers. For instance, the declaration: + +@smallexample +extern void * +my_memcpy (void *dest, const void *src, size_t len) + __attribute__((nonnull (1, 2))); +@end smallexample + +@noindent +causes the compiler to check that, in calls to @code{my_memcpy}, +arguments @var{dest} and @var{src} are non-null. If the compiler +determines that a null pointer is passed in an argument slot marked +as non-null, and the @option{-Wnonnull} option is enabled, a warning +is issued. The compiler may also choose to make optimizations based +on the knowledge that certain function arguments will not be null. + +If no argument index list is given to the @code{nonnull} attribute, +all pointer arguments are marked as non-null. To illustrate, the +following declaration is equivalent to the previous example: + +@smallexample +extern void * +my_memcpy (void *dest, const void *src, size_t len) + __attribute__((nonnull)); +@end smallexample + +@item noreturn +@cindex @code{noreturn} function attribute +A few standard library functions, such as @code{abort} and @code{exit}, +cannot return. GCC knows this automatically. Some programs define +their own functions that never return. You can declare them +@code{noreturn} to tell the compiler this fact. For example, + +@smallexample +@group +void fatal () __attribute__ ((noreturn)); + +void +fatal (/* @r{@dots{}} */) +@{ + /* @r{@dots{}} */ /* @r{Print error message.} */ /* @r{@dots{}} */ + exit (1); +@} +@end group +@end smallexample + +The @code{noreturn} keyword tells the compiler to assume that +@code{fatal} cannot return. It can then optimize without regard to what +would happen if @code{fatal} ever did return. This makes slightly +better code. More importantly, it helps avoid spurious warnings of +uninitialized variables. + +The @code{noreturn} keyword does not affect the exceptional path when that +applies: a @code{noreturn}-marked function may still return to the caller +by throwing an exception or calling @code{longjmp}. + +Do not assume that registers saved by the calling function are +restored before calling the @code{noreturn} function. + +It does not make sense for a @code{noreturn} function to have a return +type other than @code{void}. + +The attribute @code{noreturn} is not implemented in GCC versions +earlier than 2.5. An alternative way to declare that a function does +not return, which works in the current version and in some older +versions, is as follows: + +@smallexample +typedef void voidfn (); + +volatile voidfn fatal; +@end smallexample + +This approach does not work in GNU C++. + +@item nothrow +@cindex @code{nothrow} function attribute +The @code{nothrow} attribute is used to inform the compiler that a +function cannot throw an exception. For example, most functions in +the standard C library can be guaranteed not to throw an exception +with the notable exceptions of @code{qsort} and @code{bsearch} that +take function pointer arguments. The @code{nothrow} attribute is not +implemented in GCC versions earlier than 3.3. + +@item optimize +@cindex @code{optimize} function attribute +The @code{optimize} attribute is used to specify that a function is to +be compiled with different optimization options than specified on the +command line. Arguments can either be numbers or strings. Numbers +are assumed to be an optimization level. Strings that begin with +@code{O} are assumed to be an optimization option, while other options +are assumed to be used with a @code{-f} prefix. You can also use the +@samp{#pragma GCC optimize} pragma to set the optimization options +that affect more than one function. +@xref{Function Specific Option Pragmas}, for details about the +@samp{#pragma GCC optimize} pragma. + +This can be used for instance to have frequently executed functions +compiled with more aggressive optimization options that produce faster +and larger code, while other functions can be called with less +aggressive options. + +@item OS_main/OS_task +@cindex @code{OS_main} AVR function attribute +@cindex @code{OS_task} AVR function attribute +On AVR, functions with the @code{OS_main} or @code{OS_task} attribute +do not save/restore any call-saved register in their prologue/epilogue. + +The @code{OS_main} attribute can be used when there @emph{is +guarantee} that interrupts are disabled at the time when the function +is entered. This will save resources when the stack pointer has to be +changed to set up a frame for local variables. + +The @code{OS_task} attribute can be used when there is @emph{no +guarantee} that interrupts are disabled at that time when the function +is entered like for, e@.g@. task functions in a multi-threading operating +system. In that case, changing the stack pointer register will be +guarded by save/clear/restore of the global interrupt enable flag. + +The differences to the @code{naked} function attrubute are: +@itemize @bullet +@item @code{naked} functions do not have a return instruction whereas +@code{OS_main} and @code{OS_task} functions will have a @code{RET} or +@code{RETI} return instruction. +@item @code{naked} functions do not set up a frame for local variables +or a frame pointer whereas @code{OS_main} and @code{OS_task} do this +as needed. +@end itemize + +@item pcs +@cindex @code{pcs} function attribute + +The @code{pcs} attribute can be used to control the calling convention +used for a function on ARM. The attribute takes an argument that specifies +the calling convention to use. + +When compiling using the AAPCS ABI (or a variant of that) then valid +values for the argument are @code{"aapcs"} and @code{"aapcs-vfp"}. In +order to use a variant other than @code{"aapcs"} then the compiler must +be permitted to use the appropriate co-processor registers (i.e., the +VFP registers must be available in order to use @code{"aapcs-vfp"}). +For example, + +@smallexample +/* Argument passed in r0, and result returned in r0+r1. */ +double f2d (float) __attribute__((pcs("aapcs"))); +@end smallexample + +Variadic functions always use the @code{"aapcs"} calling convention and +the compiler will reject attempts to specify an alternative. + +@item pure +@cindex @code{pure} function attribute +Many functions have no effects except the return value and their +return value depends only on the parameters and/or global variables. +Such a function can be subject +to common subexpression elimination and loop optimization just as an +arithmetic operator would be. These functions should be declared +with the attribute @code{pure}. For example, + +@smallexample +int square (int) __attribute__ ((pure)); +@end smallexample + +@noindent +says that the hypothetical function @code{square} is safe to call +fewer times than the program says. + +Some of common examples of pure functions are @code{strlen} or @code{memcmp}. +Interesting non-pure functions are functions with infinite loops or those +depending on volatile memory or other system resource, that may change between +two consecutive calls (such as @code{feof} in a multithreading environment). + +The attribute @code{pure} is not implemented in GCC versions earlier +than 2.96. + +@item hot +@cindex @code{hot} function attribute +The @code{hot} attribute is used to inform the compiler that a function is a +hot spot of the compiled program. The function is optimized more aggressively +and on many target it is placed into special subsection of the text section so +all hot functions appears close together improving locality. + +When profile feedback is available, via @option{-fprofile-use}, hot functions +are automatically detected and this attribute is ignored. + +The @code{hot} attribute is not implemented in GCC versions earlier +than 4.3. + +@item cold +@cindex @code{cold} function attribute +The @code{cold} attribute is used to inform the compiler that a function is +unlikely executed. The function is optimized for size rather than speed and on +many targets it is placed into special subsection of the text section so all +cold functions appears close together improving code locality of non-cold parts +of program. The paths leading to call of cold functions within code are marked +as unlikely by the branch prediction mechanism. It is thus useful to mark +functions used to handle unlikely conditions, such as @code{perror}, as cold to +improve optimization of hot functions that do call marked functions in rare +occasions. + +When profile feedback is available, via @option{-fprofile-use}, hot functions +are automatically detected and this attribute is ignored. + +The @code{cold} attribute is not implemented in GCC versions earlier than 4.3. + +@item regparm (@var{number}) +@cindex @code{regparm} attribute +@cindex functions that are passed arguments in registers on the 386 +On the Intel 386, the @code{regparm} attribute causes the compiler to +pass arguments number one to @var{number} if they are of integral type +in registers EAX, EDX, and ECX instead of on the stack. Functions that +take a variable number of arguments will continue to be passed all of their +arguments on the stack. + +Beware that on some ELF systems this attribute is unsuitable for +global functions in shared libraries with lazy binding (which is the +default). Lazy binding will send the first call via resolving code in +the loader, which might assume EAX, EDX and ECX can be clobbered, as +per the standard calling conventions. Solaris 8 is affected by this. +GNU systems with GLIBC 2.1 or higher, and FreeBSD, are believed to be +safe since the loaders there save EAX, EDX and ECX. (Lazy binding can be +disabled with the linker or the loader if desired, to avoid the +problem.) + +@item sseregparm +@cindex @code{sseregparm} attribute +On the Intel 386 with SSE support, the @code{sseregparm} attribute +causes the compiler to pass up to 3 floating point arguments in +SSE registers instead of on the stack. Functions that take a +variable number of arguments will continue to pass all of their +floating point arguments on the stack. + +@item force_align_arg_pointer +@cindex @code{force_align_arg_pointer} attribute +On the Intel x86, the @code{force_align_arg_pointer} attribute may be +applied to individual function definitions, generating an alternate +prologue and epilogue that realigns the runtime stack if necessary. +This supports mixing legacy codes that run with a 4-byte aligned stack +with modern codes that keep a 16-byte stack for SSE compatibility. + +@item resbank +@cindex @code{resbank} attribute +On the SH2A target, this attribute enables the high-speed register +saving and restoration using a register bank for @code{interrupt_handler} +routines. Saving to the bank is performed automatically after the CPU +accepts an interrupt that uses a register bank. + +The nineteen 32-bit registers comprising general register R0 to R14, +control register GBR, and system registers MACH, MACL, and PR and the +vector table address offset are saved into a register bank. Register +banks are stacked in first-in last-out (FILO) sequence. Restoration +from the bank is executed by issuing a RESBANK instruction. + +@item returns_twice +@cindex @code{returns_twice} attribute +The @code{returns_twice} attribute tells the compiler that a function may +return more than one time. The compiler will ensure that all registers +are dead before calling such a function and will emit a warning about +the variables that may be clobbered after the second return from the +function. Examples of such functions are @code{setjmp} and @code{vfork}. +The @code{longjmp}-like counterpart of such function, if any, might need +to be marked with the @code{noreturn} attribute. + +@item saveall +@cindex save all registers on the Blackfin, H8/300, H8/300H, and H8S +Use this attribute on the Blackfin, H8/300, H8/300H, and H8S to indicate that +all registers except the stack pointer should be saved in the prologue +regardless of whether they are used or not. + +@item save_volatiles +@cindex save volatile registers on the MicroBlaze +Use this attribute on the MicroBlaze to indicate that the function is +an interrupt handler. All volatile registers (in addition to non-volatile +registers) will be saved in the function prologue. If the function is a leaf +function, only volatiles used by the function are saved. A normal function +return is generated instead of a return from interrupt. + +@item section ("@var{section-name}") +@cindex @code{section} function attribute +Normally, the compiler places the code it generates in the @code{text} section. +Sometimes, however, you need additional sections, or you need certain +particular functions to appear in special sections. The @code{section} +attribute specifies that a function lives in a particular section. +For example, the declaration: + +@smallexample +extern void foobar (void) __attribute__ ((section ("bar"))); +@end smallexample + +@noindent +puts the function @code{foobar} in the @code{bar} section. + +Some file formats do not support arbitrary sections so the @code{section} +attribute is not available on all platforms. +If you need to map the entire contents of a module to a particular +section, consider using the facilities of the linker instead. + +@item sentinel +@cindex @code{sentinel} function attribute +This function attribute ensures that a parameter in a function call is +an explicit @code{NULL}. The attribute is only valid on variadic +functions. By default, the sentinel is located at position zero, the +last parameter of the function call. If an optional integer position +argument P is supplied to the attribute, the sentinel must be located at +position P counting backwards from the end of the argument list. + +@smallexample +__attribute__ ((sentinel)) +is equivalent to +__attribute__ ((sentinel(0))) +@end smallexample + +The attribute is automatically set with a position of 0 for the built-in +functions @code{execl} and @code{execlp}. The built-in function +@code{execle} has the attribute set with a position of 1. + +A valid @code{NULL} in this context is defined as zero with any pointer +type. If your system defines the @code{NULL} macro with an integer type +then you need to add an explicit cast. GCC replaces @code{stddef.h} +with a copy that redefines NULL appropriately. + +The warnings for missing or incorrect sentinels are enabled with +@option{-Wformat}. + +@item short_call +See long_call/short_call. + +@item shortcall +See longcall/shortcall. + +@item signal +@cindex signal handler functions on the AVR processors +Use this attribute on the AVR to indicate that the specified +function is a signal handler. The compiler will generate function +entry and exit sequences suitable for use in a signal handler when this +attribute is present. Interrupts will be disabled inside the function. + +@item sp_switch +Use this attribute on the SH to indicate an @code{interrupt_handler} +function should switch to an alternate stack. It expects a string +argument that names a global variable holding the address of the +alternate stack. + +@smallexample +void *alt_stack; +void f () __attribute__ ((interrupt_handler, + sp_switch ("alt_stack"))); +@end smallexample + +@item stdcall +@cindex functions that pop the argument stack on the 386 +On the Intel 386, the @code{stdcall} attribute causes the compiler to +assume that the called function will pop off the stack space used to +pass arguments, unless it takes a variable number of arguments. + +@item syscall_linkage +@cindex @code{syscall_linkage} attribute +This attribute is used to modify the IA64 calling convention by marking +all input registers as live at all function exits. This makes it possible +to restart a system call after an interrupt without having to save/restore +the input registers. This also prevents kernel data from leaking into +application code. + +@item target +@cindex @code{target} function attribute +The @code{target} attribute is used to specify that a function is to +be compiled with different target options than specified on the +command line. This can be used for instance to have functions +compiled with a different ISA (instruction set architecture) than the +default. You can also use the @samp{#pragma GCC target} pragma to set +more than one function to be compiled with specific target options. +@xref{Function Specific Option Pragmas}, for details about the +@samp{#pragma GCC target} pragma. + +For instance on a 386, you could compile one function with +@code{target("sse4.1,arch=core2")} and another with +@code{target("sse4a,arch=amdfam10")} that would be equivalent to +compiling the first function with @option{-msse4.1} and +@option{-march=core2} options, and the second function with +@option{-msse4a} and @option{-march=amdfam10} options. It is up to the +user to make sure that a function is only invoked on a machine that +supports the particular ISA it was compiled for (for example by using +@code{cpuid} on 386 to determine what feature bits and architecture +family are used). + +@smallexample +int core2_func (void) __attribute__ ((__target__ ("arch=core2"))); +int sse3_func (void) __attribute__ ((__target__ ("sse3"))); +@end smallexample + +On the 386, the following options are allowed: + +@table @samp +@item abm +@itemx no-abm +@cindex @code{target("abm")} attribute +Enable/disable the generation of the advanced bit instructions. + +@item aes +@itemx no-aes +@cindex @code{target("aes")} attribute +Enable/disable the generation of the AES instructions. + +@item mmx +@itemx no-mmx +@cindex @code{target("mmx")} attribute +Enable/disable the generation of the MMX instructions. + +@item pclmul +@itemx no-pclmul +@cindex @code{target("pclmul")} attribute +Enable/disable the generation of the PCLMUL instructions. + +@item popcnt +@itemx no-popcnt +@cindex @code{target("popcnt")} attribute +Enable/disable the generation of the POPCNT instruction. + +@item sse +@itemx no-sse +@cindex @code{target("sse")} attribute +Enable/disable the generation of the SSE instructions. + +@item sse2 +@itemx no-sse2 +@cindex @code{target("sse2")} attribute +Enable/disable the generation of the SSE2 instructions. + +@item sse3 +@itemx no-sse3 +@cindex @code{target("sse3")} attribute +Enable/disable the generation of the SSE3 instructions. + +@item sse4 +@itemx no-sse4 +@cindex @code{target("sse4")} attribute +Enable/disable the generation of the SSE4 instructions (both SSE4.1 +and SSE4.2). + +@item sse4.1 +@itemx no-sse4.1 +@cindex @code{target("sse4.1")} attribute +Enable/disable the generation of the sse4.1 instructions. + +@item sse4.2 +@itemx no-sse4.2 +@cindex @code{target("sse4.2")} attribute +Enable/disable the generation of the sse4.2 instructions. + +@item sse4a +@itemx no-sse4a +@cindex @code{target("sse4a")} attribute +Enable/disable the generation of the SSE4A instructions. + +@item fma4 +@itemx no-fma4 +@cindex @code{target("fma4")} attribute +Enable/disable the generation of the FMA4 instructions. + +@item xop +@itemx no-xop +@cindex @code{target("xop")} attribute +Enable/disable the generation of the XOP instructions. + +@item lwp +@itemx no-lwp +@cindex @code{target("lwp")} attribute +Enable/disable the generation of the LWP instructions. + +@item ssse3 +@itemx no-ssse3 +@cindex @code{target("ssse3")} attribute +Enable/disable the generation of the SSSE3 instructions. + +@item cld +@itemx no-cld +@cindex @code{target("cld")} attribute +Enable/disable the generation of the CLD before string moves. + +@item fancy-math-387 +@itemx no-fancy-math-387 +@cindex @code{target("fancy-math-387")} attribute +Enable/disable the generation of the @code{sin}, @code{cos}, and +@code{sqrt} instructions on the 387 floating point unit. + +@item fused-madd +@itemx no-fused-madd +@cindex @code{target("fused-madd")} attribute +Enable/disable the generation of the fused multiply/add instructions. + +@item ieee-fp +@itemx no-ieee-fp +@cindex @code{target("ieee-fp")} attribute +Enable/disable the generation of floating point that depends on IEEE arithmetic. + +@item inline-all-stringops +@itemx no-inline-all-stringops +@cindex @code{target("inline-all-stringops")} attribute +Enable/disable inlining of string operations. + +@item inline-stringops-dynamically +@itemx no-inline-stringops-dynamically +@cindex @code{target("inline-stringops-dynamically")} attribute +Enable/disable the generation of the inline code to do small string +operations and calling the library routines for large operations. + +@item align-stringops +@itemx no-align-stringops +@cindex @code{target("align-stringops")} attribute +Do/do not align destination of inlined string operations. + +@item recip +@itemx no-recip +@cindex @code{target("recip")} attribute +Enable/disable the generation of RCPSS, RCPPS, RSQRTSS and RSQRTPS +instructions followed an additional Newton-Raphson step instead of +doing a floating point division. + +@item arch=@var{ARCH} +@cindex @code{target("arch=@var{ARCH}")} attribute +Specify the architecture to generate code for in compiling the function. + +@item tune=@var{TUNE} +@cindex @code{target("tune=@var{TUNE}")} attribute +Specify the architecture to tune for in compiling the function. + +@item fpmath=@var{FPMATH} +@cindex @code{target("fpmath=@var{FPMATH}")} attribute +Specify which floating point unit to use. The +@code{target("fpmath=sse,387")} option must be specified as +@code{target("fpmath=sse+387")} because the comma would separate +different options. +@end table + +On the PowerPC, the following options are allowed: + +@table @samp +@item altivec +@itemx no-altivec +@cindex @code{target("altivec")} attribute +Generate code that uses (does not use) AltiVec instructions. In +32-bit code, you cannot enable Altivec instructions unless +@option{-mabi=altivec} was used on the command line. + +@item cmpb +@itemx no-cmpb +@cindex @code{target("cmpb")} attribute +Generate code that uses (does not use) the compare bytes instruction +implemented on the POWER6 processor and other processors that support +the PowerPC V2.05 architecture. + +@item dlmzb +@itemx no-dlmzb +@cindex @code{target("dlmzb")} attribute +Generate code that uses (does not use) the string-search @samp{dlmzb} +instruction on the IBM 405, 440, 464 and 476 processors. This instruction is +generated by default when targetting those processors. + +@item fprnd +@itemx no-fprnd +@cindex @code{target("fprnd")} attribute +Generate code that uses (does not use) the FP round to integer +instructions implemented on the POWER5+ processor and other processors +that support the PowerPC V2.03 architecture. + +@item hard-dfp +@itemx no-hard-dfp +@cindex @code{target("hard-dfp")} attribute +Generate code that uses (does not use) the decimal floating point +instructions implemented on some POWER processors. + +@item isel +@itemx no-isel +@cindex @code{target("isel")} attribute +Generate code that uses (does not use) ISEL instruction. + +@item mfcrf +@itemx no-mfcrf +@cindex @code{target("mfcrf")} attribute +Generate code that uses (does not use) the move from condition +register field instruction implemented on the POWER4 processor and +other processors that support the PowerPC V2.01 architecture. + +@item mfpgpr +@itemx no-mfpgpr +@cindex @code{target("mfpgpr")} attribute +Generate code that uses (does not use) the FP move to/from general +purpose register instructions implemented on the POWER6X processor and +other processors that support the extended PowerPC V2.05 architecture. + +@item mulhw +@itemx no-mulhw +@cindex @code{target("mulhw")} attribute +Generate code that uses (does not use) the half-word multiply and +multiply-accumulate instructions on the IBM 405, 440, 464 and 476 processors. +These instructions are generated by default when targetting those +processors. + +@item multiple +@itemx no-multiple +@cindex @code{target("multiple")} attribute +Generate code that uses (does not use) the load multiple word +instructions and the store multiple word instructions. + +@item update +@itemx no-update +@cindex @code{target("update")} attribute +Generate code that uses (does not use) the load or store instructions +that update the base register to the address of the calculated memory +location. + +@item popcntb +@itemx no-popcntb +@cindex @code{target("popcntb")} attribute +Generate code that uses (does not use) the popcount and double +precision FP reciprocal estimate instruction implemented on the POWER5 +processor and other processors that support the PowerPC V2.02 +architecture. + +@item popcntd +@itemx no-popcntd +@cindex @code{target("popcntd")} attribute +Generate code that uses (does not use) the popcount instruction +implemented on the POWER7 processor and other processors that support +the PowerPC V2.06 architecture. + +@item powerpc-gfxopt +@itemx no-powerpc-gfxopt +@cindex @code{target("powerpc-gfxopt")} attribute +Generate code that uses (does not use) the optional PowerPC +architecture instructions in the Graphics group, including +floating-point select. + +@item powerpc-gpopt +@itemx no-powerpc-gpopt +@cindex @code{target("powerpc-gpopt")} attribute +Generate code that uses (does not use) the optional PowerPC +architecture instructions in the General Purpose group, including +floating-point square root. + +@item recip-precision +@itemx no-recip-precision +@cindex @code{target("recip-precision")} attribute +Assume (do not assume) that the reciprocal estimate instructions +provide higher precision estimates than is mandated by the powerpc +ABI. + +@item string +@itemx no-string +@cindex @code{target("string")} attribute +Generate code that uses (does not use) the load string instructions +and the store string word instructions to save multiple registers and +do small block moves. + +@item vsx +@itemx no-vsx +@cindex @code{target("vsx")} attribute +Generate code that uses (does not use) vector/scalar (VSX) +instructions, and also enable the use of built-in functions that allow +more direct access to the VSX instruction set. In 32-bit code, you +cannot enable VSX or Altivec instructions unless +@option{-mabi=altivec} was used on the command line. + +@item friz +@itemx no-friz +@cindex @code{target("friz")} attribute +Generate (do not generate) the @code{friz} instruction when the +@option{-funsafe-math-optimizations} option is used to optimize +rounding a floating point value to 64-bit integer and back to floating +point. The @code{friz} instruction does not return the same value if +the floating point number is too large to fit in an integer. + +@item avoid-indexed-addresses +@itemx no-avoid-indexed-addresses +@cindex @code{target("avoid-indexed-addresses")} attribute +Generate code that tries to avoid (not avoid) the use of indexed load +or store instructions. + +@item paired +@itemx no-paired +@cindex @code{target("paired")} attribute +Generate code that uses (does not use) the generation of PAIRED simd +instructions. + +@item longcall +@itemx no-longcall +@cindex @code{target("longcall")} attribute +Generate code that assumes (does not assume) that all calls are far +away so that a longer more expensive calling sequence is required. + +@item cpu=@var{CPU} +@cindex @code{target("cpu=@var{CPU}")} attribute +Specify the architecture to generate code for when compiling the +function. If you select the @code{"target("cpu=power7)"} attribute when +generating 32-bit code, VSX and Altivec instructions are not generated +unless you use the @option{-mabi=altivec} option on the command line. + +@item tune=@var{TUNE} +@cindex @code{target("tune=@var{TUNE}")} attribute +Specify the architecture to tune for when compiling the function. If +you do not specify the @code{target("tune=@var{TUNE}")} attribute and +you do specify the @code{target("cpu=@var{CPU}")} attribute, +compilation will tune for the @var{CPU} architecture, and not the +default tuning specified on the command line. +@end table + +On the 386/x86_64 and PowerPC backends, you can use either multiple +strings to specify multiple options, or you can separate the option +with a comma (@code{,}). + +On the 386/x86_64 and PowerPC backends, the inliner will not inline a +function that has different target options than the caller, unless the +callee has a subset of the target options of the caller. For example +a function declared with @code{target("sse3")} can inline a function +with @code{target("sse2")}, since @code{-msse3} implies @code{-msse2}. + +The @code{target} attribute is not implemented in GCC versions earlier +than 4.4 for the i386/x86_64 and 4.6 for the PowerPC backends. It is +not currently implemented for other backends. + +@item tiny_data +@cindex tiny data section on the H8/300H and H8S +Use this attribute on the H8/300H and H8S to indicate that the specified +variable should be placed into the tiny data section. +The compiler will generate more efficient code for loads and stores +on data in the tiny data section. Note the tiny data area is limited to +slightly under 32kbytes of data. + +@item trap_exit +Use this attribute on the SH for an @code{interrupt_handler} to return using +@code{trapa} instead of @code{rte}. This attribute expects an integer +argument specifying the trap number to be used. + +@item unused +@cindex @code{unused} attribute. +This attribute, attached to a function, means that the function is meant +to be possibly unused. GCC will not produce a warning for this +function. + +@item used +@cindex @code{used} attribute. +This attribute, attached to a function, means that code must be emitted +for the function even if it appears that the function is not referenced. +This is useful, for example, when the function is referenced only in +inline assembly. + +@item version_id +@cindex @code{version_id} attribute +This IA64 HP-UX attribute, attached to a global variable or function, renames a +symbol to contain a version string, thus allowing for function level +versioning. HP-UX system header files may use version level functioning +for some system calls. + +@smallexample +extern int foo () __attribute__((version_id ("20040821"))); +@end smallexample + +Calls to @var{foo} will be mapped to calls to @var{foo@{20040821@}}. + +@item visibility ("@var{visibility_type}") +@cindex @code{visibility} attribute +This attribute affects the linkage of the declaration to which it is attached. +There are four supported @var{visibility_type} values: default, +hidden, protected or internal visibility. + +@smallexample +void __attribute__ ((visibility ("protected"))) +f () @{ /* @r{Do something.} */; @} +int i __attribute__ ((visibility ("hidden"))); +@end smallexample + +The possible values of @var{visibility_type} correspond to the +visibility settings in the ELF gABI. + +@table @dfn +@c keep this list of visibilities in alphabetical order. + +@item default +Default visibility is the normal case for the object file format. +This value is available for the visibility attribute to override other +options that may change the assumed visibility of entities. + +On ELF, default visibility means that the declaration is visible to other +modules and, in shared libraries, means that the declared entity may be +overridden. + +On Darwin, default visibility means that the declaration is visible to +other modules. + +Default visibility corresponds to ``external linkage'' in the language. + +@item hidden +Hidden visibility indicates that the entity declared will have a new +form of linkage, which we'll call ``hidden linkage''. Two +declarations of an object with hidden linkage refer to the same object +if they are in the same shared object. + +@item internal +Internal visibility is like hidden visibility, but with additional +processor specific semantics. Unless otherwise specified by the +psABI, GCC defines internal visibility to mean that a function is +@emph{never} called from another module. Compare this with hidden +functions which, while they cannot be referenced directly by other +modules, can be referenced indirectly via function pointers. By +indicating that a function cannot be called from outside the module, +GCC may for instance omit the load of a PIC register since it is known +that the calling function loaded the correct value. + +@item protected +Protected visibility is like default visibility except that it +indicates that references within the defining module will bind to the +definition in that module. That is, the declared entity cannot be +overridden by another module. + +@end table + +All visibilities are supported on many, but not all, ELF targets +(supported when the assembler supports the @samp{.visibility} +pseudo-op). Default visibility is supported everywhere. Hidden +visibility is supported on Darwin targets. + +The visibility attribute should be applied only to declarations which +would otherwise have external linkage. The attribute should be applied +consistently, so that the same entity should not be declared with +different settings of the attribute. + +In C++, the visibility attribute applies to types as well as functions +and objects, because in C++ types have linkage. A class must not have +greater visibility than its non-static data member types and bases, +and class members default to the visibility of their class. Also, a +declaration without explicit visibility is limited to the visibility +of its type. + +In C++, you can mark member functions and static member variables of a +class with the visibility attribute. This is useful if you know a +particular method or static member variable should only be used from +one shared object; then you can mark it hidden while the rest of the +class has default visibility. Care must be taken to avoid breaking +the One Definition Rule; for example, it is usually not useful to mark +an inline method as hidden without marking the whole class as hidden. + +A C++ namespace declaration can also have the visibility attribute. +This attribute applies only to the particular namespace body, not to +other definitions of the same namespace; it is equivalent to using +@samp{#pragma GCC visibility} before and after the namespace +definition (@pxref{Visibility Pragmas}). + +In C++, if a template argument has limited visibility, this +restriction is implicitly propagated to the template instantiation. +Otherwise, template instantiations and specializations default to the +visibility of their template. + +If both the template and enclosing class have explicit visibility, the +visibility from the template is used. + +@item vliw +@cindex @code{vliw} attribute +On MeP, the @code{vliw} attribute tells the compiler to emit +instructions in VLIW mode instead of core mode. Note that this +attribute is not allowed unless a VLIW coprocessor has been configured +and enabled through command line options. + +@item warn_unused_result +@cindex @code{warn_unused_result} attribute +The @code{warn_unused_result} attribute causes a warning to be emitted +if a caller of the function with this attribute does not use its +return value. This is useful for functions where not checking +the result is either a security problem or always a bug, such as +@code{realloc}. + +@smallexample +int fn () __attribute__ ((warn_unused_result)); +int foo () +@{ + if (fn () < 0) return -1; + fn (); + return 0; +@} +@end smallexample + +results in warning on line 5. + +@item weak +@cindex @code{weak} attribute +The @code{weak} attribute causes the declaration to be emitted as a weak +symbol rather than a global. This is primarily useful in defining +library functions which can be overridden in user code, though it can +also be used with non-function declarations. Weak symbols are supported +for ELF targets, and also for a.out targets when using the GNU assembler +and linker. + +@item weakref +@itemx weakref ("@var{target}") +@cindex @code{weakref} attribute +The @code{weakref} attribute marks a declaration as a weak reference. +Without arguments, it should be accompanied by an @code{alias} attribute +naming the target symbol. Optionally, the @var{target} may be given as +an argument to @code{weakref} itself. In either case, @code{weakref} +implicitly marks the declaration as @code{weak}. Without a +@var{target}, given as an argument to @code{weakref} or to @code{alias}, +@code{weakref} is equivalent to @code{weak}. + +@smallexample +static int x() __attribute__ ((weakref ("y"))); +/* is equivalent to... */ +static int x() __attribute__ ((weak, weakref, alias ("y"))); +/* and to... */ +static int x() __attribute__ ((weakref)); +static int x() __attribute__ ((alias ("y"))); +@end smallexample + +A weak reference is an alias that does not by itself require a +definition to be given for the target symbol. If the target symbol is +only referenced through weak references, then it becomes a @code{weak} +undefined symbol. If it is directly referenced, however, then such +strong references prevail, and a definition will be required for the +symbol, not necessarily in the same translation unit. + +The effect is equivalent to moving all references to the alias to a +separate translation unit, renaming the alias to the aliased symbol, +declaring it as weak, compiling the two separate translation units and +performing a reloadable link on them. + +At present, a declaration to which @code{weakref} is attached can +only be @code{static}. + +@end table + +You can specify multiple attributes in a declaration by separating them +by commas within the double parentheses or by immediately following an +attribute declaration with another attribute declaration. + +@cindex @code{#pragma}, reason for not using +@cindex pragma, reason for not using +Some people object to the @code{__attribute__} feature, suggesting that +ISO C's @code{#pragma} should be used instead. At the time +@code{__attribute__} was designed, there were two reasons for not doing +this. + +@enumerate +@item +It is impossible to generate @code{#pragma} commands from a macro. + +@item +There is no telling what the same @code{#pragma} might mean in another +compiler. +@end enumerate + +These two reasons applied to almost any application that might have been +proposed for @code{#pragma}. It was basically a mistake to use +@code{#pragma} for @emph{anything}. + +The ISO C99 standard includes @code{_Pragma}, which now allows pragmas +to be generated from macros. In addition, a @code{#pragma GCC} +namespace is now in use for GCC-specific pragmas. However, it has been +found convenient to use @code{__attribute__} to achieve a natural +attachment of attributes to their corresponding declarations, whereas +@code{#pragma GCC} is of use for constructs that do not naturally form +part of the grammar. @xref{Other Directives,,Miscellaneous +Preprocessing Directives, cpp, The GNU C Preprocessor}. + +@node Attribute Syntax +@section Attribute Syntax +@cindex attribute syntax + +This section describes the syntax with which @code{__attribute__} may be +used, and the constructs to which attribute specifiers bind, for the C +language. Some details may vary for C++ and Objective-C@. Because of +infelicities in the grammar for attributes, some forms described here +may not be successfully parsed in all cases. + +There are some problems with the semantics of attributes in C++. For +example, there are no manglings for attributes, although they may affect +code generation, so problems may arise when attributed types are used in +conjunction with templates or overloading. Similarly, @code{typeid} +does not distinguish between types with different attributes. Support +for attributes in C++ may be restricted in future to attributes on +declarations only, but not on nested declarators. + +@xref{Function Attributes}, for details of the semantics of attributes +applying to functions. @xref{Variable Attributes}, for details of the +semantics of attributes applying to variables. @xref{Type Attributes}, +for details of the semantics of attributes applying to structure, union +and enumerated types. + +An @dfn{attribute specifier} is of the form +@code{__attribute__ ((@var{attribute-list}))}. An @dfn{attribute list} +is a possibly empty comma-separated sequence of @dfn{attributes}, where +each attribute is one of the following: + +@itemize @bullet +@item +Empty. Empty attributes are ignored. + +@item +A word (which may be an identifier such as @code{unused}, or a reserved +word such as @code{const}). + +@item +A word, followed by, in parentheses, parameters for the attribute. +These parameters take one of the following forms: + +@itemize @bullet +@item +An identifier. For example, @code{mode} attributes use this form. + +@item +An identifier followed by a comma and a non-empty comma-separated list +of expressions. For example, @code{format} attributes use this form. + +@item +A possibly empty comma-separated list of expressions. For example, +@code{format_arg} attributes use this form with the list being a single +integer constant expression, and @code{alias} attributes use this form +with the list being a single string constant. +@end itemize +@end itemize + +An @dfn{attribute specifier list} is a sequence of one or more attribute +specifiers, not separated by any other tokens. + +In GNU C, an attribute specifier list may appear after the colon following a +label, other than a @code{case} or @code{default} label. The only +attribute it makes sense to use after a label is @code{unused}. This +feature is intended for code generated by programs which contains labels +that may be unused but which is compiled with @option{-Wall}. It would +not normally be appropriate to use in it human-written code, though it +could be useful in cases where the code that jumps to the label is +contained within an @code{#ifdef} conditional. GNU C++ only permits +attributes on labels if the attribute specifier is immediately +followed by a semicolon (i.e., the label applies to an empty +statement). If the semicolon is missing, C++ label attributes are +ambiguous, as it is permissible for a declaration, which could begin +with an attribute list, to be labelled in C++. Declarations cannot be +labelled in C90 or C99, so the ambiguity does not arise there. + +An attribute specifier list may appear as part of a @code{struct}, +@code{union} or @code{enum} specifier. It may go either immediately +after the @code{struct}, @code{union} or @code{enum} keyword, or after +the closing brace. The former syntax is preferred. +Where attribute specifiers follow the closing brace, they are considered +to relate to the structure, union or enumerated type defined, not to any +enclosing declaration the type specifier appears in, and the type +defined is not complete until after the attribute specifiers. +@c Otherwise, there would be the following problems: a shift/reduce +@c conflict between attributes binding the struct/union/enum and +@c binding to the list of specifiers/qualifiers; and "aligned" +@c attributes could use sizeof for the structure, but the size could be +@c changed later by "packed" attributes. + +Otherwise, an attribute specifier appears as part of a declaration, +counting declarations of unnamed parameters and type names, and relates +to that declaration (which may be nested in another declaration, for +example in the case of a parameter declaration), or to a particular declarator +within a declaration. Where an +attribute specifier is applied to a parameter declared as a function or +an array, it should apply to the function or array rather than the +pointer to which the parameter is implicitly converted, but this is not +yet correctly implemented. + +Any list of specifiers and qualifiers at the start of a declaration may +contain attribute specifiers, whether or not such a list may in that +context contain storage class specifiers. (Some attributes, however, +are essentially in the nature of storage class specifiers, and only make +sense where storage class specifiers may be used; for example, +@code{section}.) There is one necessary limitation to this syntax: the +first old-style parameter declaration in a function definition cannot +begin with an attribute specifier, because such an attribute applies to +the function instead by syntax described below (which, however, is not +yet implemented in this case). In some other cases, attribute +specifiers are permitted by this grammar but not yet supported by the +compiler. All attribute specifiers in this place relate to the +declaration as a whole. In the obsolescent usage where a type of +@code{int} is implied by the absence of type specifiers, such a list of +specifiers and qualifiers may be an attribute specifier list with no +other specifiers or qualifiers. + +At present, the first parameter in a function prototype must have some +type specifier which is not an attribute specifier; this resolves an +ambiguity in the interpretation of @code{void f(int +(__attribute__((foo)) x))}, but is subject to change. At present, if +the parentheses of a function declarator contain only attributes then +those attributes are ignored, rather than yielding an error or warning +or implying a single parameter of type int, but this is subject to +change. + +An attribute specifier list may appear immediately before a declarator +(other than the first) in a comma-separated list of declarators in a +declaration of more than one identifier using a single list of +specifiers and qualifiers. Such attribute specifiers apply +only to the identifier before whose declarator they appear. For +example, in + +@smallexample +__attribute__((noreturn)) void d0 (void), + __attribute__((format(printf, 1, 2))) d1 (const char *, ...), + d2 (void) +@end smallexample + +@noindent +the @code{noreturn} attribute applies to all the functions +declared; the @code{format} attribute only applies to @code{d1}. + +An attribute specifier list may appear immediately before the comma, +@code{=} or semicolon terminating the declaration of an identifier other +than a function definition. Such attribute specifiers apply +to the declared object or function. Where an +assembler name for an object or function is specified (@pxref{Asm +Labels}), the attribute must follow the @code{asm} +specification. + +An attribute specifier list may, in future, be permitted to appear after +the declarator in a function definition (before any old-style parameter +declarations or the function body). + +Attribute specifiers may be mixed with type qualifiers appearing inside +the @code{[]} of a parameter array declarator, in the C99 construct by +which such qualifiers are applied to the pointer to which the array is +implicitly converted. Such attribute specifiers apply to the pointer, +not to the array, but at present this is not implemented and they are +ignored. + +An attribute specifier list may appear at the start of a nested +declarator. At present, there are some limitations in this usage: the +attributes correctly apply to the declarator, but for most individual +attributes the semantics this implies are not implemented. +When attribute specifiers follow the @code{*} of a pointer +declarator, they may be mixed with any type qualifiers present. +The following describes the formal semantics of this syntax. It will make the +most sense if you are familiar with the formal specification of +declarators in the ISO C standard. + +Consider (as in C99 subclause 6.7.5 paragraph 4) a declaration @code{T +D1}, where @code{T} contains declaration specifiers that specify a type +@var{Type} (such as @code{int}) and @code{D1} is a declarator that +contains an identifier @var{ident}. The type specified for @var{ident} +for derived declarators whose type does not include an attribute +specifier is as in the ISO C standard. + +If @code{D1} has the form @code{( @var{attribute-specifier-list} D )}, +and the declaration @code{T D} specifies the type +``@var{derived-declarator-type-list} @var{Type}'' for @var{ident}, then +@code{T D1} specifies the type ``@var{derived-declarator-type-list} +@var{attribute-specifier-list} @var{Type}'' for @var{ident}. + +If @code{D1} has the form @code{* +@var{type-qualifier-and-attribute-specifier-list} D}, and the +declaration @code{T D} specifies the type +``@var{derived-declarator-type-list} @var{Type}'' for @var{ident}, then +@code{T D1} specifies the type ``@var{derived-declarator-type-list} +@var{type-qualifier-and-attribute-specifier-list} pointer to @var{Type}'' for +@var{ident}. + +For example, + +@smallexample +void (__attribute__((noreturn)) ****f) (void); +@end smallexample + +@noindent +specifies the type ``pointer to pointer to pointer to pointer to +non-returning function returning @code{void}''. As another example, + +@smallexample +char *__attribute__((aligned(8))) *f; +@end smallexample + +@noindent +specifies the type ``pointer to 8-byte-aligned pointer to @code{char}''. +Note again that this does not work with most attributes; for example, +the usage of @samp{aligned} and @samp{noreturn} attributes given above +is not yet supported. + +For compatibility with existing code written for compiler versions that +did not implement attributes on nested declarators, some laxity is +allowed in the placing of attributes. If an attribute that only applies +to types is applied to a declaration, it will be treated as applying to +the type of that declaration. If an attribute that only applies to +declarations is applied to the type of a declaration, it will be treated +as applying to that declaration; and, for compatibility with code +placing the attributes immediately before the identifier declared, such +an attribute applied to a function return type will be treated as +applying to the function type, and such an attribute applied to an array +element type will be treated as applying to the array type. If an +attribute that only applies to function types is applied to a +pointer-to-function type, it will be treated as applying to the pointer +target type; if such an attribute is applied to a function return type +that is not a pointer-to-function type, it will be treated as applying +to the function type. + +@node Function Prototypes +@section Prototypes and Old-Style Function Definitions +@cindex function prototype declarations +@cindex old-style function definitions +@cindex promotion of formal parameters + +GNU C extends ISO C to allow a function prototype to override a later +old-style non-prototype definition. Consider the following example: + +@smallexample +/* @r{Use prototypes unless the compiler is old-fashioned.} */ +#ifdef __STDC__ +#define P(x) x +#else +#define P(x) () +#endif + +/* @r{Prototype function declaration.} */ +int isroot P((uid_t)); + +/* @r{Old-style function definition.} */ +int +isroot (x) /* @r{??? lossage here ???} */ + uid_t x; +@{ + return x == 0; +@} +@end smallexample + +Suppose the type @code{uid_t} happens to be @code{short}. ISO C does +not allow this example, because subword arguments in old-style +non-prototype definitions are promoted. Therefore in this example the +function definition's argument is really an @code{int}, which does not +match the prototype argument type of @code{short}. + +This restriction of ISO C makes it hard to write code that is portable +to traditional C compilers, because the programmer does not know +whether the @code{uid_t} type is @code{short}, @code{int}, or +@code{long}. Therefore, in cases like these GNU C allows a prototype +to override a later old-style definition. More precisely, in GNU C, a +function prototype argument type overrides the argument type specified +by a later old-style definition if the former type is the same as the +latter type before promotion. Thus in GNU C the above example is +equivalent to the following: + +@smallexample +int isroot (uid_t); + +int +isroot (uid_t x) +@{ + return x == 0; +@} +@end smallexample + +@noindent +GNU C++ does not support old-style function definitions, so this +extension is irrelevant. + +@node C++ Comments +@section C++ Style Comments +@cindex @code{//} +@cindex C++ comments +@cindex comments, C++ style + +In GNU C, you may use C++ style comments, which start with @samp{//} and +continue until the end of the line. Many other C implementations allow +such comments, and they are included in the 1999 C standard. However, +C++ style comments are not recognized if you specify an @option{-std} +option specifying a version of ISO C before C99, or @option{-ansi} +(equivalent to @option{-std=c90}). + +@node Dollar Signs +@section Dollar Signs in Identifier Names +@cindex $ +@cindex dollar signs in identifier names +@cindex identifier names, dollar signs in + +In GNU C, you may normally use dollar signs in identifier names. +This is because many traditional C implementations allow such identifiers. +However, dollar signs in identifiers are not supported on a few target +machines, typically because the target assembler does not allow them. + +@node Character Escapes +@section The Character @key{ESC} in Constants + +You can use the sequence @samp{\e} in a string or character constant to +stand for the ASCII character @key{ESC}. + +@node Variable Attributes +@section Specifying Attributes of Variables +@cindex attribute of variables +@cindex variable attributes + +The keyword @code{__attribute__} allows you to specify special +attributes of variables or structure fields. This keyword is followed +by an attribute specification inside double parentheses. Some +attributes are currently defined generically for variables. +Other attributes are defined for variables on particular target +systems. Other attributes are available for functions +(@pxref{Function Attributes}) and for types (@pxref{Type Attributes}). +Other front ends might define more attributes +(@pxref{C++ Extensions,,Extensions to the C++ Language}). + +You may also specify attributes with @samp{__} preceding and following +each keyword. This allows you to use them in header files without +being concerned about a possible macro of the same name. For example, +you may use @code{__aligned__} instead of @code{aligned}. + +@xref{Attribute Syntax}, for details of the exact syntax for using +attributes. + +@table @code +@cindex @code{aligned} attribute +@item aligned (@var{alignment}) +This attribute specifies a minimum alignment for the variable or +structure field, measured in bytes. For example, the declaration: + +@smallexample +int x __attribute__ ((aligned (16))) = 0; +@end smallexample + +@noindent +causes the compiler to allocate the global variable @code{x} on a +16-byte boundary. On a 68040, this could be used in conjunction with +an @code{asm} expression to access the @code{move16} instruction which +requires 16-byte aligned operands. + +You can also specify the alignment of structure fields. For example, to +create a double-word aligned @code{int} pair, you could write: + +@smallexample +struct foo @{ int x[2] __attribute__ ((aligned (8))); @}; +@end smallexample + +@noindent +This is an alternative to creating a union with a @code{double} member +that forces the union to be double-word aligned. + +As in the preceding examples, you can explicitly specify the alignment +(in bytes) that you wish the compiler to use for a given variable or +structure field. Alternatively, you can leave out the alignment factor +and just ask the compiler to align a variable or field to the +default alignment for the target architecture you are compiling for. +The default alignment is sufficient for all scalar types, but may not be +enough for all vector types on a target which supports vector operations. +The default alignment is fixed for a particular target ABI. + +Gcc also provides a target specific macro @code{__BIGGEST_ALIGNMENT__}, +which is the largest alignment ever used for any data type on the +target machine you are compiling for. For example, you could write: + +@smallexample +short array[3] __attribute__ ((aligned (__BIGGEST_ALIGNMENT__))); +@end smallexample + +The compiler automatically sets the alignment for the declared +variable or field to @code{__BIGGEST_ALIGNMENT__}. Doing this can +often make copy operations more efficient, because the compiler can +use whatever instructions copy the biggest chunks of memory when +performing copies to or from the variables or fields that you have +aligned this way. Note that the value of @code{__BIGGEST_ALIGNMENT__} +may change depending on command line options. + +When used on a struct, or struct member, the @code{aligned} attribute can +only increase the alignment; in order to decrease it, the @code{packed} +attribute must be specified as well. When used as part of a typedef, the +@code{aligned} attribute can both increase and decrease alignment, and +specifying the @code{packed} attribute will generate a warning. + +Note that the effectiveness of @code{aligned} attributes may be limited +by inherent limitations in your linker. On many systems, the linker is +only able to arrange for variables to be aligned up to a certain maximum +alignment. (For some linkers, the maximum supported alignment may +be very very small.) If your linker is only able to align variables +up to a maximum of 8 byte alignment, then specifying @code{aligned(16)} +in an @code{__attribute__} will still only provide you with 8 byte +alignment. See your linker documentation for further information. + +The @code{aligned} attribute can also be used for functions +(@pxref{Function Attributes}.) + +@item cleanup (@var{cleanup_function}) +@cindex @code{cleanup} attribute +The @code{cleanup} attribute runs a function when the variable goes +out of scope. This attribute can only be applied to auto function +scope variables; it may not be applied to parameters or variables +with static storage duration. The function must take one parameter, +a pointer to a type compatible with the variable. The return value +of the function (if any) is ignored. + +If @option{-fexceptions} is enabled, then @var{cleanup_function} +will be run during the stack unwinding that happens during the +processing of the exception. Note that the @code{cleanup} attribute +does not allow the exception to be caught, only to perform an action. +It is undefined what happens if @var{cleanup_function} does not +return normally. + +@item common +@itemx nocommon +@cindex @code{common} attribute +@cindex @code{nocommon} attribute +@opindex fcommon +@opindex fno-common +The @code{common} attribute requests GCC to place a variable in +``common'' storage. The @code{nocommon} attribute requests the +opposite---to allocate space for it directly. + +These attributes override the default chosen by the +@option{-fno-common} and @option{-fcommon} flags respectively. + +@item deprecated +@itemx deprecated (@var{msg}) +@cindex @code{deprecated} attribute +The @code{deprecated} attribute results in a warning if the variable +is used anywhere in the source file. This is useful when identifying +variables that are expected to be removed in a future version of a +program. The warning also includes the location of the declaration +of the deprecated variable, to enable users to easily find further +information about why the variable is deprecated, or what they should +do instead. Note that the warning only occurs for uses: + +@smallexample +extern int old_var __attribute__ ((deprecated)); +extern int old_var; +int new_fn () @{ return old_var; @} +@end smallexample + +results in a warning on line 3 but not line 2. The optional msg +argument, which must be a string, will be printed in the warning if +present. + +The @code{deprecated} attribute can also be used for functions and +types (@pxref{Function Attributes}, @pxref{Type Attributes}.) + +@item mode (@var{mode}) +@cindex @code{mode} attribute +This attribute specifies the data type for the declaration---whichever +type corresponds to the mode @var{mode}. This in effect lets you +request an integer or floating point type according to its width. + +You may also specify a mode of @samp{byte} or @samp{__byte__} to +indicate the mode corresponding to a one-byte integer, @samp{word} or +@samp{__word__} for the mode of a one-word integer, and @samp{pointer} +or @samp{__pointer__} for the mode used to represent pointers. + +@item packed +@cindex @code{packed} attribute +The @code{packed} attribute specifies that a variable or structure field +should have the smallest possible alignment---one byte for a variable, +and one bit for a field, unless you specify a larger value with the +@code{aligned} attribute. + +Here is a structure in which the field @code{x} is packed, so that it +immediately follows @code{a}: + +@smallexample +struct foo +@{ + char a; + int x[2] __attribute__ ((packed)); +@}; +@end smallexample + +@emph{Note:} The 4.1, 4.2 and 4.3 series of GCC ignore the +@code{packed} attribute on bit-fields of type @code{char}. This has +been fixed in GCC 4.4 but the change can lead to differences in the +structure layout. See the documentation of +@option{-Wpacked-bitfield-compat} for more information. + +@item section ("@var{section-name}") +@cindex @code{section} variable attribute +Normally, the compiler places the objects it generates in sections like +@code{data} and @code{bss}. Sometimes, however, you need additional sections, +or you need certain particular variables to appear in special sections, +for example to map to special hardware. The @code{section} +attribute specifies that a variable (or function) lives in a particular +section. For example, this small program uses several specific section names: + +@smallexample +struct duart a __attribute__ ((section ("DUART_A"))) = @{ 0 @}; +struct duart b __attribute__ ((section ("DUART_B"))) = @{ 0 @}; +char stack[10000] __attribute__ ((section ("STACK"))) = @{ 0 @}; +int init_data __attribute__ ((section ("INITDATA"))); + +main() +@{ + /* @r{Initialize stack pointer} */ + init_sp (stack + sizeof (stack)); + + /* @r{Initialize initialized data} */ + memcpy (&init_data, &data, &edata - &data); + + /* @r{Turn on the serial ports} */ + init_duart (&a); + init_duart (&b); +@} +@end smallexample + +@noindent +Use the @code{section} attribute with +@emph{global} variables and not @emph{local} variables, +as shown in the example. + +You may use the @code{section} attribute with initialized or +uninitialized global variables but the linker requires +each object be defined once, with the exception that uninitialized +variables tentatively go in the @code{common} (or @code{bss}) section +and can be multiply ``defined''. Using the @code{section} attribute +will change what section the variable goes into and may cause the +linker to issue an error if an uninitialized variable has multiple +definitions. You can force a variable to be initialized with the +@option{-fno-common} flag or the @code{nocommon} attribute. + +Some file formats do not support arbitrary sections so the @code{section} +attribute is not available on all platforms. +If you need to map the entire contents of a module to a particular +section, consider using the facilities of the linker instead. + +@item shared +@cindex @code{shared} variable attribute +On Microsoft Windows, in addition to putting variable definitions in a named +section, the section can also be shared among all running copies of an +executable or DLL@. For example, this small program defines shared data +by putting it in a named section @code{shared} and marking the section +shareable: + +@smallexample +int foo __attribute__((section ("shared"), shared)) = 0; + +int +main() +@{ + /* @r{Read and write foo. All running + copies see the same value.} */ + return 0; +@} +@end smallexample + +@noindent +You may only use the @code{shared} attribute along with @code{section} +attribute with a fully initialized global definition because of the way +linkers work. See @code{section} attribute for more information. + +The @code{shared} attribute is only available on Microsoft Windows@. + +@item tls_model ("@var{tls_model}") +@cindex @code{tls_model} attribute +The @code{tls_model} attribute sets thread-local storage model +(@pxref{Thread-Local}) of a particular @code{__thread} variable, +overriding @option{-ftls-model=} command-line switch on a per-variable +basis. +The @var{tls_model} argument should be one of @code{global-dynamic}, +@code{local-dynamic}, @code{initial-exec} or @code{local-exec}. + +Not all targets support this attribute. + +@item unused +This attribute, attached to a variable, means that the variable is meant +to be possibly unused. GCC will not produce a warning for this +variable. + +@item used +This attribute, attached to a variable, means that the variable must be +emitted even if it appears that the variable is not referenced. + +@item vector_size (@var{bytes}) +This attribute specifies the vector size for the variable, measured in +bytes. For example, the declaration: + +@smallexample +int foo __attribute__ ((vector_size (16))); +@end smallexample + +@noindent +causes the compiler to set the mode for @code{foo}, to be 16 bytes, +divided into @code{int} sized units. Assuming a 32-bit int (a vector of +4 units of 4 bytes), the corresponding mode of @code{foo} will be V4SI@. + +This attribute is only applicable to integral and float scalars, +although arrays, pointers, and function return values are allowed in +conjunction with this construct. + +Aggregates with this attribute are invalid, even if they are of the same +size as a corresponding scalar. For example, the declaration: + +@smallexample +struct S @{ int a; @}; +struct S __attribute__ ((vector_size (16))) foo; +@end smallexample + +@noindent +is invalid even if the size of the structure is the same as the size of +the @code{int}. + +@item selectany +The @code{selectany} attribute causes an initialized global variable to +have link-once semantics. When multiple definitions of the variable are +encountered by the linker, the first is selected and the remainder are +discarded. Following usage by the Microsoft compiler, the linker is told +@emph{not} to warn about size or content differences of the multiple +definitions. + +Although the primary usage of this attribute is for POD types, the +attribute can also be applied to global C++ objects that are initialized +by a constructor. In this case, the static initialization and destruction +code for the object is emitted in each translation defining the object, +but the calls to the constructor and destructor are protected by a +link-once guard variable. + +The @code{selectany} attribute is only available on Microsoft Windows +targets. You can use @code{__declspec (selectany)} as a synonym for +@code{__attribute__ ((selectany))} for compatibility with other +compilers. + +@item weak +The @code{weak} attribute is described in @ref{Function Attributes}. + +@item dllimport +The @code{dllimport} attribute is described in @ref{Function Attributes}. + +@item dllexport +The @code{dllexport} attribute is described in @ref{Function Attributes}. + +@end table + +@subsection AVR Variable Attributes + +@table @code +@item progmem +@cindex @code{progmem} AVR variable attribute +The @code{progmem} attribute is used on the AVR to place data in the program +memory address space (flash). This is accomplished by putting +respective variables into a section whose name starts with @code{.progmem}. + +AVR is a Harvard architecture processor and data and reas only data +normally resides in the data memory address space (RAM). +@end table + +@subsection Blackfin Variable Attributes + +Three attributes are currently defined for the Blackfin. + +@table @code +@item l1_data +@itemx l1_data_A +@itemx l1_data_B +@cindex @code{l1_data} variable attribute +@cindex @code{l1_data_A} variable attribute +@cindex @code{l1_data_B} variable attribute +Use these attributes on the Blackfin to place the variable into L1 Data SRAM. +Variables with @code{l1_data} attribute will be put into the specific section +named @code{.l1.data}. Those with @code{l1_data_A} attribute will be put into +the specific section named @code{.l1.data.A}. Those with @code{l1_data_B} +attribute will be put into the specific section named @code{.l1.data.B}. + +@item l2 +@cindex @code{l2} variable attribute +Use this attribute on the Blackfin to place the variable into L2 SRAM. +Variables with @code{l2} attribute will be put into the specific section +named @code{.l2.data}. +@end table + +@subsection M32R/D Variable Attributes + +One attribute is currently defined for the M32R/D@. + +@table @code +@item model (@var{model-name}) +@cindex variable addressability on the M32R/D +Use this attribute on the M32R/D to set the addressability of an object. +The identifier @var{model-name} is one of @code{small}, @code{medium}, +or @code{large}, representing each of the code models. + +Small model objects live in the lower 16MB of memory (so that their +addresses can be loaded with the @code{ld24} instruction). + +Medium and large model objects may live anywhere in the 32-bit address space +(the compiler will generate @code{seth/add3} instructions to load their +addresses). +@end table + +@anchor{MeP Variable Attributes} +@subsection MeP Variable Attributes + +The MeP target has a number of addressing modes and busses. The +@code{near} space spans the standard memory space's first 16 megabytes +(24 bits). The @code{far} space spans the entire 32-bit memory space. +The @code{based} space is a 128 byte region in the memory space which +is addressed relative to the @code{$tp} register. The @code{tiny} +space is a 65536 byte region relative to the @code{$gp} register. In +addition to these memory regions, the MeP target has a separate 16-bit +control bus which is specified with @code{cb} attributes. + +@table @code + +@item based +Any variable with the @code{based} attribute will be assigned to the +@code{.based} section, and will be accessed with relative to the +@code{$tp} register. + +@item tiny +Likewise, the @code{tiny} attribute assigned variables to the +@code{.tiny} section, relative to the @code{$gp} register. + +@item near +Variables with the @code{near} attribute are assumed to have addresses +that fit in a 24-bit addressing mode. This is the default for large +variables (@code{-mtiny=4} is the default) but this attribute can +override @code{-mtiny=} for small variables, or override @code{-ml}. + +@item far +Variables with the @code{far} attribute are addressed using a full +32-bit address. Since this covers the entire memory space, this +allows modules to make no assumptions about where variables might be +stored. + +@item io +@itemx io (@var{addr}) +Variables with the @code{io} attribute are used to address +memory-mapped peripherals. If an address is specified, the variable +is assigned that address, else it is not assigned an address (it is +assumed some other module will assign an address). Example: + +@example +int timer_count __attribute__((io(0x123))); +@end example + +@item cb +@itemx cb (@var{addr}) +Variables with the @code{cb} attribute are used to access the control +bus, using special instructions. @code{addr} indicates the control bus +address. Example: + +@example +int cpu_clock __attribute__((cb(0x123))); +@end example + +@end table + +@anchor{i386 Variable Attributes} +@subsection i386 Variable Attributes + +Two attributes are currently defined for i386 configurations: +@code{ms_struct} and @code{gcc_struct} + +@table @code +@item ms_struct +@itemx gcc_struct +@cindex @code{ms_struct} attribute +@cindex @code{gcc_struct} attribute + +If @code{packed} is used on a structure, or if bit-fields are used +it may be that the Microsoft ABI packs them differently +than GCC would normally pack them. Particularly when moving packed +data between functions compiled with GCC and the native Microsoft compiler +(either via function call or as data in a file), it may be necessary to access +either format. + +Currently @option{-m[no-]ms-bitfields} is provided for the Microsoft Windows X86 +compilers to match the native Microsoft compiler. + +The Microsoft structure layout algorithm is fairly simple with the exception +of the bitfield packing: + +The padding and alignment of members of structures and whether a bit field +can straddle a storage-unit boundary + +@enumerate +@item Structure members are stored sequentially in the order in which they are +declared: the first member has the lowest memory address and the last member +the highest. + +@item Every data object has an alignment-requirement. The alignment-requirement +for all data except structures, unions, and arrays is either the size of the +object or the current packing size (specified with either the aligned attribute +or the pack pragma), whichever is less. For structures, unions, and arrays, +the alignment-requirement is the largest alignment-requirement of its members. +Every object is allocated an offset so that: + +offset % alignment-requirement == 0 + +@item Adjacent bit fields are packed into the same 1-, 2-, or 4-byte allocation +unit if the integral types are the same size and if the next bit field fits +into the current allocation unit without crossing the boundary imposed by the +common alignment requirements of the bit fields. +@end enumerate + +Handling of zero-length bitfields: + +MSVC interprets zero-length bitfields in the following ways: + +@enumerate +@item If a zero-length bitfield is inserted between two bitfields that would +normally be coalesced, the bitfields will not be coalesced. + +For example: + +@smallexample +struct + @{ + unsigned long bf_1 : 12; + unsigned long : 0; + unsigned long bf_2 : 12; + @} t1; +@end smallexample + +The size of @code{t1} would be 8 bytes with the zero-length bitfield. If the +zero-length bitfield were removed, @code{t1}'s size would be 4 bytes. + +@item If a zero-length bitfield is inserted after a bitfield, @code{foo}, and the +alignment of the zero-length bitfield is greater than the member that follows it, +@code{bar}, @code{bar} will be aligned as the type of the zero-length bitfield. + +For example: + +@smallexample +struct + @{ + char foo : 4; + short : 0; + char bar; + @} t2; + +struct + @{ + char foo : 4; + short : 0; + double bar; + @} t3; +@end smallexample + +For @code{t2}, @code{bar} will be placed at offset 2, rather than offset 1. +Accordingly, the size of @code{t2} will be 4. For @code{t3}, the zero-length +bitfield will not affect the alignment of @code{bar} or, as a result, the size +of the structure. + +Taking this into account, it is important to note the following: + +@enumerate +@item If a zero-length bitfield follows a normal bitfield, the type of the +zero-length bitfield may affect the alignment of the structure as whole. For +example, @code{t2} has a size of 4 bytes, since the zero-length bitfield follows a +normal bitfield, and is of type short. + +@item Even if a zero-length bitfield is not followed by a normal bitfield, it may +still affect the alignment of the structure: + +@smallexample +struct + @{ + char foo : 6; + long : 0; + @} t4; +@end smallexample + +Here, @code{t4} will take up 4 bytes. +@end enumerate + +@item Zero-length bitfields following non-bitfield members are ignored: + +@smallexample +struct + @{ + char foo; + long : 0; + char bar; + @} t5; +@end smallexample + +Here, @code{t5} will take up 2 bytes. +@end enumerate +@end table + +@subsection PowerPC Variable Attributes + +Three attributes currently are defined for PowerPC configurations: +@code{altivec}, @code{ms_struct} and @code{gcc_struct}. + +For full documentation of the struct attributes please see the +documentation in @ref{i386 Variable Attributes}. + +For documentation of @code{altivec} attribute please see the +documentation in @ref{PowerPC Type Attributes}. + +@subsection SPU Variable Attributes + +The SPU supports the @code{spu_vector} attribute for variables. For +documentation of this attribute please see the documentation in +@ref{SPU Type Attributes}. + +@subsection Xstormy16 Variable Attributes + +One attribute is currently defined for xstormy16 configurations: +@code{below100}. + +@table @code +@item below100 +@cindex @code{below100} attribute + +If a variable has the @code{below100} attribute (@code{BELOW100} is +allowed also), GCC will place the variable in the first 0x100 bytes of +memory and use special opcodes to access it. Such variables will be +placed in either the @code{.bss_below100} section or the +@code{.data_below100} section. + +@end table + +@node Type Attributes +@section Specifying Attributes of Types +@cindex attribute of types +@cindex type attributes + +The keyword @code{__attribute__} allows you to specify special +attributes of @code{struct} and @code{union} types when you define +such types. This keyword is followed by an attribute specification +inside double parentheses. Seven attributes are currently defined for +types: @code{aligned}, @code{packed}, @code{transparent_union}, +@code{unused}, @code{deprecated}, @code{visibility}, and +@code{may_alias}. Other attributes are defined for functions +(@pxref{Function Attributes}) and for variables (@pxref{Variable +Attributes}). + +You may also specify any one of these attributes with @samp{__} +preceding and following its keyword. This allows you to use these +attributes in header files without being concerned about a possible +macro of the same name. For example, you may use @code{__aligned__} +instead of @code{aligned}. + +You may specify type attributes in an enum, struct or union type +declaration or definition, or for other types in a @code{typedef} +declaration. + +For an enum, struct or union type, you may specify attributes either +between the enum, struct or union tag and the name of the type, or +just past the closing curly brace of the @emph{definition}. The +former syntax is preferred. + +@xref{Attribute Syntax}, for details of the exact syntax for using +attributes. + +@table @code +@cindex @code{aligned} attribute +@item aligned (@var{alignment}) +This attribute specifies a minimum alignment (in bytes) for variables +of the specified type. For example, the declarations: + +@smallexample +struct S @{ short f[3]; @} __attribute__ ((aligned (8))); +typedef int more_aligned_int __attribute__ ((aligned (8))); +@end smallexample + +@noindent +force the compiler to insure (as far as it can) that each variable whose +type is @code{struct S} or @code{more_aligned_int} will be allocated and +aligned @emph{at least} on a 8-byte boundary. On a SPARC, having all +variables of type @code{struct S} aligned to 8-byte boundaries allows +the compiler to use the @code{ldd} and @code{std} (doubleword load and +store) instructions when copying one variable of type @code{struct S} to +another, thus improving run-time efficiency. + +Note that the alignment of any given @code{struct} or @code{union} type +is required by the ISO C standard to be at least a perfect multiple of +the lowest common multiple of the alignments of all of the members of +the @code{struct} or @code{union} in question. This means that you @emph{can} +effectively adjust the alignment of a @code{struct} or @code{union} +type by attaching an @code{aligned} attribute to any one of the members +of such a type, but the notation illustrated in the example above is a +more obvious, intuitive, and readable way to request the compiler to +adjust the alignment of an entire @code{struct} or @code{union} type. + +As in the preceding example, you can explicitly specify the alignment +(in bytes) that you wish the compiler to use for a given @code{struct} +or @code{union} type. Alternatively, you can leave out the alignment factor +and just ask the compiler to align a type to the maximum +useful alignment for the target machine you are compiling for. For +example, you could write: + +@smallexample +struct S @{ short f[3]; @} __attribute__ ((aligned)); +@end smallexample + +Whenever you leave out the alignment factor in an @code{aligned} +attribute specification, the compiler automatically sets the alignment +for the type to the largest alignment which is ever used for any data +type on the target machine you are compiling for. Doing this can often +make copy operations more efficient, because the compiler can use +whatever instructions copy the biggest chunks of memory when performing +copies to or from the variables which have types that you have aligned +this way. + +In the example above, if the size of each @code{short} is 2 bytes, then +the size of the entire @code{struct S} type is 6 bytes. The smallest +power of two which is greater than or equal to that is 8, so the +compiler sets the alignment for the entire @code{struct S} type to 8 +bytes. + +Note that although you can ask the compiler to select a time-efficient +alignment for a given type and then declare only individual stand-alone +objects of that type, the compiler's ability to select a time-efficient +alignment is primarily useful only when you plan to create arrays of +variables having the relevant (efficiently aligned) type. If you +declare or use arrays of variables of an efficiently-aligned type, then +it is likely that your program will also be doing pointer arithmetic (or +subscripting, which amounts to the same thing) on pointers to the +relevant type, and the code that the compiler generates for these +pointer arithmetic operations will often be more efficient for +efficiently-aligned types than for other types. + +The @code{aligned} attribute can only increase the alignment; but you +can decrease it by specifying @code{packed} as well. See below. + +Note that the effectiveness of @code{aligned} attributes may be limited +by inherent limitations in your linker. On many systems, the linker is +only able to arrange for variables to be aligned up to a certain maximum +alignment. (For some linkers, the maximum supported alignment may +be very very small.) If your linker is only able to align variables +up to a maximum of 8 byte alignment, then specifying @code{aligned(16)} +in an @code{__attribute__} will still only provide you with 8 byte +alignment. See your linker documentation for further information. + +@item packed +This attribute, attached to @code{struct} or @code{union} type +definition, specifies that each member (other than zero-width bitfields) +of the structure or union is placed to minimize the memory required. When +attached to an @code{enum} definition, it indicates that the smallest +integral type should be used. + +@opindex fshort-enums +Specifying this attribute for @code{struct} and @code{union} types is +equivalent to specifying the @code{packed} attribute on each of the +structure or union members. Specifying the @option{-fshort-enums} +flag on the line is equivalent to specifying the @code{packed} +attribute on all @code{enum} definitions. + +In the following example @code{struct my_packed_struct}'s members are +packed closely together, but the internal layout of its @code{s} member +is not packed---to do that, @code{struct my_unpacked_struct} would need to +be packed too. + +@smallexample +struct my_unpacked_struct + @{ + char c; + int i; + @}; + +struct __attribute__ ((__packed__)) my_packed_struct + @{ + char c; + int i; + struct my_unpacked_struct s; + @}; +@end smallexample + +You may only specify this attribute on the definition of an @code{enum}, +@code{struct} or @code{union}, not on a @code{typedef} which does not +also define the enumerated type, structure or union. + +@item transparent_union +This attribute, attached to a @code{union} type definition, indicates +that any function parameter having that union type causes calls to that +function to be treated in a special way. + +First, the argument corresponding to a transparent union type can be of +any type in the union; no cast is required. Also, if the union contains +a pointer type, the corresponding argument can be a null pointer +constant or a void pointer expression; and if the union contains a void +pointer type, the corresponding argument can be any pointer expression. +If the union member type is a pointer, qualifiers like @code{const} on +the referenced type must be respected, just as with normal pointer +conversions. + +Second, the argument is passed to the function using the calling +conventions of the first member of the transparent union, not the calling +conventions of the union itself. All members of the union must have the +same machine representation; this is necessary for this argument passing +to work properly. + +Transparent unions are designed for library functions that have multiple +interfaces for compatibility reasons. For example, suppose the +@code{wait} function must accept either a value of type @code{int *} to +comply with Posix, or a value of type @code{union wait *} to comply with +the 4.1BSD interface. If @code{wait}'s parameter were @code{void *}, +@code{wait} would accept both kinds of arguments, but it would also +accept any other pointer type and this would make argument type checking +less useful. Instead, @code{<sys/wait.h>} might define the interface +as follows: + +@smallexample +typedef union __attribute__ ((__transparent_union__)) + @{ + int *__ip; + union wait *__up; + @} wait_status_ptr_t; + +pid_t wait (wait_status_ptr_t); +@end smallexample + +This interface allows either @code{int *} or @code{union wait *} +arguments to be passed, using the @code{int *} calling convention. +The program can call @code{wait} with arguments of either type: + +@smallexample +int w1 () @{ int w; return wait (&w); @} +int w2 () @{ union wait w; return wait (&w); @} +@end smallexample + +With this interface, @code{wait}'s implementation might look like this: + +@smallexample +pid_t wait (wait_status_ptr_t p) +@{ + return waitpid (-1, p.__ip, 0); +@} +@end smallexample + +@item unused +When attached to a type (including a @code{union} or a @code{struct}), +this attribute means that variables of that type are meant to appear +possibly unused. GCC will not produce a warning for any variables of +that type, even if the variable appears to do nothing. This is often +the case with lock or thread classes, which are usually defined and then +not referenced, but contain constructors and destructors that have +nontrivial bookkeeping functions. + +@item deprecated +@itemx deprecated (@var{msg}) +The @code{deprecated} attribute results in a warning if the type +is used anywhere in the source file. This is useful when identifying +types that are expected to be removed in a future version of a program. +If possible, the warning also includes the location of the declaration +of the deprecated type, to enable users to easily find further +information about why the type is deprecated, or what they should do +instead. Note that the warnings only occur for uses and then only +if the type is being applied to an identifier that itself is not being +declared as deprecated. + +@smallexample +typedef int T1 __attribute__ ((deprecated)); +T1 x; +typedef T1 T2; +T2 y; +typedef T1 T3 __attribute__ ((deprecated)); +T3 z __attribute__ ((deprecated)); +@end smallexample + +results in a warning on line 2 and 3 but not lines 4, 5, or 6. No +warning is issued for line 4 because T2 is not explicitly +deprecated. Line 5 has no warning because T3 is explicitly +deprecated. Similarly for line 6. The optional msg +argument, which must be a string, will be printed in the warning if +present. + +The @code{deprecated} attribute can also be used for functions and +variables (@pxref{Function Attributes}, @pxref{Variable Attributes}.) + +@item may_alias +Accesses through pointers to types with this attribute are not subject +to type-based alias analysis, but are instead assumed to be able to alias +any other type of objects. In the context of 6.5/7 an lvalue expression +dereferencing such a pointer is treated like having a character type. +See @option{-fstrict-aliasing} for more information on aliasing issues. +This extension exists to support some vector APIs, in which pointers to +one vector type are permitted to alias pointers to a different vector type. + +Note that an object of a type with this attribute does not have any +special semantics. + +Example of use: + +@smallexample +typedef short __attribute__((__may_alias__)) short_a; + +int +main (void) +@{ + int a = 0x12345678; + short_a *b = (short_a *) &a; + + b[1] = 0; + + if (a == 0x12345678) + abort(); + + exit(0); +@} +@end smallexample + +If you replaced @code{short_a} with @code{short} in the variable +declaration, the above program would abort when compiled with +@option{-fstrict-aliasing}, which is on by default at @option{-O2} or +above in recent GCC versions. + +@item visibility +In C++, attribute visibility (@pxref{Function Attributes}) can also be +applied to class, struct, union and enum types. Unlike other type +attributes, the attribute must appear between the initial keyword and +the name of the type; it cannot appear after the body of the type. + +Note that the type visibility is applied to vague linkage entities +associated with the class (vtable, typeinfo node, etc.). In +particular, if a class is thrown as an exception in one shared object +and caught in another, the class must have default visibility. +Otherwise the two shared objects will be unable to use the same +typeinfo node and exception handling will break. + +@end table + +@subsection ARM Type Attributes + +On those ARM targets that support @code{dllimport} (such as Symbian +OS), you can use the @code{notshared} attribute to indicate that the +virtual table and other similar data for a class should not be +exported from a DLL@. For example: + +@smallexample +class __declspec(notshared) C @{ +public: + __declspec(dllimport) C(); + virtual void f(); +@} + +__declspec(dllexport) +C::C() @{@} +@end smallexample + +In this code, @code{C::C} is exported from the current DLL, but the +virtual table for @code{C} is not exported. (You can use +@code{__attribute__} instead of @code{__declspec} if you prefer, but +most Symbian OS code uses @code{__declspec}.) + +@anchor{MeP Type Attributes} +@subsection MeP Type Attributes + +Many of the MeP variable attributes may be applied to types as well. +Specifically, the @code{based}, @code{tiny}, @code{near}, and +@code{far} attributes may be applied to either. The @code{io} and +@code{cb} attributes may not be applied to types. + +@anchor{i386 Type Attributes} +@subsection i386 Type Attributes + +Two attributes are currently defined for i386 configurations: +@code{ms_struct} and @code{gcc_struct}. + +@table @code + +@item ms_struct +@itemx gcc_struct +@cindex @code{ms_struct} +@cindex @code{gcc_struct} + +If @code{packed} is used on a structure, or if bit-fields are used +it may be that the Microsoft ABI packs them differently +than GCC would normally pack them. Particularly when moving packed +data between functions compiled with GCC and the native Microsoft compiler +(either via function call or as data in a file), it may be necessary to access +either format. + +Currently @option{-m[no-]ms-bitfields} is provided for the Microsoft Windows X86 +compilers to match the native Microsoft compiler. +@end table + +To specify multiple attributes, separate them by commas within the +double parentheses: for example, @samp{__attribute__ ((aligned (16), +packed))}. + +@anchor{PowerPC Type Attributes} +@subsection PowerPC Type Attributes + +Three attributes currently are defined for PowerPC configurations: +@code{altivec}, @code{ms_struct} and @code{gcc_struct}. + +For full documentation of the @code{ms_struct} and @code{gcc_struct} +attributes please see the documentation in @ref{i386 Type Attributes}. + +The @code{altivec} attribute allows one to declare AltiVec vector data +types supported by the AltiVec Programming Interface Manual. The +attribute requires an argument to specify one of three vector types: +@code{vector__}, @code{pixel__} (always followed by unsigned short), +and @code{bool__} (always followed by unsigned). + +@smallexample +__attribute__((altivec(vector__))) +__attribute__((altivec(pixel__))) unsigned short +__attribute__((altivec(bool__))) unsigned +@end smallexample + +These attributes mainly are intended to support the @code{__vector}, +@code{__pixel}, and @code{__bool} AltiVec keywords. + +@anchor{SPU Type Attributes} +@subsection SPU Type Attributes + +The SPU supports the @code{spu_vector} attribute for types. This attribute +allows one to declare vector data types supported by the Sony/Toshiba/IBM SPU +Language Extensions Specification. It is intended to support the +@code{__vector} keyword. + +@node Alignment +@section Inquiring on Alignment of Types or Variables +@cindex alignment +@cindex type alignment +@cindex variable alignment + +The keyword @code{__alignof__} allows you to inquire about how an object +is aligned, or the minimum alignment usually required by a type. Its +syntax is just like @code{sizeof}. + +For example, if the target machine requires a @code{double} value to be +aligned on an 8-byte boundary, then @code{__alignof__ (double)} is 8. +This is true on many RISC machines. On more traditional machine +designs, @code{__alignof__ (double)} is 4 or even 2. + +Some machines never actually require alignment; they allow reference to any +data type even at an odd address. For these machines, @code{__alignof__} +reports the smallest alignment that GCC will give the data type, usually as +mandated by the target ABI. + +If the operand of @code{__alignof__} is an lvalue rather than a type, +its value is the required alignment for its type, taking into account +any minimum alignment specified with GCC's @code{__attribute__} +extension (@pxref{Variable Attributes}). For example, after this +declaration: + +@smallexample +struct foo @{ int x; char y; @} foo1; +@end smallexample + +@noindent +the value of @code{__alignof__ (foo1.y)} is 1, even though its actual +alignment is probably 2 or 4, the same as @code{__alignof__ (int)}. + +It is an error to ask for the alignment of an incomplete type. + + +@node Inline +@section An Inline Function is As Fast As a Macro +@cindex inline functions +@cindex integrating function code +@cindex open coding +@cindex macros, inline alternative + +By declaring a function inline, you can direct GCC to make +calls to that function faster. One way GCC can achieve this is to +integrate that function's code into the code for its callers. This +makes execution faster by eliminating the function-call overhead; in +addition, if any of the actual argument values are constant, their +known values may permit simplifications at compile time so that not +all of the inline function's code needs to be included. The effect on +code size is less predictable; object code may be larger or smaller +with function inlining, depending on the particular case. You can +also direct GCC to try to integrate all ``simple enough'' functions +into their callers with the option @option{-finline-functions}. + +GCC implements three different semantics of declaring a function +inline. One is available with @option{-std=gnu89} or +@option{-fgnu89-inline} or when @code{gnu_inline} attribute is present +on all inline declarations, another when +@option{-std=c99}, @option{-std=c1x}, +@option{-std=gnu99} or @option{-std=gnu1x} +(without @option{-fgnu89-inline}), and the third +is used when compiling C++. + +To declare a function inline, use the @code{inline} keyword in its +declaration, like this: + +@smallexample +static inline int +inc (int *a) +@{ + return (*a)++; +@} +@end smallexample + +If you are writing a header file to be included in ISO C90 programs, write +@code{__inline__} instead of @code{inline}. @xref{Alternate Keywords}. + +The three types of inlining behave similarly in two important cases: +when the @code{inline} keyword is used on a @code{static} function, +like the example above, and when a function is first declared without +using the @code{inline} keyword and then is defined with +@code{inline}, like this: + +@smallexample +extern int inc (int *a); +inline int +inc (int *a) +@{ + return (*a)++; +@} +@end smallexample + +In both of these common cases, the program behaves the same as if you +had not used the @code{inline} keyword, except for its speed. + +@cindex inline functions, omission of +@opindex fkeep-inline-functions +When a function is both inline and @code{static}, if all calls to the +function are integrated into the caller, and the function's address is +never used, then the function's own assembler code is never referenced. +In this case, GCC does not actually output assembler code for the +function, unless you specify the option @option{-fkeep-inline-functions}. +Some calls cannot be integrated for various reasons (in particular, +calls that precede the function's definition cannot be integrated, and +neither can recursive calls within the definition). If there is a +nonintegrated call, then the function is compiled to assembler code as +usual. The function must also be compiled as usual if the program +refers to its address, because that can't be inlined. + +@opindex Winline +Note that certain usages in a function definition can make it unsuitable +for inline substitution. Among these usages are: use of varargs, use of +alloca, use of variable sized data types (@pxref{Variable Length}), +use of computed goto (@pxref{Labels as Values}), use of nonlocal goto, +and nested functions (@pxref{Nested Functions}). Using @option{-Winline} +will warn when a function marked @code{inline} could not be substituted, +and will give the reason for the failure. + +@cindex automatic @code{inline} for C++ member fns +@cindex @code{inline} automatic for C++ member fns +@cindex member fns, automatically @code{inline} +@cindex C++ member fns, automatically @code{inline} +@opindex fno-default-inline +As required by ISO C++, GCC considers member functions defined within +the body of a class to be marked inline even if they are +not explicitly declared with the @code{inline} keyword. You can +override this with @option{-fno-default-inline}; @pxref{C++ Dialect +Options,,Options Controlling C++ Dialect}. + +GCC does not inline any functions when not optimizing unless you specify +the @samp{always_inline} attribute for the function, like this: + +@smallexample +/* @r{Prototype.} */ +inline void foo (const char) __attribute__((always_inline)); +@end smallexample + +The remainder of this section is specific to GNU C90 inlining. + +@cindex non-static inline function +When an inline function is not @code{static}, then the compiler must assume +that there may be calls from other source files; since a global symbol can +be defined only once in any program, the function must not be defined in +the other source files, so the calls therein cannot be integrated. +Therefore, a non-@code{static} inline function is always compiled on its +own in the usual fashion. + +If you specify both @code{inline} and @code{extern} in the function +definition, then the definition is used only for inlining. In no case +is the function compiled on its own, not even if you refer to its +address explicitly. Such an address becomes an external reference, as +if you had only declared the function, and had not defined it. + +This combination of @code{inline} and @code{extern} has almost the +effect of a macro. The way to use it is to put a function definition in +a header file with these keywords, and put another copy of the +definition (lacking @code{inline} and @code{extern}) in a library file. +The definition in the header file will cause most calls to the function +to be inlined. If any uses of the function remain, they will refer to +the single copy in the library. + +@node Volatiles +@section When is a Volatile Object Accessed? +@cindex accessing volatiles +@cindex volatile read +@cindex volatile write +@cindex volatile access + +C has the concept of volatile objects. These are normally accessed by +pointers and used for accessing hardware or inter-thread +communication. The standard encourages compilers to refrain from +optimizations concerning accesses to volatile objects, but leaves it +implementation defined as to what constitutes a volatile access. The +minimum requirement is that at a sequence point all previous accesses +to volatile objects have stabilized and no subsequent accesses have +occurred. Thus an implementation is free to reorder and combine +volatile accesses which occur between sequence points, but cannot do +so for accesses across a sequence point. The use of volatile does +not allow you to violate the restriction on updating objects multiple +times between two sequence points. + +Accesses to non-volatile objects are not ordered with respect to +volatile accesses. You cannot use a volatile object as a memory +barrier to order a sequence of writes to non-volatile memory. For +instance: + +@smallexample +int *ptr = @var{something}; +volatile int vobj; +*ptr = @var{something}; +vobj = 1; +@end smallexample + +Unless @var{*ptr} and @var{vobj} can be aliased, it is not guaranteed +that the write to @var{*ptr} will have occurred by the time the update +of @var{vobj} has happened. If you need this guarantee, you must use +a stronger memory barrier such as: + +@smallexample +int *ptr = @var{something}; +volatile int vobj; +*ptr = @var{something}; +asm volatile ("" : : : "memory"); +vobj = 1; +@end smallexample + +A scalar volatile object is read when it is accessed in a void context: + +@smallexample +volatile int *src = @var{somevalue}; +*src; +@end smallexample + +Such expressions are rvalues, and GCC implements this as a +read of the volatile object being pointed to. + +Assignments are also expressions and have an rvalue. However when +assigning to a scalar volatile, the volatile object is not reread, +regardless of whether the assignment expression's rvalue is used or +not. If the assignment's rvalue is used, the value is that assigned +to the volatile object. For instance, there is no read of @var{vobj} +in all the following cases: + +@smallexample +int obj; +volatile int vobj; +vobj = @var{something}; +obj = vobj = @var{something}; +obj ? vobj = @var{onething} : vobj = @var{anotherthing}; +obj = (@var{something}, vobj = @var{anotherthing}); +@end smallexample + +If you need to read the volatile object after an assignment has +occurred, you must use a separate expression with an intervening +sequence point. + +As bitfields are not individually addressable, volatile bitfields may +be implicitly read when written to, or when adjacent bitfields are +accessed. Bitfield operations may be optimized such that adjacent +bitfields are only partially accessed, if they straddle a storage unit +boundary. For these reasons it is unwise to use volatile bitfields to +access hardware. + +@node Extended Asm +@section Assembler Instructions with C Expression Operands +@cindex extended @code{asm} +@cindex @code{asm} expressions +@cindex assembler instructions +@cindex registers + +In an assembler instruction using @code{asm}, you can specify the +operands of the instruction using C expressions. This means you need not +guess which registers or memory locations will contain the data you want +to use. + +You must specify an assembler instruction template much like what +appears in a machine description, plus an operand constraint string for +each operand. + +For example, here is how to use the 68881's @code{fsinx} instruction: + +@smallexample +asm ("fsinx %1,%0" : "=f" (result) : "f" (angle)); +@end smallexample + +@noindent +Here @code{angle} is the C expression for the input operand while +@code{result} is that of the output operand. Each has @samp{"f"} as its +operand constraint, saying that a floating point register is required. +The @samp{=} in @samp{=f} indicates that the operand is an output; all +output operands' constraints must use @samp{=}. The constraints use the +same language used in the machine description (@pxref{Constraints}). + +Each operand is described by an operand-constraint string followed by +the C expression in parentheses. A colon separates the assembler +template from the first output operand and another separates the last +output operand from the first input, if any. Commas separate the +operands within each group. The total number of operands is currently +limited to 30; this limitation may be lifted in some future version of +GCC@. + +If there are no output operands but there are input operands, you must +place two consecutive colons surrounding the place where the output +operands would go. + +As of GCC version 3.1, it is also possible to specify input and output +operands using symbolic names which can be referenced within the +assembler code. These names are specified inside square brackets +preceding the constraint string, and can be referenced inside the +assembler code using @code{%[@var{name}]} instead of a percentage sign +followed by the operand number. Using named operands the above example +could look like: + +@smallexample +asm ("fsinx %[angle],%[output]" + : [output] "=f" (result) + : [angle] "f" (angle)); +@end smallexample + +@noindent +Note that the symbolic operand names have no relation whatsoever to +other C identifiers. You may use any name you like, even those of +existing C symbols, but you must ensure that no two operands within the same +assembler construct use the same symbolic name. + +Output operand expressions must be lvalues; the compiler can check this. +The input operands need not be lvalues. The compiler cannot check +whether the operands have data types that are reasonable for the +instruction being executed. It does not parse the assembler instruction +template and does not know what it means or even whether it is valid +assembler input. The extended @code{asm} feature is most often used for +machine instructions the compiler itself does not know exist. If +the output expression cannot be directly addressed (for example, it is a +bit-field), your constraint must allow a register. In that case, GCC +will use the register as the output of the @code{asm}, and then store +that register into the output. + +The ordinary output operands must be write-only; GCC will assume that +the values in these operands before the instruction are dead and need +not be generated. Extended asm supports input-output or read-write +operands. Use the constraint character @samp{+} to indicate such an +operand and list it with the output operands. You should only use +read-write operands when the constraints for the operand (or the +operand in which only some of the bits are to be changed) allow a +register. + +You may, as an alternative, logically split its function into two +separate operands, one input operand and one write-only output +operand. The connection between them is expressed by constraints +which say they need to be in the same location when the instruction +executes. You can use the same C expression for both operands, or +different expressions. For example, here we write the (fictitious) +@samp{combine} instruction with @code{bar} as its read-only source +operand and @code{foo} as its read-write destination: + +@smallexample +asm ("combine %2,%0" : "=r" (foo) : "0" (foo), "g" (bar)); +@end smallexample + +@noindent +The constraint @samp{"0"} for operand 1 says that it must occupy the +same location as operand 0. A number in constraint is allowed only in +an input operand and it must refer to an output operand. + +Only a number in the constraint can guarantee that one operand will be in +the same place as another. The mere fact that @code{foo} is the value +of both operands is not enough to guarantee that they will be in the +same place in the generated assembler code. The following would not +work reliably: + +@smallexample +asm ("combine %2,%0" : "=r" (foo) : "r" (foo), "g" (bar)); +@end smallexample + +Various optimizations or reloading could cause operands 0 and 1 to be in +different registers; GCC knows no reason not to do so. For example, the +compiler might find a copy of the value of @code{foo} in one register and +use it for operand 1, but generate the output operand 0 in a different +register (copying it afterward to @code{foo}'s own address). Of course, +since the register for operand 1 is not even mentioned in the assembler +code, the result will not work, but GCC can't tell that. + +As of GCC version 3.1, one may write @code{[@var{name}]} instead of +the operand number for a matching constraint. For example: + +@smallexample +asm ("cmoveq %1,%2,%[result]" + : [result] "=r"(result) + : "r" (test), "r"(new), "[result]"(old)); +@end smallexample + +Sometimes you need to make an @code{asm} operand be a specific register, +but there's no matching constraint letter for that register @emph{by +itself}. To force the operand into that register, use a local variable +for the operand and specify the register in the variable declaration. +@xref{Explicit Reg Vars}. Then for the @code{asm} operand, use any +register constraint letter that matches the register: + +@smallexample +register int *p1 asm ("r0") = @dots{}; +register int *p2 asm ("r1") = @dots{}; +register int *result asm ("r0"); +asm ("sysint" : "=r" (result) : "0" (p1), "r" (p2)); +@end smallexample + +@anchor{Example of asm with clobbered asm reg} +In the above example, beware that a register that is call-clobbered by +the target ABI will be overwritten by any function call in the +assignment, including library calls for arithmetic operators. +Also a register may be clobbered when generating some operations, +like variable shift, memory copy or memory move on x86. +Assuming it is a call-clobbered register, this may happen to @code{r0} +above by the assignment to @code{p2}. If you have to use such a +register, use temporary variables for expressions between the register +assignment and use: + +@smallexample +int t1 = @dots{}; +register int *p1 asm ("r0") = @dots{}; +register int *p2 asm ("r1") = t1; +register int *result asm ("r0"); +asm ("sysint" : "=r" (result) : "0" (p1), "r" (p2)); +@end smallexample + +Some instructions clobber specific hard registers. To describe this, +write a third colon after the input operands, followed by the names of +the clobbered hard registers (given as strings). Here is a realistic +example for the VAX: + +@smallexample +asm volatile ("movc3 %0,%1,%2" + : /* @r{no outputs} */ + : "g" (from), "g" (to), "g" (count) + : "r0", "r1", "r2", "r3", "r4", "r5"); +@end smallexample + +You may not write a clobber description in a way that overlaps with an +input or output operand. For example, you may not have an operand +describing a register class with one member if you mention that register +in the clobber list. Variables declared to live in specific registers +(@pxref{Explicit Reg Vars}), and used as asm input or output operands must +have no part mentioned in the clobber description. +There is no way for you to specify that an input +operand is modified without also specifying it as an output +operand. Note that if all the output operands you specify are for this +purpose (and hence unused), you will then also need to specify +@code{volatile} for the @code{asm} construct, as described below, to +prevent GCC from deleting the @code{asm} statement as unused. + +If you refer to a particular hardware register from the assembler code, +you will probably have to list the register after the third colon to +tell the compiler the register's value is modified. In some assemblers, +the register names begin with @samp{%}; to produce one @samp{%} in the +assembler code, you must write @samp{%%} in the input. + +If your assembler instruction can alter the condition code register, add +@samp{cc} to the list of clobbered registers. GCC on some machines +represents the condition codes as a specific hardware register; +@samp{cc} serves to name this register. On other machines, the +condition code is handled differently, and specifying @samp{cc} has no +effect. But it is valid no matter what the machine. + +If your assembler instructions access memory in an unpredictable +fashion, add @samp{memory} to the list of clobbered registers. This +will cause GCC to not keep memory values cached in registers across the +assembler instruction and not optimize stores or loads to that memory. +You will also want to add the @code{volatile} keyword if the memory +affected is not listed in the inputs or outputs of the @code{asm}, as +the @samp{memory} clobber does not count as a side-effect of the +@code{asm}. If you know how large the accessed memory is, you can add +it as input or output but if this is not known, you should add +@samp{memory}. As an example, if you access ten bytes of a string, you +can use a memory input like: + +@smallexample +@{"m"( (@{ struct @{ char x[10]; @} *p = (void *)ptr ; *p; @}) )@}. +@end smallexample + +Note that in the following example the memory input is necessary, +otherwise GCC might optimize the store to @code{x} away: +@smallexample +int foo () +@{ + int x = 42; + int *y = &x; + int result; + asm ("magic stuff accessing an 'int' pointed to by '%1'" + "=&d" (r) : "a" (y), "m" (*y)); + return result; +@} +@end smallexample + +You can put multiple assembler instructions together in a single +@code{asm} template, separated by the characters normally used in assembly +code for the system. A combination that works in most places is a newline +to break the line, plus a tab character to move to the instruction field +(written as @samp{\n\t}). Sometimes semicolons can be used, if the +assembler allows semicolons as a line-breaking character. Note that some +assembler dialects use semicolons to start a comment. +The input operands are guaranteed not to use any of the clobbered +registers, and neither will the output operands' addresses, so you can +read and write the clobbered registers as many times as you like. Here +is an example of multiple instructions in a template; it assumes the +subroutine @code{_foo} accepts arguments in registers 9 and 10: + +@smallexample +asm ("movl %0,r9\n\tmovl %1,r10\n\tcall _foo" + : /* no outputs */ + : "g" (from), "g" (to) + : "r9", "r10"); +@end smallexample + +Unless an output operand has the @samp{&} constraint modifier, GCC +may allocate it in the same register as an unrelated input operand, on +the assumption the inputs are consumed before the outputs are produced. +This assumption may be false if the assembler code actually consists of +more than one instruction. In such a case, use @samp{&} for each output +operand that may not overlap an input. @xref{Modifiers}. + +If you want to test the condition code produced by an assembler +instruction, you must include a branch and a label in the @code{asm} +construct, as follows: + +@smallexample +asm ("clr %0\n\tfrob %1\n\tbeq 0f\n\tmov #1,%0\n0:" + : "g" (result) + : "g" (input)); +@end smallexample + +@noindent +This assumes your assembler supports local labels, as the GNU assembler +and most Unix assemblers do. + +Speaking of labels, jumps from one @code{asm} to another are not +supported. The compiler's optimizers do not know about these jumps, and +therefore they cannot take account of them when deciding how to +optimize. @xref{Extended asm with goto}. + +@cindex macros containing @code{asm} +Usually the most convenient way to use these @code{asm} instructions is to +encapsulate them in macros that look like functions. For example, + +@smallexample +#define sin(x) \ +(@{ double __value, __arg = (x); \ + asm ("fsinx %1,%0": "=f" (__value): "f" (__arg)); \ + __value; @}) +@end smallexample + +@noindent +Here the variable @code{__arg} is used to make sure that the instruction +operates on a proper @code{double} value, and to accept only those +arguments @code{x} which can convert automatically to a @code{double}. + +Another way to make sure the instruction operates on the correct data +type is to use a cast in the @code{asm}. This is different from using a +variable @code{__arg} in that it converts more different types. For +example, if the desired type were @code{int}, casting the argument to +@code{int} would accept a pointer with no complaint, while assigning the +argument to an @code{int} variable named @code{__arg} would warn about +using a pointer unless the caller explicitly casts it. + +If an @code{asm} has output operands, GCC assumes for optimization +purposes the instruction has no side effects except to change the output +operands. This does not mean instructions with a side effect cannot be +used, but you must be careful, because the compiler may eliminate them +if the output operands aren't used, or move them out of loops, or +replace two with one if they constitute a common subexpression. Also, +if your instruction does have a side effect on a variable that otherwise +appears not to change, the old value of the variable may be reused later +if it happens to be found in a register. + +You can prevent an @code{asm} instruction from being deleted +by writing the keyword @code{volatile} after +the @code{asm}. For example: + +@smallexample +#define get_and_set_priority(new) \ +(@{ int __old; \ + asm volatile ("get_and_set_priority %0, %1" \ + : "=g" (__old) : "g" (new)); \ + __old; @}) +@end smallexample + +@noindent +The @code{volatile} keyword indicates that the instruction has +important side-effects. GCC will not delete a volatile @code{asm} if +it is reachable. (The instruction can still be deleted if GCC can +prove that control-flow will never reach the location of the +instruction.) Note that even a volatile @code{asm} instruction +can be moved relative to other code, including across jump +instructions. For example, on many targets there is a system +register which can be set to control the rounding mode of +floating point operations. You might try +setting it with a volatile @code{asm}, like this PowerPC example: + +@smallexample + asm volatile("mtfsf 255,%0" : : "f" (fpenv)); + sum = x + y; +@end smallexample + +@noindent +This will not work reliably, as the compiler may move the addition back +before the volatile @code{asm}. To make it work you need to add an +artificial dependency to the @code{asm} referencing a variable in the code +you don't want moved, for example: + +@smallexample + asm volatile ("mtfsf 255,%1" : "=X"(sum): "f"(fpenv)); + sum = x + y; +@end smallexample + +Similarly, you can't expect a +sequence of volatile @code{asm} instructions to remain perfectly +consecutive. If you want consecutive output, use a single @code{asm}. +Also, GCC will perform some optimizations across a volatile @code{asm} +instruction; GCC does not ``forget everything'' when it encounters +a volatile @code{asm} instruction the way some other compilers do. + +An @code{asm} instruction without any output operands will be treated +identically to a volatile @code{asm} instruction. + +It is a natural idea to look for a way to give access to the condition +code left by the assembler instruction. However, when we attempted to +implement this, we found no way to make it work reliably. The problem +is that output operands might need reloading, which would result in +additional following ``store'' instructions. On most machines, these +instructions would alter the condition code before there was time to +test it. This problem doesn't arise for ordinary ``test'' and +``compare'' instructions because they don't have any output operands. + +For reasons similar to those described above, it is not possible to give +an assembler instruction access to the condition code left by previous +instructions. + +@anchor{Extended asm with goto} +As of GCC version 4.5, @code{asm goto} may be used to have the assembly +jump to one or more C labels. In this form, a fifth section after the +clobber list contains a list of all C labels to which the assembly may jump. +Each label operand is implicitly self-named. The @code{asm} is also assumed +to fall through to the next statement. + +This form of @code{asm} is restricted to not have outputs. This is due +to a internal restriction in the compiler that control transfer instructions +cannot have outputs. This restriction on @code{asm goto} may be lifted +in some future version of the compiler. In the mean time, @code{asm goto} +may include a memory clobber, and so leave outputs in memory. + +@smallexample +int frob(int x) +@{ + int y; + asm goto ("frob %%r5, %1; jc %l[error]; mov (%2), %%r5" + : : "r"(x), "r"(&y) : "r5", "memory" : error); + return y; + error: + return -1; +@} +@end smallexample + +In this (inefficient) example, the @code{frob} instruction sets the +carry bit to indicate an error. The @code{jc} instruction detects +this and branches to the @code{error} label. Finally, the output +of the @code{frob} instruction (@code{%r5}) is stored into the memory +for variable @code{y}, which is later read by the @code{return} statement. + +@smallexample +void doit(void) +@{ + int i = 0; + asm goto ("mfsr %%r1, 123; jmp %%r1;" + ".pushsection doit_table;" + ".long %l0, %l1, %l2, %l3;" + ".popsection" + : : : "r1" : label1, label2, label3, label4); + __builtin_unreachable (); + + label1: + f1(); + return; + label2: + f2(); + return; + label3: + i = 1; + label4: + f3(i); +@} +@end smallexample + +In this (also inefficient) example, the @code{mfsr} instruction reads +an address from some out-of-band machine register, and the following +@code{jmp} instruction branches to that address. The address read by +the @code{mfsr} instruction is assumed to have been previously set via +some application-specific mechanism to be one of the four values stored +in the @code{doit_table} section. Finally, the @code{asm} is followed +by a call to @code{__builtin_unreachable} to indicate that the @code{asm} +does not in fact fall through. + +@smallexample +#define TRACE1(NUM) \ + do @{ \ + asm goto ("0: nop;" \ + ".pushsection trace_table;" \ + ".long 0b, %l0;" \ + ".popsection" \ + : : : : trace#NUM); \ + if (0) @{ trace#NUM: trace(); @} \ + @} while (0) +#define TRACE TRACE1(__COUNTER__) +@end smallexample + +In this example (which in fact inspired the @code{asm goto} feature) +we want on rare occasions to call the @code{trace} function; on other +occasions we'd like to keep the overhead to the absolute minimum. +The normal code path consists of a single @code{nop} instruction. +However, we record the address of this @code{nop} together with the +address of a label that calls the @code{trace} function. This allows +the @code{nop} instruction to be patched at runtime to be an +unconditional branch to the stored label. It is assumed that an +optimizing compiler will move the labeled block out of line, to +optimize the fall through path from the @code{asm}. + +If you are writing a header file that should be includable in ISO C +programs, write @code{__asm__} instead of @code{asm}. @xref{Alternate +Keywords}. + +@subsection Size of an @code{asm} + +Some targets require that GCC track the size of each instruction used in +order to generate correct code. Because the final length of an +@code{asm} is only known by the assembler, GCC must make an estimate as +to how big it will be. The estimate is formed by counting the number of +statements in the pattern of the @code{asm} and multiplying that by the +length of the longest instruction on that processor. Statements in the +@code{asm} are identified by newline characters and whatever statement +separator characters are supported by the assembler; on most processors +this is the `@code{;}' character. + +Normally, GCC's estimate is perfectly adequate to ensure that correct +code is generated, but it is possible to confuse the compiler if you use +pseudo instructions or assembler macros that expand into multiple real +instructions or if you use assembler directives that expand to more +space in the object file than would be needed for a single instruction. +If this happens then the assembler will produce a diagnostic saying that +a label is unreachable. + +@subsection i386 floating point asm operands + +There are several rules on the usage of stack-like regs in +asm_operands insns. These rules apply only to the operands that are +stack-like regs: + +@enumerate +@item +Given a set of input regs that die in an asm_operands, it is +necessary to know which are implicitly popped by the asm, and +which must be explicitly popped by gcc. + +An input reg that is implicitly popped by the asm must be +explicitly clobbered, unless it is constrained to match an +output operand. + +@item +For any input reg that is implicitly popped by an asm, it is +necessary to know how to adjust the stack to compensate for the pop. +If any non-popped input is closer to the top of the reg-stack than +the implicitly popped reg, it would not be possible to know what the +stack looked like---it's not clear how the rest of the stack ``slides +up''. + +All implicitly popped input regs must be closer to the top of +the reg-stack than any input that is not implicitly popped. + +It is possible that if an input dies in an insn, reload might +use the input reg for an output reload. Consider this example: + +@smallexample +asm ("foo" : "=t" (a) : "f" (b)); +@end smallexample + +This asm says that input B is not popped by the asm, and that +the asm pushes a result onto the reg-stack, i.e., the stack is one +deeper after the asm than it was before. But, it is possible that +reload will think that it can use the same reg for both the input and +the output, if input B dies in this insn. + +If any input operand uses the @code{f} constraint, all output reg +constraints must use the @code{&} earlyclobber. + +The asm above would be written as + +@smallexample +asm ("foo" : "=&t" (a) : "f" (b)); +@end smallexample + +@item +Some operands need to be in particular places on the stack. All +output operands fall in this category---there is no other way to +know which regs the outputs appear in unless the user indicates +this in the constraints. + +Output operands must specifically indicate which reg an output +appears in after an asm. @code{=f} is not allowed: the operand +constraints must select a class with a single reg. + +@item +Output operands may not be ``inserted'' between existing stack regs. +Since no 387 opcode uses a read/write operand, all output operands +are dead before the asm_operands, and are pushed by the asm_operands. +It makes no sense to push anywhere but the top of the reg-stack. + +Output operands must start at the top of the reg-stack: output +operands may not ``skip'' a reg. + +@item +Some asm statements may need extra stack space for internal +calculations. This can be guaranteed by clobbering stack registers +unrelated to the inputs and outputs. + +@end enumerate + +Here are a couple of reasonable asms to want to write. This asm +takes one input, which is internally popped, and produces two outputs. + +@smallexample +asm ("fsincos" : "=t" (cos), "=u" (sin) : "0" (inp)); +@end smallexample + +This asm takes two inputs, which are popped by the @code{fyl2xp1} opcode, +and replaces them with one output. The user must code the @code{st(1)} +clobber for reg-stack.c to know that @code{fyl2xp1} pops both inputs. + +@smallexample +asm ("fyl2xp1" : "=t" (result) : "0" (x), "u" (y) : "st(1)"); +@end smallexample + +@include md.texi + +@node Asm Labels +@section Controlling Names Used in Assembler Code +@cindex assembler names for identifiers +@cindex names used in assembler code +@cindex identifiers, names in assembler code + +You can specify the name to be used in the assembler code for a C +function or variable by writing the @code{asm} (or @code{__asm__}) +keyword after the declarator as follows: + +@smallexample +int foo asm ("myfoo") = 2; +@end smallexample + +@noindent +This specifies that the name to be used for the variable @code{foo} in +the assembler code should be @samp{myfoo} rather than the usual +@samp{_foo}. + +On systems where an underscore is normally prepended to the name of a C +function or variable, this feature allows you to define names for the +linker that do not start with an underscore. + +It does not make sense to use this feature with a non-static local +variable since such variables do not have assembler names. If you are +trying to put the variable in a particular register, see @ref{Explicit +Reg Vars}. GCC presently accepts such code with a warning, but will +probably be changed to issue an error, rather than a warning, in the +future. + +You cannot use @code{asm} in this way in a function @emph{definition}; but +you can get the same effect by writing a declaration for the function +before its definition and putting @code{asm} there, like this: + +@smallexample +extern func () asm ("FUNC"); + +func (x, y) + int x, y; +/* @r{@dots{}} */ +@end smallexample + +It is up to you to make sure that the assembler names you choose do not +conflict with any other assembler symbols. Also, you must not use a +register name; that would produce completely invalid assembler code. GCC +does not as yet have the ability to store static variables in registers. +Perhaps that will be added. + +@node Explicit Reg Vars +@section Variables in Specified Registers +@cindex explicit register variables +@cindex variables in specified registers +@cindex specified registers +@cindex registers, global allocation + +GNU C allows you to put a few global variables into specified hardware +registers. You can also specify the register in which an ordinary +register variable should be allocated. + +@itemize @bullet +@item +Global register variables reserve registers throughout the program. +This may be useful in programs such as programming language +interpreters which have a couple of global variables that are accessed +very often. + +@item +Local register variables in specific registers do not reserve the +registers, except at the point where they are used as input or output +operands in an @code{asm} statement and the @code{asm} statement itself is +not deleted. The compiler's data flow analysis is capable of determining +where the specified registers contain live values, and where they are +available for other uses. Stores into local register variables may be deleted +when they appear to be dead according to dataflow analysis. References +to local register variables may be deleted or moved or simplified. + +These local variables are sometimes convenient for use with the extended +@code{asm} feature (@pxref{Extended Asm}), if you want to write one +output of the assembler instruction directly into a particular register. +(This will work provided the register you specify fits the constraints +specified for that operand in the @code{asm}.) +@end itemize + +@menu +* Global Reg Vars:: +* Local Reg Vars:: +@end menu + +@node Global Reg Vars +@subsection Defining Global Register Variables +@cindex global register variables +@cindex registers, global variables in + +You can define a global register variable in GNU C like this: + +@smallexample +register int *foo asm ("a5"); +@end smallexample + +@noindent +Here @code{a5} is the name of the register which should be used. Choose a +register which is normally saved and restored by function calls on your +machine, so that library routines will not clobber it. + +Naturally the register name is cpu-dependent, so you would need to +conditionalize your program according to cpu type. The register +@code{a5} would be a good choice on a 68000 for a variable of pointer +type. On machines with register windows, be sure to choose a ``global'' +register that is not affected magically by the function call mechanism. + +In addition, operating systems on one type of cpu may differ in how they +name the registers; then you would need additional conditionals. For +example, some 68000 operating systems call this register @code{%a5}. + +Eventually there may be a way of asking the compiler to choose a register +automatically, but first we need to figure out how it should choose and +how to enable you to guide the choice. No solution is evident. + +Defining a global register variable in a certain register reserves that +register entirely for this use, at least within the current compilation. +The register will not be allocated for any other purpose in the functions +in the current compilation. The register will not be saved and restored by +these functions. Stores into this register are never deleted even if they +would appear to be dead, but references may be deleted or moved or +simplified. + +It is not safe to access the global register variables from signal +handlers, or from more than one thread of control, because the system +library routines may temporarily use the register for other things (unless +you recompile them specially for the task at hand). + +@cindex @code{qsort}, and global register variables +It is not safe for one function that uses a global register variable to +call another such function @code{foo} by way of a third function +@code{lose} that was compiled without knowledge of this variable (i.e.@: in a +different source file in which the variable wasn't declared). This is +because @code{lose} might save the register and put some other value there. +For example, you can't expect a global register variable to be available in +the comparison-function that you pass to @code{qsort}, since @code{qsort} +might have put something else in that register. (If you are prepared to +recompile @code{qsort} with the same global register variable, you can +solve this problem.) + +If you want to recompile @code{qsort} or other source files which do not +actually use your global register variable, so that they will not use that +register for any other purpose, then it suffices to specify the compiler +option @option{-ffixed-@var{reg}}. You need not actually add a global +register declaration to their source code. + +A function which can alter the value of a global register variable cannot +safely be called from a function compiled without this variable, because it +could clobber the value the caller expects to find there on return. +Therefore, the function which is the entry point into the part of the +program that uses the global register variable must explicitly save and +restore the value which belongs to its caller. + +@cindex register variable after @code{longjmp} +@cindex global register after @code{longjmp} +@cindex value after @code{longjmp} +@findex longjmp +@findex setjmp +On most machines, @code{longjmp} will restore to each global register +variable the value it had at the time of the @code{setjmp}. On some +machines, however, @code{longjmp} will not change the value of global +register variables. To be portable, the function that called @code{setjmp} +should make other arrangements to save the values of the global register +variables, and to restore them in a @code{longjmp}. This way, the same +thing will happen regardless of what @code{longjmp} does. + +All global register variable declarations must precede all function +definitions. If such a declaration could appear after function +definitions, the declaration would be too late to prevent the register from +being used for other purposes in the preceding functions. + +Global register variables may not have initial values, because an +executable file has no means to supply initial contents for a register. + +On the SPARC, there are reports that g3 @dots{} g7 are suitable +registers, but certain library functions, such as @code{getwd}, as well +as the subroutines for division and remainder, modify g3 and g4. g1 and +g2 are local temporaries. + +On the 68000, a2 @dots{} a5 should be suitable, as should d2 @dots{} d7. +Of course, it will not do to use more than a few of those. + +@node Local Reg Vars +@subsection Specifying Registers for Local Variables +@cindex local variables, specifying registers +@cindex specifying registers for local variables +@cindex registers for local variables + +You can define a local register variable with a specified register +like this: + +@smallexample +register int *foo asm ("a5"); +@end smallexample + +@noindent +Here @code{a5} is the name of the register which should be used. Note +that this is the same syntax used for defining global register +variables, but for a local variable it would appear within a function. + +Naturally the register name is cpu-dependent, but this is not a +problem, since specific registers are most often useful with explicit +assembler instructions (@pxref{Extended Asm}). Both of these things +generally require that you conditionalize your program according to +cpu type. + +In addition, operating systems on one type of cpu may differ in how they +name the registers; then you would need additional conditionals. For +example, some 68000 operating systems call this register @code{%a5}. + +Defining such a register variable does not reserve the register; it +remains available for other uses in places where flow control determines +the variable's value is not live. + +This option does not guarantee that GCC will generate code that has +this variable in the register you specify at all times. You may not +code an explicit reference to this register in the @emph{assembler +instruction template} part of an @code{asm} statement and assume it will +always refer to this variable. However, using the variable as an +@code{asm} @emph{operand} guarantees that the specified register is used +for the operand. + +Stores into local register variables may be deleted when they appear to be dead +according to dataflow analysis. References to local register variables may +be deleted or moved or simplified. + +As for global register variables, it's recommended that you choose a +register which is normally saved and restored by function calls on +your machine, so that library routines will not clobber it. A common +pitfall is to initialize multiple call-clobbered registers with +arbitrary expressions, where a function call or library call for an +arithmetic operator will overwrite a register value from a previous +assignment, for example @code{r0} below: +@smallexample +register int *p1 asm ("r0") = @dots{}; +register int *p2 asm ("r1") = @dots{}; +@end smallexample +In those cases, a solution is to use a temporary variable for +each arbitrary expression. @xref{Example of asm with clobbered asm reg}. + +@node Alternate Keywords +@section Alternate Keywords +@cindex alternate keywords +@cindex keywords, alternate + +@option{-ansi} and the various @option{-std} options disable certain +keywords. This causes trouble when you want to use GNU C extensions, or +a general-purpose header file that should be usable by all programs, +including ISO C programs. The keywords @code{asm}, @code{typeof} and +@code{inline} are not available in programs compiled with +@option{-ansi} or @option{-std} (although @code{inline} can be used in a +program compiled with @option{-std=c99} or @option{-std=c1x}). The +ISO C99 keyword +@code{restrict} is only available when @option{-std=gnu99} (which will +eventually be the default) or @option{-std=c99} (or the equivalent +@option{-std=iso9899:1999}), or an option for a later standard +version, is used. + +The way to solve these problems is to put @samp{__} at the beginning and +end of each problematical keyword. For example, use @code{__asm__} +instead of @code{asm}, and @code{__inline__} instead of @code{inline}. + +Other C compilers won't accept these alternative keywords; if you want to +compile with another compiler, you can define the alternate keywords as +macros to replace them with the customary keywords. It looks like this: + +@smallexample +#ifndef __GNUC__ +#define __asm__ asm +#endif +@end smallexample + +@findex __extension__ +@opindex pedantic +@option{-pedantic} and other options cause warnings for many GNU C extensions. +You can +prevent such warnings within one expression by writing +@code{__extension__} before the expression. @code{__extension__} has no +effect aside from this. + +@node Incomplete Enums +@section Incomplete @code{enum} Types + +You can define an @code{enum} tag without specifying its possible values. +This results in an incomplete type, much like what you get if you write +@code{struct foo} without describing the elements. A later declaration +which does specify the possible values completes the type. + +You can't allocate variables or storage using the type while it is +incomplete. However, you can work with pointers to that type. + +This extension may not be very useful, but it makes the handling of +@code{enum} more consistent with the way @code{struct} and @code{union} +are handled. + +This extension is not supported by GNU C++. + +@node Function Names +@section Function Names as Strings +@cindex @code{__func__} identifier +@cindex @code{__FUNCTION__} identifier +@cindex @code{__PRETTY_FUNCTION__} identifier + +GCC provides three magic variables which hold the name of the current +function, as a string. The first of these is @code{__func__}, which +is part of the C99 standard: + +The identifier @code{__func__} is implicitly declared by the translator +as if, immediately following the opening brace of each function +definition, the declaration + +@smallexample +static const char __func__[] = "function-name"; +@end smallexample + +@noindent +appeared, where function-name is the name of the lexically-enclosing +function. This name is the unadorned name of the function. + +@code{__FUNCTION__} is another name for @code{__func__}. Older +versions of GCC recognize only this name. However, it is not +standardized. For maximum portability, we recommend you use +@code{__func__}, but provide a fallback definition with the +preprocessor: + +@smallexample +#if __STDC_VERSION__ < 199901L +# if __GNUC__ >= 2 +# define __func__ __FUNCTION__ +# else +# define __func__ "<unknown>" +# endif +#endif +@end smallexample + +In C, @code{__PRETTY_FUNCTION__} is yet another name for +@code{__func__}. However, in C++, @code{__PRETTY_FUNCTION__} contains +the type signature of the function as well as its bare name. For +example, this program: + +@smallexample +extern "C" @{ +extern int printf (char *, ...); +@} + +class a @{ + public: + void sub (int i) + @{ + printf ("__FUNCTION__ = %s\n", __FUNCTION__); + printf ("__PRETTY_FUNCTION__ = %s\n", __PRETTY_FUNCTION__); + @} +@}; + +int +main (void) +@{ + a ax; + ax.sub (0); + return 0; +@} +@end smallexample + +@noindent +gives this output: + +@smallexample +__FUNCTION__ = sub +__PRETTY_FUNCTION__ = void a::sub(int) +@end smallexample + +These identifiers are not preprocessor macros. In GCC 3.3 and +earlier, in C only, @code{__FUNCTION__} and @code{__PRETTY_FUNCTION__} +were treated as string literals; they could be used to initialize +@code{char} arrays, and they could be concatenated with other string +literals. GCC 3.4 and later treat them as variables, like +@code{__func__}. In C++, @code{__FUNCTION__} and +@code{__PRETTY_FUNCTION__} have always been variables. + +@node Return Address +@section Getting the Return or Frame Address of a Function + +These functions may be used to get information about the callers of a +function. + +@deftypefn {Built-in Function} {void *} __builtin_return_address (unsigned int @var{level}) +This function returns the return address of the current function, or of +one of its callers. The @var{level} argument is number of frames to +scan up the call stack. A value of @code{0} yields the return address +of the current function, a value of @code{1} yields the return address +of the caller of the current function, and so forth. When inlining +the expected behavior is that the function will return the address of +the function that will be returned to. To work around this behavior use +the @code{noinline} function attribute. + +The @var{level} argument must be a constant integer. + +On some machines it may be impossible to determine the return address of +any function other than the current one; in such cases, or when the top +of the stack has been reached, this function will return @code{0} or a +random value. In addition, @code{__builtin_frame_address} may be used +to determine if the top of the stack has been reached. + +Additional post-processing of the returned value may be needed, see +@code{__builtin_extract_return_address}. + +This function should only be used with a nonzero argument for debugging +purposes. +@end deftypefn + +@deftypefn {Built-in Function} {void *} __builtin_extract_return_address (void *@var{addr}) +The address as returned by @code{__builtin_return_address} may have to be fed +through this function to get the actual encoded address. For example, on the +31-bit S/390 platform the highest bit has to be masked out, or on SPARC +platforms an offset has to be added for the true next instruction to be +executed. + +If no fixup is needed, this function simply passes through @var{addr}. +@end deftypefn + +@deftypefn {Built-in Function} {void *} __builtin_frob_return_address (void *@var{addr}) +This function does the reverse of @code{__builtin_extract_return_address}. +@end deftypefn + +@deftypefn {Built-in Function} {void *} __builtin_frame_address (unsigned int @var{level}) +This function is similar to @code{__builtin_return_address}, but it +returns the address of the function frame rather than the return address +of the function. Calling @code{__builtin_frame_address} with a value of +@code{0} yields the frame address of the current function, a value of +@code{1} yields the frame address of the caller of the current function, +and so forth. + +The frame is the area on the stack which holds local variables and saved +registers. The frame address is normally the address of the first word +pushed on to the stack by the function. However, the exact definition +depends upon the processor and the calling convention. If the processor +has a dedicated frame pointer register, and the function has a frame, +then @code{__builtin_frame_address} will return the value of the frame +pointer register. + +On some machines it may be impossible to determine the frame address of +any function other than the current one; in such cases, or when the top +of the stack has been reached, this function will return @code{0} if +the first frame pointer is properly initialized by the startup code. + +This function should only be used with a nonzero argument for debugging +purposes. +@end deftypefn + +@node Vector Extensions +@section Using vector instructions through built-in functions + +On some targets, the instruction set contains SIMD vector instructions that +operate on multiple values contained in one large register at the same time. +For example, on the i386 the MMX, 3DNow!@: and SSE extensions can be used +this way. + +The first step in using these extensions is to provide the necessary data +types. This should be done using an appropriate @code{typedef}: + +@smallexample +typedef int v4si __attribute__ ((vector_size (16))); +@end smallexample + +The @code{int} type specifies the base type, while the attribute specifies +the vector size for the variable, measured in bytes. For example, the +declaration above causes the compiler to set the mode for the @code{v4si} +type to be 16 bytes wide and divided into @code{int} sized units. For +a 32-bit @code{int} this means a vector of 4 units of 4 bytes, and the +corresponding mode of @code{foo} will be @acronym{V4SI}. + +The @code{vector_size} attribute is only applicable to integral and +float scalars, although arrays, pointers, and function return values +are allowed in conjunction with this construct. + +All the basic integer types can be used as base types, both as signed +and as unsigned: @code{char}, @code{short}, @code{int}, @code{long}, +@code{long long}. In addition, @code{float} and @code{double} can be +used to build floating-point vector types. + +Specifying a combination that is not valid for the current architecture +will cause GCC to synthesize the instructions using a narrower mode. +For example, if you specify a variable of type @code{V4SI} and your +architecture does not allow for this specific SIMD type, GCC will +produce code that uses 4 @code{SIs}. + +The types defined in this manner can be used with a subset of normal C +operations. Currently, GCC will allow using the following operators +on these types: @code{+, -, *, /, unary minus, ^, |, &, ~, %}@. + +The operations behave like C++ @code{valarrays}. Addition is defined as +the addition of the corresponding elements of the operands. For +example, in the code below, each of the 4 elements in @var{a} will be +added to the corresponding 4 elements in @var{b} and the resulting +vector will be stored in @var{c}. + +@smallexample +typedef int v4si __attribute__ ((vector_size (16))); + +v4si a, b, c; + +c = a + b; +@end smallexample + +Subtraction, multiplication, division, and the logical operations +operate in a similar manner. Likewise, the result of using the unary +minus or complement operators on a vector type is a vector whose +elements are the negative or complemented values of the corresponding +elements in the operand. + +In C it is possible to use shifting operators @code{<<}, @code{>>} on +integer-type vectors. The operation is defined as following: @code{@{a0, +a1, @dots{}, an@} >> @{b0, b1, @dots{}, bn@} == @{a0 >> b0, a1 >> b1, +@dots{}, an >> bn@}}@. Vector operands must have the same number of +elements. Additionally second operands can be a scalar integer in which +case the scalar is converted to the type used by the vector operand (with +possible truncation) and each element of this new vector is the scalar's +value. +Consider the following code. + +@smallexample +typedef int v4si __attribute__ ((vector_size (16))); + +v4si a, b; + +b = a >> 1; /* b = a >> @{1,1,1,1@}; */ +@end smallexample + +In C vectors can be subscripted as if the vector were an array with +the same number of elements and base type. Out of bound accesses +invoke undefined behavior at runtime. Warnings for out of bound +accesses for vector subscription can be enabled with +@option{-Warray-bounds}. + +You can declare variables and use them in function calls and returns, as +well as in assignments and some casts. You can specify a vector type as +a return type for a function. Vector types can also be used as function +arguments. It is possible to cast from one vector type to another, +provided they are of the same size (in fact, you can also cast vectors +to and from other datatypes of the same size). + +You cannot operate between vectors of different lengths or different +signedness without a cast. + +A port that supports hardware vector operations, usually provides a set +of built-in functions that can be used to operate on vectors. For +example, a function to add two vectors and multiply the result by a +third could look like this: + +@smallexample +v4si f (v4si a, v4si b, v4si c) +@{ + v4si tmp = __builtin_addv4si (a, b); + return __builtin_mulv4si (tmp, c); +@} + +@end smallexample + +@node Offsetof +@section Offsetof +@findex __builtin_offsetof + +GCC implements for both C and C++ a syntactic extension to implement +the @code{offsetof} macro. + +@smallexample +primary: + "__builtin_offsetof" "(" @code{typename} "," offsetof_member_designator ")" + +offsetof_member_designator: + @code{identifier} + | offsetof_member_designator "." @code{identifier} + | offsetof_member_designator "[" @code{expr} "]" +@end smallexample + +This extension is sufficient such that + +@smallexample +#define offsetof(@var{type}, @var{member}) __builtin_offsetof (@var{type}, @var{member}) +@end smallexample + +is a suitable definition of the @code{offsetof} macro. In C++, @var{type} +may be dependent. In either case, @var{member} may consist of a single +identifier, or a sequence of member accesses and array references. + +@node Atomic Builtins +@section Built-in functions for atomic memory access + +The following builtins are intended to be compatible with those described +in the @cite{Intel Itanium Processor-specific Application Binary Interface}, +section 7.4. As such, they depart from the normal GCC practice of using +the ``__builtin_'' prefix, and further that they are overloaded such that +they work on multiple types. + +The definition given in the Intel documentation allows only for the use of +the types @code{int}, @code{long}, @code{long long} as well as their unsigned +counterparts. GCC will allow any integral scalar or pointer type that is +1, 2, 4 or 8 bytes in length. + +Not all operations are supported by all target processors. If a particular +operation cannot be implemented on the target processor, a warning will be +generated and a call an external function will be generated. The external +function will carry the same name as the builtin, with an additional suffix +@samp{_@var{n}} where @var{n} is the size of the data type. + +@c ??? Should we have a mechanism to suppress this warning? This is almost +@c useful for implementing the operation under the control of an external +@c mutex. + +In most cases, these builtins are considered a @dfn{full barrier}. That is, +no memory operand will be moved across the operation, either forward or +backward. Further, instructions will be issued as necessary to prevent the +processor from speculating loads across the operation and from queuing stores +after the operation. + +All of the routines are described in the Intel documentation to take +``an optional list of variables protected by the memory barrier''. It's +not clear what is meant by that; it could mean that @emph{only} the +following variables are protected, or it could mean that these variables +should in addition be protected. At present GCC ignores this list and +protects all variables which are globally accessible. If in the future +we make some use of this list, an empty list will continue to mean all +globally accessible variables. + +@table @code +@item @var{type} __sync_fetch_and_add (@var{type} *ptr, @var{type} value, ...) +@itemx @var{type} __sync_fetch_and_sub (@var{type} *ptr, @var{type} value, ...) +@itemx @var{type} __sync_fetch_and_or (@var{type} *ptr, @var{type} value, ...) +@itemx @var{type} __sync_fetch_and_and (@var{type} *ptr, @var{type} value, ...) +@itemx @var{type} __sync_fetch_and_xor (@var{type} *ptr, @var{type} value, ...) +@itemx @var{type} __sync_fetch_and_nand (@var{type} *ptr, @var{type} value, ...) +@findex __sync_fetch_and_add +@findex __sync_fetch_and_sub +@findex __sync_fetch_and_or +@findex __sync_fetch_and_and +@findex __sync_fetch_and_xor +@findex __sync_fetch_and_nand +These builtins perform the operation suggested by the name, and +returns the value that had previously been in memory. That is, + +@smallexample +@{ tmp = *ptr; *ptr @var{op}= value; return tmp; @} +@{ tmp = *ptr; *ptr = ~(tmp & value); return tmp; @} // nand +@end smallexample + +@emph{Note:} GCC 4.4 and later implement @code{__sync_fetch_and_nand} +builtin as @code{*ptr = ~(tmp & value)} instead of @code{*ptr = ~tmp & value}. + +@item @var{type} __sync_add_and_fetch (@var{type} *ptr, @var{type} value, ...) +@itemx @var{type} __sync_sub_and_fetch (@var{type} *ptr, @var{type} value, ...) +@itemx @var{type} __sync_or_and_fetch (@var{type} *ptr, @var{type} value, ...) +@itemx @var{type} __sync_and_and_fetch (@var{type} *ptr, @var{type} value, ...) +@itemx @var{type} __sync_xor_and_fetch (@var{type} *ptr, @var{type} value, ...) +@itemx @var{type} __sync_nand_and_fetch (@var{type} *ptr, @var{type} value, ...) +@findex __sync_add_and_fetch +@findex __sync_sub_and_fetch +@findex __sync_or_and_fetch +@findex __sync_and_and_fetch +@findex __sync_xor_and_fetch +@findex __sync_nand_and_fetch +These builtins perform the operation suggested by the name, and +return the new value. That is, + +@smallexample +@{ *ptr @var{op}= value; return *ptr; @} +@{ *ptr = ~(*ptr & value); return *ptr; @} // nand +@end smallexample + +@emph{Note:} GCC 4.4 and later implement @code{__sync_nand_and_fetch} +builtin as @code{*ptr = ~(*ptr & value)} instead of +@code{*ptr = ~*ptr & value}. + +@item bool __sync_bool_compare_and_swap (@var{type} *ptr, @var{type} oldval @var{type} newval, ...) +@itemx @var{type} __sync_val_compare_and_swap (@var{type} *ptr, @var{type} oldval @var{type} newval, ...) +@findex __sync_bool_compare_and_swap +@findex __sync_val_compare_and_swap +These builtins perform an atomic compare and swap. That is, if the current +value of @code{*@var{ptr}} is @var{oldval}, then write @var{newval} into +@code{*@var{ptr}}. + +The ``bool'' version returns true if the comparison is successful and +@var{newval} was written. The ``val'' version returns the contents +of @code{*@var{ptr}} before the operation. + +@item __sync_synchronize (...) +@findex __sync_synchronize +This builtin issues a full memory barrier. + +@item @var{type} __sync_lock_test_and_set (@var{type} *ptr, @var{type} value, ...) +@findex __sync_lock_test_and_set +This builtin, as described by Intel, is not a traditional test-and-set +operation, but rather an atomic exchange operation. It writes @var{value} +into @code{*@var{ptr}}, and returns the previous contents of +@code{*@var{ptr}}. + +Many targets have only minimal support for such locks, and do not support +a full exchange operation. In this case, a target may support reduced +functionality here by which the @emph{only} valid value to store is the +immediate constant 1. The exact value actually stored in @code{*@var{ptr}} +is implementation defined. + +This builtin is not a full barrier, but rather an @dfn{acquire barrier}. +This means that references after the builtin cannot move to (or be +speculated to) before the builtin, but previous memory stores may not +be globally visible yet, and previous memory loads may not yet be +satisfied. + +@item void __sync_lock_release (@var{type} *ptr, ...) +@findex __sync_lock_release +This builtin releases the lock acquired by @code{__sync_lock_test_and_set}. +Normally this means writing the constant 0 to @code{*@var{ptr}}. + +This builtin is not a full barrier, but rather a @dfn{release barrier}. +This means that all previous memory stores are globally visible, and all +previous memory loads have been satisfied, but following memory reads +are not prevented from being speculated to before the barrier. +@end table + +@node Object Size Checking +@section Object Size Checking Builtins +@findex __builtin_object_size +@findex __builtin___memcpy_chk +@findex __builtin___mempcpy_chk +@findex __builtin___memmove_chk +@findex __builtin___memset_chk +@findex __builtin___strcpy_chk +@findex __builtin___stpcpy_chk +@findex __builtin___strncpy_chk +@findex __builtin___strcat_chk +@findex __builtin___strncat_chk +@findex __builtin___sprintf_chk +@findex __builtin___snprintf_chk +@findex __builtin___vsprintf_chk +@findex __builtin___vsnprintf_chk +@findex __builtin___printf_chk +@findex __builtin___vprintf_chk +@findex __builtin___fprintf_chk +@findex __builtin___vfprintf_chk + +GCC implements a limited buffer overflow protection mechanism +that can prevent some buffer overflow attacks. + +@deftypefn {Built-in Function} {size_t} __builtin_object_size (void * @var{ptr}, int @var{type}) +is a built-in construct that returns a constant number of bytes from +@var{ptr} to the end of the object @var{ptr} pointer points to +(if known at compile time). @code{__builtin_object_size} never evaluates +its arguments for side-effects. If there are any side-effects in them, it +returns @code{(size_t) -1} for @var{type} 0 or 1 and @code{(size_t) 0} +for @var{type} 2 or 3. If there are multiple objects @var{ptr} can +point to and all of them are known at compile time, the returned number +is the maximum of remaining byte counts in those objects if @var{type} & 2 is +0 and minimum if nonzero. If it is not possible to determine which objects +@var{ptr} points to at compile time, @code{__builtin_object_size} should +return @code{(size_t) -1} for @var{type} 0 or 1 and @code{(size_t) 0} +for @var{type} 2 or 3. + +@var{type} is an integer constant from 0 to 3. If the least significant +bit is clear, objects are whole variables, if it is set, a closest +surrounding subobject is considered the object a pointer points to. +The second bit determines if maximum or minimum of remaining bytes +is computed. + +@smallexample +struct V @{ char buf1[10]; int b; char buf2[10]; @} var; +char *p = &var.buf1[1], *q = &var.b; + +/* Here the object p points to is var. */ +assert (__builtin_object_size (p, 0) == sizeof (var) - 1); +/* The subobject p points to is var.buf1. */ +assert (__builtin_object_size (p, 1) == sizeof (var.buf1) - 1); +/* The object q points to is var. */ +assert (__builtin_object_size (q, 0) + == (char *) (&var + 1) - (char *) &var.b); +/* The subobject q points to is var.b. */ +assert (__builtin_object_size (q, 1) == sizeof (var.b)); +@end smallexample +@end deftypefn + +There are built-in functions added for many common string operation +functions, e.g., for @code{memcpy} @code{__builtin___memcpy_chk} +built-in is provided. This built-in has an additional last argument, +which is the number of bytes remaining in object the @var{dest} +argument points to or @code{(size_t) -1} if the size is not known. + +The built-in functions are optimized into the normal string functions +like @code{memcpy} if the last argument is @code{(size_t) -1} or if +it is known at compile time that the destination object will not +be overflown. If the compiler can determine at compile time the +object will be always overflown, it issues a warning. + +The intended use can be e.g. + +@smallexample +#undef memcpy +#define bos0(dest) __builtin_object_size (dest, 0) +#define memcpy(dest, src, n) \ + __builtin___memcpy_chk (dest, src, n, bos0 (dest)) + +char *volatile p; +char buf[10]; +/* It is unknown what object p points to, so this is optimized + into plain memcpy - no checking is possible. */ +memcpy (p, "abcde", n); +/* Destination is known and length too. It is known at compile + time there will be no overflow. */ +memcpy (&buf[5], "abcde", 5); +/* Destination is known, but the length is not known at compile time. + This will result in __memcpy_chk call that can check for overflow + at runtime. */ +memcpy (&buf[5], "abcde", n); +/* Destination is known and it is known at compile time there will + be overflow. There will be a warning and __memcpy_chk call that + will abort the program at runtime. */ +memcpy (&buf[6], "abcde", 5); +@end smallexample + +Such built-in functions are provided for @code{memcpy}, @code{mempcpy}, +@code{memmove}, @code{memset}, @code{strcpy}, @code{stpcpy}, @code{strncpy}, +@code{strcat} and @code{strncat}. + +There are also checking built-in functions for formatted output functions. +@smallexample +int __builtin___sprintf_chk (char *s, int flag, size_t os, const char *fmt, ...); +int __builtin___snprintf_chk (char *s, size_t maxlen, int flag, size_t os, + const char *fmt, ...); +int __builtin___vsprintf_chk (char *s, int flag, size_t os, const char *fmt, + va_list ap); +int __builtin___vsnprintf_chk (char *s, size_t maxlen, int flag, size_t os, + const char *fmt, va_list ap); +@end smallexample + +The added @var{flag} argument is passed unchanged to @code{__sprintf_chk} +etc.@: functions and can contain implementation specific flags on what +additional security measures the checking function might take, such as +handling @code{%n} differently. + +The @var{os} argument is the object size @var{s} points to, like in the +other built-in functions. There is a small difference in the behavior +though, if @var{os} is @code{(size_t) -1}, the built-in functions are +optimized into the non-checking functions only if @var{flag} is 0, otherwise +the checking function is called with @var{os} argument set to +@code{(size_t) -1}. + +In addition to this, there are checking built-in functions +@code{__builtin___printf_chk}, @code{__builtin___vprintf_chk}, +@code{__builtin___fprintf_chk} and @code{__builtin___vfprintf_chk}. +These have just one additional argument, @var{flag}, right before +format string @var{fmt}. If the compiler is able to optimize them to +@code{fputc} etc.@: functions, it will, otherwise the checking function +should be called and the @var{flag} argument passed to it. + +@node Other Builtins +@section Other built-in functions provided by GCC +@cindex built-in functions +@findex __builtin_fpclassify +@findex __builtin_isfinite +@findex __builtin_isnormal +@findex __builtin_isgreater +@findex __builtin_isgreaterequal +@findex __builtin_isinf_sign +@findex __builtin_isless +@findex __builtin_islessequal +@findex __builtin_islessgreater +@findex __builtin_isunordered +@findex __builtin_powi +@findex __builtin_powif +@findex __builtin_powil +@findex _Exit +@findex _exit +@findex abort +@findex abs +@findex acos +@findex acosf +@findex acosh +@findex acoshf +@findex acoshl +@findex acosl +@findex alloca +@findex asin +@findex asinf +@findex asinh +@findex asinhf +@findex asinhl +@findex asinl +@findex atan +@findex atan2 +@findex atan2f +@findex atan2l +@findex atanf +@findex atanh +@findex atanhf +@findex atanhl +@findex atanl +@findex bcmp +@findex bzero +@findex cabs +@findex cabsf +@findex cabsl +@findex cacos +@findex cacosf +@findex cacosh +@findex cacoshf +@findex cacoshl +@findex cacosl +@findex calloc +@findex carg +@findex cargf +@findex cargl +@findex casin +@findex casinf +@findex casinh +@findex casinhf +@findex casinhl +@findex casinl +@findex catan +@findex catanf +@findex catanh +@findex catanhf +@findex catanhl +@findex catanl +@findex cbrt +@findex cbrtf +@findex cbrtl +@findex ccos +@findex ccosf +@findex ccosh +@findex ccoshf +@findex ccoshl +@findex ccosl +@findex ceil +@findex ceilf +@findex ceill +@findex cexp +@findex cexpf +@findex cexpl +@findex cimag +@findex cimagf +@findex cimagl +@findex clog +@findex clogf +@findex clogl +@findex conj +@findex conjf +@findex conjl +@findex copysign +@findex copysignf +@findex copysignl +@findex cos +@findex cosf +@findex cosh +@findex coshf +@findex coshl +@findex cosl +@findex cpow +@findex cpowf +@findex cpowl +@findex cproj +@findex cprojf +@findex cprojl +@findex creal +@findex crealf +@findex creall +@findex csin +@findex csinf +@findex csinh +@findex csinhf +@findex csinhl +@findex csinl +@findex csqrt +@findex csqrtf +@findex csqrtl +@findex ctan +@findex ctanf +@findex ctanh +@findex ctanhf +@findex ctanhl +@findex ctanl +@findex dcgettext +@findex dgettext +@findex drem +@findex dremf +@findex dreml +@findex erf +@findex erfc +@findex erfcf +@findex erfcl +@findex erff +@findex erfl +@findex exit +@findex exp +@findex exp10 +@findex exp10f +@findex exp10l +@findex exp2 +@findex exp2f +@findex exp2l +@findex expf +@findex expl +@findex expm1 +@findex expm1f +@findex expm1l +@findex fabs +@findex fabsf +@findex fabsl +@findex fdim +@findex fdimf +@findex fdiml +@findex ffs +@findex floor +@findex floorf +@findex floorl +@findex fma +@findex fmaf +@findex fmal +@findex fmax +@findex fmaxf +@findex fmaxl +@findex fmin +@findex fminf +@findex fminl +@findex fmod +@findex fmodf +@findex fmodl +@findex fprintf +@findex fprintf_unlocked +@findex fputs +@findex fputs_unlocked +@findex frexp +@findex frexpf +@findex frexpl +@findex fscanf +@findex gamma +@findex gammaf +@findex gammal +@findex gamma_r +@findex gammaf_r +@findex gammal_r +@findex gettext +@findex hypot +@findex hypotf +@findex hypotl +@findex ilogb +@findex ilogbf +@findex ilogbl +@findex imaxabs +@findex index +@findex isalnum +@findex isalpha +@findex isascii +@findex isblank +@findex iscntrl +@findex isdigit +@findex isgraph +@findex islower +@findex isprint +@findex ispunct +@findex isspace +@findex isupper +@findex iswalnum +@findex iswalpha +@findex iswblank +@findex iswcntrl +@findex iswdigit +@findex iswgraph +@findex iswlower +@findex iswprint +@findex iswpunct +@findex iswspace +@findex iswupper +@findex iswxdigit +@findex isxdigit +@findex j0 +@findex j0f +@findex j0l +@findex j1 +@findex j1f +@findex j1l +@findex jn +@findex jnf +@findex jnl +@findex labs +@findex ldexp +@findex ldexpf +@findex ldexpl +@findex lgamma +@findex lgammaf +@findex lgammal +@findex lgamma_r +@findex lgammaf_r +@findex lgammal_r +@findex llabs +@findex llrint +@findex llrintf +@findex llrintl +@findex llround +@findex llroundf +@findex llroundl +@findex log +@findex log10 +@findex log10f +@findex log10l +@findex log1p +@findex log1pf +@findex log1pl +@findex log2 +@findex log2f +@findex log2l +@findex logb +@findex logbf +@findex logbl +@findex logf +@findex logl +@findex lrint +@findex lrintf +@findex lrintl +@findex lround +@findex lroundf +@findex lroundl +@findex malloc +@findex memchr +@findex memcmp +@findex memcpy +@findex mempcpy +@findex memset +@findex modf +@findex modff +@findex modfl +@findex nearbyint +@findex nearbyintf +@findex nearbyintl +@findex nextafter +@findex nextafterf +@findex nextafterl +@findex nexttoward +@findex nexttowardf +@findex nexttowardl +@findex pow +@findex pow10 +@findex pow10f +@findex pow10l +@findex powf +@findex powl +@findex printf +@findex printf_unlocked +@findex putchar +@findex puts +@findex remainder +@findex remainderf +@findex remainderl +@findex remquo +@findex remquof +@findex remquol +@findex rindex +@findex rint +@findex rintf +@findex rintl +@findex round +@findex roundf +@findex roundl +@findex scalb +@findex scalbf +@findex scalbl +@findex scalbln +@findex scalblnf +@findex scalblnf +@findex scalbn +@findex scalbnf +@findex scanfnl +@findex signbit +@findex signbitf +@findex signbitl +@findex signbitd32 +@findex signbitd64 +@findex signbitd128 +@findex significand +@findex significandf +@findex significandl +@findex sin +@findex sincos +@findex sincosf +@findex sincosl +@findex sinf +@findex sinh +@findex sinhf +@findex sinhl +@findex sinl +@findex snprintf +@findex sprintf +@findex sqrt +@findex sqrtf +@findex sqrtl +@findex sscanf +@findex stpcpy +@findex stpncpy +@findex strcasecmp +@findex strcat +@findex strchr +@findex strcmp +@findex strcpy +@findex strcspn +@findex strdup +@findex strfmon +@findex strftime +@findex strlen +@findex strncasecmp +@findex strncat +@findex strncmp +@findex strncpy +@findex strndup +@findex strpbrk +@findex strrchr +@findex strspn +@findex strstr +@findex tan +@findex tanf +@findex tanh +@findex tanhf +@findex tanhl +@findex tanl +@findex tgamma +@findex tgammaf +@findex tgammal +@findex toascii +@findex tolower +@findex toupper +@findex towlower +@findex towupper +@findex trunc +@findex truncf +@findex truncl +@findex vfprintf +@findex vfscanf +@findex vprintf +@findex vscanf +@findex vsnprintf +@findex vsprintf +@findex vsscanf +@findex y0 +@findex y0f +@findex y0l +@findex y1 +@findex y1f +@findex y1l +@findex yn +@findex ynf +@findex ynl + +GCC provides a large number of built-in functions other than the ones +mentioned above. Some of these are for internal use in the processing +of exceptions or variable-length argument lists and will not be +documented here because they may change from time to time; we do not +recommend general use of these functions. + +The remaining functions are provided for optimization purposes. + +@opindex fno-builtin +GCC includes built-in versions of many of the functions in the standard +C library. The versions prefixed with @code{__builtin_} will always be +treated as having the same meaning as the C library function even if you +specify the @option{-fno-builtin} option. (@pxref{C Dialect Options}) +Many of these functions are only optimized in certain cases; if they are +not optimized in a particular case, a call to the library function will +be emitted. + +@opindex ansi +@opindex std +Outside strict ISO C mode (@option{-ansi}, @option{-std=c90}, +@option{-std=c99} or @option{-std=c1x}), the functions +@code{_exit}, @code{alloca}, @code{bcmp}, @code{bzero}, +@code{dcgettext}, @code{dgettext}, @code{dremf}, @code{dreml}, +@code{drem}, @code{exp10f}, @code{exp10l}, @code{exp10}, @code{ffsll}, +@code{ffsl}, @code{ffs}, @code{fprintf_unlocked}, +@code{fputs_unlocked}, @code{gammaf}, @code{gammal}, @code{gamma}, +@code{gammaf_r}, @code{gammal_r}, @code{gamma_r}, @code{gettext}, +@code{index}, @code{isascii}, @code{j0f}, @code{j0l}, @code{j0}, +@code{j1f}, @code{j1l}, @code{j1}, @code{jnf}, @code{jnl}, @code{jn}, +@code{lgammaf_r}, @code{lgammal_r}, @code{lgamma_r}, @code{mempcpy}, +@code{pow10f}, @code{pow10l}, @code{pow10}, @code{printf_unlocked}, +@code{rindex}, @code{scalbf}, @code{scalbl}, @code{scalb}, +@code{signbit}, @code{signbitf}, @code{signbitl}, @code{signbitd32}, +@code{signbitd64}, @code{signbitd128}, @code{significandf}, +@code{significandl}, @code{significand}, @code{sincosf}, +@code{sincosl}, @code{sincos}, @code{stpcpy}, @code{stpncpy}, +@code{strcasecmp}, @code{strdup}, @code{strfmon}, @code{strncasecmp}, +@code{strndup}, @code{toascii}, @code{y0f}, @code{y0l}, @code{y0}, +@code{y1f}, @code{y1l}, @code{y1}, @code{ynf}, @code{ynl} and +@code{yn} +may be handled as built-in functions. +All these functions have corresponding versions +prefixed with @code{__builtin_}, which may be used even in strict C90 +mode. + +The ISO C99 functions +@code{_Exit}, @code{acoshf}, @code{acoshl}, @code{acosh}, @code{asinhf}, +@code{asinhl}, @code{asinh}, @code{atanhf}, @code{atanhl}, @code{atanh}, +@code{cabsf}, @code{cabsl}, @code{cabs}, @code{cacosf}, @code{cacoshf}, +@code{cacoshl}, @code{cacosh}, @code{cacosl}, @code{cacos}, +@code{cargf}, @code{cargl}, @code{carg}, @code{casinf}, @code{casinhf}, +@code{casinhl}, @code{casinh}, @code{casinl}, @code{casin}, +@code{catanf}, @code{catanhf}, @code{catanhl}, @code{catanh}, +@code{catanl}, @code{catan}, @code{cbrtf}, @code{cbrtl}, @code{cbrt}, +@code{ccosf}, @code{ccoshf}, @code{ccoshl}, @code{ccosh}, @code{ccosl}, +@code{ccos}, @code{cexpf}, @code{cexpl}, @code{cexp}, @code{cimagf}, +@code{cimagl}, @code{cimag}, @code{clogf}, @code{clogl}, @code{clog}, +@code{conjf}, @code{conjl}, @code{conj}, @code{copysignf}, @code{copysignl}, +@code{copysign}, @code{cpowf}, @code{cpowl}, @code{cpow}, @code{cprojf}, +@code{cprojl}, @code{cproj}, @code{crealf}, @code{creall}, @code{creal}, +@code{csinf}, @code{csinhf}, @code{csinhl}, @code{csinh}, @code{csinl}, +@code{csin}, @code{csqrtf}, @code{csqrtl}, @code{csqrt}, @code{ctanf}, +@code{ctanhf}, @code{ctanhl}, @code{ctanh}, @code{ctanl}, @code{ctan}, +@code{erfcf}, @code{erfcl}, @code{erfc}, @code{erff}, @code{erfl}, +@code{erf}, @code{exp2f}, @code{exp2l}, @code{exp2}, @code{expm1f}, +@code{expm1l}, @code{expm1}, @code{fdimf}, @code{fdiml}, @code{fdim}, +@code{fmaf}, @code{fmal}, @code{fmaxf}, @code{fmaxl}, @code{fmax}, +@code{fma}, @code{fminf}, @code{fminl}, @code{fmin}, @code{hypotf}, +@code{hypotl}, @code{hypot}, @code{ilogbf}, @code{ilogbl}, @code{ilogb}, +@code{imaxabs}, @code{isblank}, @code{iswblank}, @code{lgammaf}, +@code{lgammal}, @code{lgamma}, @code{llabs}, @code{llrintf}, @code{llrintl}, +@code{llrint}, @code{llroundf}, @code{llroundl}, @code{llround}, +@code{log1pf}, @code{log1pl}, @code{log1p}, @code{log2f}, @code{log2l}, +@code{log2}, @code{logbf}, @code{logbl}, @code{logb}, @code{lrintf}, +@code{lrintl}, @code{lrint}, @code{lroundf}, @code{lroundl}, +@code{lround}, @code{nearbyintf}, @code{nearbyintl}, @code{nearbyint}, +@code{nextafterf}, @code{nextafterl}, @code{nextafter}, +@code{nexttowardf}, @code{nexttowardl}, @code{nexttoward}, +@code{remainderf}, @code{remainderl}, @code{remainder}, @code{remquof}, +@code{remquol}, @code{remquo}, @code{rintf}, @code{rintl}, @code{rint}, +@code{roundf}, @code{roundl}, @code{round}, @code{scalblnf}, +@code{scalblnl}, @code{scalbln}, @code{scalbnf}, @code{scalbnl}, +@code{scalbn}, @code{snprintf}, @code{tgammaf}, @code{tgammal}, +@code{tgamma}, @code{truncf}, @code{truncl}, @code{trunc}, +@code{vfscanf}, @code{vscanf}, @code{vsnprintf} and @code{vsscanf} +are handled as built-in functions +except in strict ISO C90 mode (@option{-ansi} or @option{-std=c90}). + +There are also built-in versions of the ISO C99 functions +@code{acosf}, @code{acosl}, @code{asinf}, @code{asinl}, @code{atan2f}, +@code{atan2l}, @code{atanf}, @code{atanl}, @code{ceilf}, @code{ceill}, +@code{cosf}, @code{coshf}, @code{coshl}, @code{cosl}, @code{expf}, +@code{expl}, @code{fabsf}, @code{fabsl}, @code{floorf}, @code{floorl}, +@code{fmodf}, @code{fmodl}, @code{frexpf}, @code{frexpl}, @code{ldexpf}, +@code{ldexpl}, @code{log10f}, @code{log10l}, @code{logf}, @code{logl}, +@code{modfl}, @code{modf}, @code{powf}, @code{powl}, @code{sinf}, +@code{sinhf}, @code{sinhl}, @code{sinl}, @code{sqrtf}, @code{sqrtl}, +@code{tanf}, @code{tanhf}, @code{tanhl} and @code{tanl} +that are recognized in any mode since ISO C90 reserves these names for +the purpose to which ISO C99 puts them. All these functions have +corresponding versions prefixed with @code{__builtin_}. + +The ISO C94 functions +@code{iswalnum}, @code{iswalpha}, @code{iswcntrl}, @code{iswdigit}, +@code{iswgraph}, @code{iswlower}, @code{iswprint}, @code{iswpunct}, +@code{iswspace}, @code{iswupper}, @code{iswxdigit}, @code{towlower} and +@code{towupper} +are handled as built-in functions +except in strict ISO C90 mode (@option{-ansi} or @option{-std=c90}). + +The ISO C90 functions +@code{abort}, @code{abs}, @code{acos}, @code{asin}, @code{atan2}, +@code{atan}, @code{calloc}, @code{ceil}, @code{cosh}, @code{cos}, +@code{exit}, @code{exp}, @code{fabs}, @code{floor}, @code{fmod}, +@code{fprintf}, @code{fputs}, @code{frexp}, @code{fscanf}, +@code{isalnum}, @code{isalpha}, @code{iscntrl}, @code{isdigit}, +@code{isgraph}, @code{islower}, @code{isprint}, @code{ispunct}, +@code{isspace}, @code{isupper}, @code{isxdigit}, @code{tolower}, +@code{toupper}, @code{labs}, @code{ldexp}, @code{log10}, @code{log}, +@code{malloc}, @code{memchr}, @code{memcmp}, @code{memcpy}, +@code{memset}, @code{modf}, @code{pow}, @code{printf}, @code{putchar}, +@code{puts}, @code{scanf}, @code{sinh}, @code{sin}, @code{snprintf}, +@code{sprintf}, @code{sqrt}, @code{sscanf}, @code{strcat}, +@code{strchr}, @code{strcmp}, @code{strcpy}, @code{strcspn}, +@code{strlen}, @code{strncat}, @code{strncmp}, @code{strncpy}, +@code{strpbrk}, @code{strrchr}, @code{strspn}, @code{strstr}, +@code{tanh}, @code{tan}, @code{vfprintf}, @code{vprintf} and @code{vsprintf} +are all recognized as built-in functions unless +@option{-fno-builtin} is specified (or @option{-fno-builtin-@var{function}} +is specified for an individual function). All of these functions have +corresponding versions prefixed with @code{__builtin_}. + +GCC provides built-in versions of the ISO C99 floating point comparison +macros that avoid raising exceptions for unordered operands. They have +the same names as the standard macros ( @code{isgreater}, +@code{isgreaterequal}, @code{isless}, @code{islessequal}, +@code{islessgreater}, and @code{isunordered}) , with @code{__builtin_} +prefixed. We intend for a library implementor to be able to simply +@code{#define} each standard macro to its built-in equivalent. +In the same fashion, GCC provides @code{fpclassify}, @code{isfinite}, +@code{isinf_sign} and @code{isnormal} built-ins used with +@code{__builtin_} prefixed. The @code{isinf} and @code{isnan} +builtins appear both with and without the @code{__builtin_} prefix. + +@deftypefn {Built-in Function} int __builtin_types_compatible_p (@var{type1}, @var{type2}) + +You can use the built-in function @code{__builtin_types_compatible_p} to +determine whether two types are the same. + +This built-in function returns 1 if the unqualified versions of the +types @var{type1} and @var{type2} (which are types, not expressions) are +compatible, 0 otherwise. The result of this built-in function can be +used in integer constant expressions. + +This built-in function ignores top level qualifiers (e.g., @code{const}, +@code{volatile}). For example, @code{int} is equivalent to @code{const +int}. + +The type @code{int[]} and @code{int[5]} are compatible. On the other +hand, @code{int} and @code{char *} are not compatible, even if the size +of their types, on the particular architecture are the same. Also, the +amount of pointer indirection is taken into account when determining +similarity. Consequently, @code{short *} is not similar to +@code{short **}. Furthermore, two types that are typedefed are +considered compatible if their underlying types are compatible. + +An @code{enum} type is not considered to be compatible with another +@code{enum} type even if both are compatible with the same integer +type; this is what the C standard specifies. +For example, @code{enum @{foo, bar@}} is not similar to +@code{enum @{hot, dog@}}. + +You would typically use this function in code whose execution varies +depending on the arguments' types. For example: + +@smallexample +#define foo(x) \ + (@{ \ + typeof (x) tmp = (x); \ + if (__builtin_types_compatible_p (typeof (x), long double)) \ + tmp = foo_long_double (tmp); \ + else if (__builtin_types_compatible_p (typeof (x), double)) \ + tmp = foo_double (tmp); \ + else if (__builtin_types_compatible_p (typeof (x), float)) \ + tmp = foo_float (tmp); \ + else \ + abort (); \ + tmp; \ + @}) +@end smallexample + +@emph{Note:} This construct is only available for C@. + +@end deftypefn + +@deftypefn {Built-in Function} @var{type} __builtin_choose_expr (@var{const_exp}, @var{exp1}, @var{exp2}) + +You can use the built-in function @code{__builtin_choose_expr} to +evaluate code depending on the value of a constant expression. This +built-in function returns @var{exp1} if @var{const_exp}, which is an +integer constant expression, is nonzero. Otherwise it returns @var{exp2}. + +This built-in function is analogous to the @samp{? :} operator in C, +except that the expression returned has its type unaltered by promotion +rules. Also, the built-in function does not evaluate the expression +that was not chosen. For example, if @var{const_exp} evaluates to true, +@var{exp2} is not evaluated even if it has side-effects. + +This built-in function can return an lvalue if the chosen argument is an +lvalue. + +If @var{exp1} is returned, the return type is the same as @var{exp1}'s +type. Similarly, if @var{exp2} is returned, its return type is the same +as @var{exp2}. + +Example: + +@smallexample +#define foo(x) \ + __builtin_choose_expr ( \ + __builtin_types_compatible_p (typeof (x), double), \ + foo_double (x), \ + __builtin_choose_expr ( \ + __builtin_types_compatible_p (typeof (x), float), \ + foo_float (x), \ + /* @r{The void expression results in a compile-time error} \ + @r{when assigning the result to something.} */ \ + (void)0)) +@end smallexample + +@emph{Note:} This construct is only available for C@. Furthermore, the +unused expression (@var{exp1} or @var{exp2} depending on the value of +@var{const_exp}) may still generate syntax errors. This may change in +future revisions. + +@end deftypefn + +@deftypefn {Built-in Function} int __builtin_constant_p (@var{exp}) +You can use the built-in function @code{__builtin_constant_p} to +determine if a value is known to be constant at compile-time and hence +that GCC can perform constant-folding on expressions involving that +value. The argument of the function is the value to test. The function +returns the integer 1 if the argument is known to be a compile-time +constant and 0 if it is not known to be a compile-time constant. A +return of 0 does not indicate that the value is @emph{not} a constant, +but merely that GCC cannot prove it is a constant with the specified +value of the @option{-O} option. + +You would typically use this function in an embedded application where +memory was a critical resource. If you have some complex calculation, +you may want it to be folded if it involves constants, but need to call +a function if it does not. For example: + +@smallexample +#define Scale_Value(X) \ + (__builtin_constant_p (X) \ + ? ((X) * SCALE + OFFSET) : Scale (X)) +@end smallexample + +You may use this built-in function in either a macro or an inline +function. However, if you use it in an inlined function and pass an +argument of the function as the argument to the built-in, GCC will +never return 1 when you call the inline function with a string constant +or compound literal (@pxref{Compound Literals}) and will not return 1 +when you pass a constant numeric value to the inline function unless you +specify the @option{-O} option. + +You may also use @code{__builtin_constant_p} in initializers for static +data. For instance, you can write + +@smallexample +static const int table[] = @{ + __builtin_constant_p (EXPRESSION) ? (EXPRESSION) : -1, + /* @r{@dots{}} */ +@}; +@end smallexample + +@noindent +This is an acceptable initializer even if @var{EXPRESSION} is not a +constant expression, including the case where +@code{__builtin_constant_p} returns 1 because @var{EXPRESSION} can be +folded to a constant but @var{EXPRESSION} contains operands that would +not otherwise be permitted in a static initializer (for example, +@code{0 && foo ()}). GCC must be more conservative about evaluating the +built-in in this case, because it has no opportunity to perform +optimization. + +Previous versions of GCC did not accept this built-in in data +initializers. The earliest version where it is completely safe is +3.0.1. +@end deftypefn + +@deftypefn {Built-in Function} long __builtin_expect (long @var{exp}, long @var{c}) +@opindex fprofile-arcs +You may use @code{__builtin_expect} to provide the compiler with +branch prediction information. In general, you should prefer to +use actual profile feedback for this (@option{-fprofile-arcs}), as +programmers are notoriously bad at predicting how their programs +actually perform. However, there are applications in which this +data is hard to collect. + +The return value is the value of @var{exp}, which should be an integral +expression. The semantics of the built-in are that it is expected that +@var{exp} == @var{c}. For example: + +@smallexample +if (__builtin_expect (x, 0)) + foo (); +@end smallexample + +@noindent +would indicate that we do not expect to call @code{foo}, since +we expect @code{x} to be zero. Since you are limited to integral +expressions for @var{exp}, you should use constructions such as + +@smallexample +if (__builtin_expect (ptr != NULL, 1)) + error (); +@end smallexample + +@noindent +when testing pointer or floating-point values. +@end deftypefn + +@deftypefn {Built-in Function} void __builtin_trap (void) +This function causes the program to exit abnormally. GCC implements +this function by using a target-dependent mechanism (such as +intentionally executing an illegal instruction) or by calling +@code{abort}. The mechanism used may vary from release to release so +you should not rely on any particular implementation. +@end deftypefn + +@deftypefn {Built-in Function} void __builtin_unreachable (void) +If control flow reaches the point of the @code{__builtin_unreachable}, +the program is undefined. It is useful in situations where the +compiler cannot deduce the unreachability of the code. + +One such case is immediately following an @code{asm} statement that +will either never terminate, or one that transfers control elsewhere +and never returns. In this example, without the +@code{__builtin_unreachable}, GCC would issue a warning that control +reaches the end of a non-void function. It would also generate code +to return after the @code{asm}. + +@smallexample +int f (int c, int v) +@{ + if (c) + @{ + return v; + @} + else + @{ + asm("jmp error_handler"); + __builtin_unreachable (); + @} +@} +@end smallexample + +Because the @code{asm} statement unconditionally transfers control out +of the function, control will never reach the end of the function +body. The @code{__builtin_unreachable} is in fact unreachable and +communicates this fact to the compiler. + +Another use for @code{__builtin_unreachable} is following a call a +function that never returns but that is not declared +@code{__attribute__((noreturn))}, as in this example: + +@smallexample +void function_that_never_returns (void); + +int g (int c) +@{ + if (c) + @{ + return 1; + @} + else + @{ + function_that_never_returns (); + __builtin_unreachable (); + @} +@} +@end smallexample + +@end deftypefn + +@deftypefn {Built-in Function} void __builtin___clear_cache (char *@var{begin}, char *@var{end}) +This function is used to flush the processor's instruction cache for +the region of memory between @var{begin} inclusive and @var{end} +exclusive. Some targets require that the instruction cache be +flushed, after modifying memory containing code, in order to obtain +deterministic behavior. + +If the target does not require instruction cache flushes, +@code{__builtin___clear_cache} has no effect. Otherwise either +instructions are emitted in-line to clear the instruction cache or a +call to the @code{__clear_cache} function in libgcc is made. +@end deftypefn + +@deftypefn {Built-in Function} void __builtin_prefetch (const void *@var{addr}, ...) +This function is used to minimize cache-miss latency by moving data into +a cache before it is accessed. +You can insert calls to @code{__builtin_prefetch} into code for which +you know addresses of data in memory that is likely to be accessed soon. +If the target supports them, data prefetch instructions will be generated. +If the prefetch is done early enough before the access then the data will +be in the cache by the time it is accessed. + +The value of @var{addr} is the address of the memory to prefetch. +There are two optional arguments, @var{rw} and @var{locality}. +The value of @var{rw} is a compile-time constant one or zero; one +means that the prefetch is preparing for a write to the memory address +and zero, the default, means that the prefetch is preparing for a read. +The value @var{locality} must be a compile-time constant integer between +zero and three. A value of zero means that the data has no temporal +locality, so it need not be left in the cache after the access. A value +of three means that the data has a high degree of temporal locality and +should be left in all levels of cache possible. Values of one and two +mean, respectively, a low or moderate degree of temporal locality. The +default is three. + +@smallexample +for (i = 0; i < n; i++) + @{ + a[i] = a[i] + b[i]; + __builtin_prefetch (&a[i+j], 1, 1); + __builtin_prefetch (&b[i+j], 0, 1); + /* @r{@dots{}} */ + @} +@end smallexample + +Data prefetch does not generate faults if @var{addr} is invalid, but +the address expression itself must be valid. For example, a prefetch +of @code{p->next} will not fault if @code{p->next} is not a valid +address, but evaluation will fault if @code{p} is not a valid address. + +If the target does not support data prefetch, the address expression +is evaluated if it includes side effects but no other code is generated +and GCC does not issue a warning. +@end deftypefn + +@deftypefn {Built-in Function} double __builtin_huge_val (void) +Returns a positive infinity, if supported by the floating-point format, +else @code{DBL_MAX}. This function is suitable for implementing the +ISO C macro @code{HUGE_VAL}. +@end deftypefn + +@deftypefn {Built-in Function} float __builtin_huge_valf (void) +Similar to @code{__builtin_huge_val}, except the return type is @code{float}. +@end deftypefn + +@deftypefn {Built-in Function} {long double} __builtin_huge_vall (void) +Similar to @code{__builtin_huge_val}, except the return +type is @code{long double}. +@end deftypefn + +@deftypefn {Built-in Function} int __builtin_fpclassify (int, int, int, int, int, ...) +This built-in implements the C99 fpclassify functionality. The first +five int arguments should be the target library's notion of the +possible FP classes and are used for return values. They must be +constant values and they must appear in this order: @code{FP_NAN}, +@code{FP_INFINITE}, @code{FP_NORMAL}, @code{FP_SUBNORMAL} and +@code{FP_ZERO}. The ellipsis is for exactly one floating point value +to classify. GCC treats the last argument as type-generic, which +means it does not do default promotion from float to double. +@end deftypefn + +@deftypefn {Built-in Function} double __builtin_inf (void) +Similar to @code{__builtin_huge_val}, except a warning is generated +if the target floating-point format does not support infinities. +@end deftypefn + +@deftypefn {Built-in Function} _Decimal32 __builtin_infd32 (void) +Similar to @code{__builtin_inf}, except the return type is @code{_Decimal32}. +@end deftypefn + +@deftypefn {Built-in Function} _Decimal64 __builtin_infd64 (void) +Similar to @code{__builtin_inf}, except the return type is @code{_Decimal64}. +@end deftypefn + +@deftypefn {Built-in Function} _Decimal128 __builtin_infd128 (void) +Similar to @code{__builtin_inf}, except the return type is @code{_Decimal128}. +@end deftypefn + +@deftypefn {Built-in Function} float __builtin_inff (void) +Similar to @code{__builtin_inf}, except the return type is @code{float}. +This function is suitable for implementing the ISO C99 macro @code{INFINITY}. +@end deftypefn + +@deftypefn {Built-in Function} {long double} __builtin_infl (void) +Similar to @code{__builtin_inf}, except the return +type is @code{long double}. +@end deftypefn + +@deftypefn {Built-in Function} int __builtin_isinf_sign (...) +Similar to @code{isinf}, except the return value will be negative for +an argument of @code{-Inf}. Note while the parameter list is an +ellipsis, this function only accepts exactly one floating point +argument. GCC treats this parameter as type-generic, which means it +does not do default promotion from float to double. +@end deftypefn + +@deftypefn {Built-in Function} double __builtin_nan (const char *str) +This is an implementation of the ISO C99 function @code{nan}. + +Since ISO C99 defines this function in terms of @code{strtod}, which we +do not implement, a description of the parsing is in order. The string +is parsed as by @code{strtol}; that is, the base is recognized by +leading @samp{0} or @samp{0x} prefixes. The number parsed is placed +in the significand such that the least significant bit of the number +is at the least significant bit of the significand. The number is +truncated to fit the significand field provided. The significand is +forced to be a quiet NaN@. + +This function, if given a string literal all of which would have been +consumed by strtol, is evaluated early enough that it is considered a +compile-time constant. +@end deftypefn + +@deftypefn {Built-in Function} _Decimal32 __builtin_nand32 (const char *str) +Similar to @code{__builtin_nan}, except the return type is @code{_Decimal32}. +@end deftypefn + +@deftypefn {Built-in Function} _Decimal64 __builtin_nand64 (const char *str) +Similar to @code{__builtin_nan}, except the return type is @code{_Decimal64}. +@end deftypefn + +@deftypefn {Built-in Function} _Decimal128 __builtin_nand128 (const char *str) +Similar to @code{__builtin_nan}, except the return type is @code{_Decimal128}. +@end deftypefn + +@deftypefn {Built-in Function} float __builtin_nanf (const char *str) +Similar to @code{__builtin_nan}, except the return type is @code{float}. +@end deftypefn + +@deftypefn {Built-in Function} {long double} __builtin_nanl (const char *str) +Similar to @code{__builtin_nan}, except the return type is @code{long double}. +@end deftypefn + +@deftypefn {Built-in Function} double __builtin_nans (const char *str) +Similar to @code{__builtin_nan}, except the significand is forced +to be a signaling NaN@. The @code{nans} function is proposed by +@uref{http://www.open-std.org/jtc1/sc22/wg14/www/docs/n965.htm,,WG14 N965}. +@end deftypefn + +@deftypefn {Built-in Function} float __builtin_nansf (const char *str) +Similar to @code{__builtin_nans}, except the return type is @code{float}. +@end deftypefn + +@deftypefn {Built-in Function} {long double} __builtin_nansl (const char *str) +Similar to @code{__builtin_nans}, except the return type is @code{long double}. +@end deftypefn + +@deftypefn {Built-in Function} int __builtin_ffs (unsigned int x) +Returns one plus the index of the least significant 1-bit of @var{x}, or +if @var{x} is zero, returns zero. +@end deftypefn + +@deftypefn {Built-in Function} int __builtin_clz (unsigned int x) +Returns the number of leading 0-bits in @var{x}, starting at the most +significant bit position. If @var{x} is 0, the result is undefined. +@end deftypefn + +@deftypefn {Built-in Function} int __builtin_ctz (unsigned int x) +Returns the number of trailing 0-bits in @var{x}, starting at the least +significant bit position. If @var{x} is 0, the result is undefined. +@end deftypefn + +@deftypefn {Built-in Function} int __builtin_popcount (unsigned int x) +Returns the number of 1-bits in @var{x}. +@end deftypefn + +@deftypefn {Built-in Function} int __builtin_parity (unsigned int x) +Returns the parity of @var{x}, i.e.@: the number of 1-bits in @var{x} +modulo 2. +@end deftypefn + +@deftypefn {Built-in Function} int __builtin_ffsl (unsigned long) +Similar to @code{__builtin_ffs}, except the argument type is +@code{unsigned long}. +@end deftypefn + +@deftypefn {Built-in Function} int __builtin_clzl (unsigned long) +Similar to @code{__builtin_clz}, except the argument type is +@code{unsigned long}. +@end deftypefn + +@deftypefn {Built-in Function} int __builtin_ctzl (unsigned long) +Similar to @code{__builtin_ctz}, except the argument type is +@code{unsigned long}. +@end deftypefn + +@deftypefn {Built-in Function} int __builtin_popcountl (unsigned long) +Similar to @code{__builtin_popcount}, except the argument type is +@code{unsigned long}. +@end deftypefn + +@deftypefn {Built-in Function} int __builtin_parityl (unsigned long) +Similar to @code{__builtin_parity}, except the argument type is +@code{unsigned long}. +@end deftypefn + +@deftypefn {Built-in Function} int __builtin_ffsll (unsigned long long) +Similar to @code{__builtin_ffs}, except the argument type is +@code{unsigned long long}. +@end deftypefn + +@deftypefn {Built-in Function} int __builtin_clzll (unsigned long long) +Similar to @code{__builtin_clz}, except the argument type is +@code{unsigned long long}. +@end deftypefn + +@deftypefn {Built-in Function} int __builtin_ctzll (unsigned long long) +Similar to @code{__builtin_ctz}, except the argument type is +@code{unsigned long long}. +@end deftypefn + +@deftypefn {Built-in Function} int __builtin_popcountll (unsigned long long) +Similar to @code{__builtin_popcount}, except the argument type is +@code{unsigned long long}. +@end deftypefn + +@deftypefn {Built-in Function} int __builtin_parityll (unsigned long long) +Similar to @code{__builtin_parity}, except the argument type is +@code{unsigned long long}. +@end deftypefn + +@deftypefn {Built-in Function} double __builtin_powi (double, int) +Returns the first argument raised to the power of the second. Unlike the +@code{pow} function no guarantees about precision and rounding are made. +@end deftypefn + +@deftypefn {Built-in Function} float __builtin_powif (float, int) +Similar to @code{__builtin_powi}, except the argument and return types +are @code{float}. +@end deftypefn + +@deftypefn {Built-in Function} {long double} __builtin_powil (long double, int) +Similar to @code{__builtin_powi}, except the argument and return types +are @code{long double}. +@end deftypefn + +@deftypefn {Built-in Function} int32_t __builtin_bswap32 (int32_t x) +Returns @var{x} with the order of the bytes reversed; for example, +@code{0xaabbccdd} becomes @code{0xddccbbaa}. Byte here always means +exactly 8 bits. +@end deftypefn + +@deftypefn {Built-in Function} int64_t __builtin_bswap64 (int64_t x) +Similar to @code{__builtin_bswap32}, except the argument and return types +are 64-bit. +@end deftypefn + +@node Target Builtins +@section Built-in Functions Specific to Particular Target Machines + +On some target machines, GCC supports many built-in functions specific +to those machines. Generally these generate calls to specific machine +instructions, but allow the compiler to schedule those calls. + +@menu +* Alpha Built-in Functions:: +* ARM iWMMXt Built-in Functions:: +* ARM NEON Intrinsics:: +* Blackfin Built-in Functions:: +* FR-V Built-in Functions:: +* X86 Built-in Functions:: +* MIPS DSP Built-in Functions:: +* MIPS Paired-Single Support:: +* MIPS Loongson Built-in Functions:: +* Other MIPS Built-in Functions:: +* picoChip Built-in Functions:: +* PowerPC AltiVec/VSX Built-in Functions:: +* RX Built-in Functions:: +* SPARC VIS Built-in Functions:: +* SPU Built-in Functions:: +@end menu + +@node Alpha Built-in Functions +@subsection Alpha Built-in Functions + +These built-in functions are available for the Alpha family of +processors, depending on the command-line switches used. + +The following built-in functions are always available. They +all generate the machine instruction that is part of the name. + +@smallexample +long __builtin_alpha_implver (void) +long __builtin_alpha_rpcc (void) +long __builtin_alpha_amask (long) +long __builtin_alpha_cmpbge (long, long) +long __builtin_alpha_extbl (long, long) +long __builtin_alpha_extwl (long, long) +long __builtin_alpha_extll (long, long) +long __builtin_alpha_extql (long, long) +long __builtin_alpha_extwh (long, long) +long __builtin_alpha_extlh (long, long) +long __builtin_alpha_extqh (long, long) +long __builtin_alpha_insbl (long, long) +long __builtin_alpha_inswl (long, long) +long __builtin_alpha_insll (long, long) +long __builtin_alpha_insql (long, long) +long __builtin_alpha_inswh (long, long) +long __builtin_alpha_inslh (long, long) +long __builtin_alpha_insqh (long, long) +long __builtin_alpha_mskbl (long, long) +long __builtin_alpha_mskwl (long, long) +long __builtin_alpha_mskll (long, long) +long __builtin_alpha_mskql (long, long) +long __builtin_alpha_mskwh (long, long) +long __builtin_alpha_msklh (long, long) +long __builtin_alpha_mskqh (long, long) +long __builtin_alpha_umulh (long, long) +long __builtin_alpha_zap (long, long) +long __builtin_alpha_zapnot (long, long) +@end smallexample + +The following built-in functions are always with @option{-mmax} +or @option{-mcpu=@var{cpu}} where @var{cpu} is @code{pca56} or +later. They all generate the machine instruction that is part +of the name. + +@smallexample +long __builtin_alpha_pklb (long) +long __builtin_alpha_pkwb (long) +long __builtin_alpha_unpkbl (long) +long __builtin_alpha_unpkbw (long) +long __builtin_alpha_minub8 (long, long) +long __builtin_alpha_minsb8 (long, long) +long __builtin_alpha_minuw4 (long, long) +long __builtin_alpha_minsw4 (long, long) +long __builtin_alpha_maxub8 (long, long) +long __builtin_alpha_maxsb8 (long, long) +long __builtin_alpha_maxuw4 (long, long) +long __builtin_alpha_maxsw4 (long, long) +long __builtin_alpha_perr (long, long) +@end smallexample + +The following built-in functions are always with @option{-mcix} +or @option{-mcpu=@var{cpu}} where @var{cpu} is @code{ev67} or +later. They all generate the machine instruction that is part +of the name. + +@smallexample +long __builtin_alpha_cttz (long) +long __builtin_alpha_ctlz (long) +long __builtin_alpha_ctpop (long) +@end smallexample + +The following builtins are available on systems that use the OSF/1 +PALcode. Normally they invoke the @code{rduniq} and @code{wruniq} +PAL calls, but when invoked with @option{-mtls-kernel}, they invoke +@code{rdval} and @code{wrval}. + +@smallexample +void *__builtin_thread_pointer (void) +void __builtin_set_thread_pointer (void *) +@end smallexample + +@node ARM iWMMXt Built-in Functions +@subsection ARM iWMMXt Built-in Functions + +These built-in functions are available for the ARM family of +processors when the @option{-mcpu=iwmmxt} switch is used: + +@smallexample +typedef int v2si __attribute__ ((vector_size (8))); +typedef short v4hi __attribute__ ((vector_size (8))); +typedef char v8qi __attribute__ ((vector_size (8))); + +int __builtin_arm_getwcx (int) +void __builtin_arm_setwcx (int, int) +int __builtin_arm_textrmsb (v8qi, int) +int __builtin_arm_textrmsh (v4hi, int) +int __builtin_arm_textrmsw (v2si, int) +int __builtin_arm_textrmub (v8qi, int) +int __builtin_arm_textrmuh (v4hi, int) +int __builtin_arm_textrmuw (v2si, int) +v8qi __builtin_arm_tinsrb (v8qi, int) +v4hi __builtin_arm_tinsrh (v4hi, int) +v2si __builtin_arm_tinsrw (v2si, int) +long long __builtin_arm_tmia (long long, int, int) +long long __builtin_arm_tmiabb (long long, int, int) +long long __builtin_arm_tmiabt (long long, int, int) +long long __builtin_arm_tmiaph (long long, int, int) +long long __builtin_arm_tmiatb (long long, int, int) +long long __builtin_arm_tmiatt (long long, int, int) +int __builtin_arm_tmovmskb (v8qi) +int __builtin_arm_tmovmskh (v4hi) +int __builtin_arm_tmovmskw (v2si) +long long __builtin_arm_waccb (v8qi) +long long __builtin_arm_wacch (v4hi) +long long __builtin_arm_waccw (v2si) +v8qi __builtin_arm_waddb (v8qi, v8qi) +v8qi __builtin_arm_waddbss (v8qi, v8qi) +v8qi __builtin_arm_waddbus (v8qi, v8qi) +v4hi __builtin_arm_waddh (v4hi, v4hi) +v4hi __builtin_arm_waddhss (v4hi, v4hi) +v4hi __builtin_arm_waddhus (v4hi, v4hi) +v2si __builtin_arm_waddw (v2si, v2si) +v2si __builtin_arm_waddwss (v2si, v2si) +v2si __builtin_arm_waddwus (v2si, v2si) +v8qi __builtin_arm_walign (v8qi, v8qi, int) +long long __builtin_arm_wand(long long, long long) +long long __builtin_arm_wandn (long long, long long) +v8qi __builtin_arm_wavg2b (v8qi, v8qi) +v8qi __builtin_arm_wavg2br (v8qi, v8qi) +v4hi __builtin_arm_wavg2h (v4hi, v4hi) +v4hi __builtin_arm_wavg2hr (v4hi, v4hi) +v8qi __builtin_arm_wcmpeqb (v8qi, v8qi) +v4hi __builtin_arm_wcmpeqh (v4hi, v4hi) +v2si __builtin_arm_wcmpeqw (v2si, v2si) +v8qi __builtin_arm_wcmpgtsb (v8qi, v8qi) +v4hi __builtin_arm_wcmpgtsh (v4hi, v4hi) +v2si __builtin_arm_wcmpgtsw (v2si, v2si) +v8qi __builtin_arm_wcmpgtub (v8qi, v8qi) +v4hi __builtin_arm_wcmpgtuh (v4hi, v4hi) +v2si __builtin_arm_wcmpgtuw (v2si, v2si) +long long __builtin_arm_wmacs (long long, v4hi, v4hi) +long long __builtin_arm_wmacsz (v4hi, v4hi) +long long __builtin_arm_wmacu (long long, v4hi, v4hi) +long long __builtin_arm_wmacuz (v4hi, v4hi) +v4hi __builtin_arm_wmadds (v4hi, v4hi) +v4hi __builtin_arm_wmaddu (v4hi, v4hi) +v8qi __builtin_arm_wmaxsb (v8qi, v8qi) +v4hi __builtin_arm_wmaxsh (v4hi, v4hi) +v2si __builtin_arm_wmaxsw (v2si, v2si) +v8qi __builtin_arm_wmaxub (v8qi, v8qi) +v4hi __builtin_arm_wmaxuh (v4hi, v4hi) +v2si __builtin_arm_wmaxuw (v2si, v2si) +v8qi __builtin_arm_wminsb (v8qi, v8qi) +v4hi __builtin_arm_wminsh (v4hi, v4hi) +v2si __builtin_arm_wminsw (v2si, v2si) +v8qi __builtin_arm_wminub (v8qi, v8qi) +v4hi __builtin_arm_wminuh (v4hi, v4hi) +v2si __builtin_arm_wminuw (v2si, v2si) +v4hi __builtin_arm_wmulsm (v4hi, v4hi) +v4hi __builtin_arm_wmulul (v4hi, v4hi) +v4hi __builtin_arm_wmulum (v4hi, v4hi) +long long __builtin_arm_wor (long long, long long) +v2si __builtin_arm_wpackdss (long long, long long) +v2si __builtin_arm_wpackdus (long long, long long) +v8qi __builtin_arm_wpackhss (v4hi, v4hi) +v8qi __builtin_arm_wpackhus (v4hi, v4hi) +v4hi __builtin_arm_wpackwss (v2si, v2si) +v4hi __builtin_arm_wpackwus (v2si, v2si) +long long __builtin_arm_wrord (long long, long long) +long long __builtin_arm_wrordi (long long, int) +v4hi __builtin_arm_wrorh (v4hi, long long) +v4hi __builtin_arm_wrorhi (v4hi, int) +v2si __builtin_arm_wrorw (v2si, long long) +v2si __builtin_arm_wrorwi (v2si, int) +v2si __builtin_arm_wsadb (v8qi, v8qi) +v2si __builtin_arm_wsadbz (v8qi, v8qi) +v2si __builtin_arm_wsadh (v4hi, v4hi) +v2si __builtin_arm_wsadhz (v4hi, v4hi) +v4hi __builtin_arm_wshufh (v4hi, int) +long long __builtin_arm_wslld (long long, long long) +long long __builtin_arm_wslldi (long long, int) +v4hi __builtin_arm_wsllh (v4hi, long long) +v4hi __builtin_arm_wsllhi (v4hi, int) +v2si __builtin_arm_wsllw (v2si, long long) +v2si __builtin_arm_wsllwi (v2si, int) +long long __builtin_arm_wsrad (long long, long long) +long long __builtin_arm_wsradi (long long, int) +v4hi __builtin_arm_wsrah (v4hi, long long) +v4hi __builtin_arm_wsrahi (v4hi, int) +v2si __builtin_arm_wsraw (v2si, long long) +v2si __builtin_arm_wsrawi (v2si, int) +long long __builtin_arm_wsrld (long long, long long) +long long __builtin_arm_wsrldi (long long, int) +v4hi __builtin_arm_wsrlh (v4hi, long long) +v4hi __builtin_arm_wsrlhi (v4hi, int) +v2si __builtin_arm_wsrlw (v2si, long long) +v2si __builtin_arm_wsrlwi (v2si, int) +v8qi __builtin_arm_wsubb (v8qi, v8qi) +v8qi __builtin_arm_wsubbss (v8qi, v8qi) +v8qi __builtin_arm_wsubbus (v8qi, v8qi) +v4hi __builtin_arm_wsubh (v4hi, v4hi) +v4hi __builtin_arm_wsubhss (v4hi, v4hi) +v4hi __builtin_arm_wsubhus (v4hi, v4hi) +v2si __builtin_arm_wsubw (v2si, v2si) +v2si __builtin_arm_wsubwss (v2si, v2si) +v2si __builtin_arm_wsubwus (v2si, v2si) +v4hi __builtin_arm_wunpckehsb (v8qi) +v2si __builtin_arm_wunpckehsh (v4hi) +long long __builtin_arm_wunpckehsw (v2si) +v4hi __builtin_arm_wunpckehub (v8qi) +v2si __builtin_arm_wunpckehuh (v4hi) +long long __builtin_arm_wunpckehuw (v2si) +v4hi __builtin_arm_wunpckelsb (v8qi) +v2si __builtin_arm_wunpckelsh (v4hi) +long long __builtin_arm_wunpckelsw (v2si) +v4hi __builtin_arm_wunpckelub (v8qi) +v2si __builtin_arm_wunpckeluh (v4hi) +long long __builtin_arm_wunpckeluw (v2si) +v8qi __builtin_arm_wunpckihb (v8qi, v8qi) +v4hi __builtin_arm_wunpckihh (v4hi, v4hi) +v2si __builtin_arm_wunpckihw (v2si, v2si) +v8qi __builtin_arm_wunpckilb (v8qi, v8qi) +v4hi __builtin_arm_wunpckilh (v4hi, v4hi) +v2si __builtin_arm_wunpckilw (v2si, v2si) +long long __builtin_arm_wxor (long long, long long) +long long __builtin_arm_wzero () +@end smallexample + +@node ARM NEON Intrinsics +@subsection ARM NEON Intrinsics + +These built-in intrinsics for the ARM Advanced SIMD extension are available +when the @option{-mfpu=neon} switch is used: + +@include arm-neon-intrinsics.texi + +@node Blackfin Built-in Functions +@subsection Blackfin Built-in Functions + +Currently, there are two Blackfin-specific built-in functions. These are +used for generating @code{CSYNC} and @code{SSYNC} machine insns without +using inline assembly; by using these built-in functions the compiler can +automatically add workarounds for hardware errata involving these +instructions. These functions are named as follows: + +@smallexample +void __builtin_bfin_csync (void) +void __builtin_bfin_ssync (void) +@end smallexample + +@node FR-V Built-in Functions +@subsection FR-V Built-in Functions + +GCC provides many FR-V-specific built-in functions. In general, +these functions are intended to be compatible with those described +by @cite{FR-V Family, Softune C/C++ Compiler Manual (V6), Fujitsu +Semiconductor}. The two exceptions are @code{__MDUNPACKH} and +@code{__MBTOHE}, the gcc forms of which pass 128-bit values by +pointer rather than by value. + +Most of the functions are named after specific FR-V instructions. +Such functions are said to be ``directly mapped'' and are summarized +here in tabular form. + +@menu +* Argument Types:: +* Directly-mapped Integer Functions:: +* Directly-mapped Media Functions:: +* Raw read/write Functions:: +* Other Built-in Functions:: +@end menu + +@node Argument Types +@subsubsection Argument Types + +The arguments to the built-in functions can be divided into three groups: +register numbers, compile-time constants and run-time values. In order +to make this classification clear at a glance, the arguments and return +values are given the following pseudo types: + +@multitable @columnfractions .20 .30 .15 .35 +@item Pseudo type @tab Real C type @tab Constant? @tab Description +@item @code{uh} @tab @code{unsigned short} @tab No @tab an unsigned halfword +@item @code{uw1} @tab @code{unsigned int} @tab No @tab an unsigned word +@item @code{sw1} @tab @code{int} @tab No @tab a signed word +@item @code{uw2} @tab @code{unsigned long long} @tab No +@tab an unsigned doubleword +@item @code{sw2} @tab @code{long long} @tab No @tab a signed doubleword +@item @code{const} @tab @code{int} @tab Yes @tab an integer constant +@item @code{acc} @tab @code{int} @tab Yes @tab an ACC register number +@item @code{iacc} @tab @code{int} @tab Yes @tab an IACC register number +@end multitable + +These pseudo types are not defined by GCC, they are simply a notational +convenience used in this manual. + +Arguments of type @code{uh}, @code{uw1}, @code{sw1}, @code{uw2} +and @code{sw2} are evaluated at run time. They correspond to +register operands in the underlying FR-V instructions. + +@code{const} arguments represent immediate operands in the underlying +FR-V instructions. They must be compile-time constants. + +@code{acc} arguments are evaluated at compile time and specify the number +of an accumulator register. For example, an @code{acc} argument of 2 +will select the ACC2 register. + +@code{iacc} arguments are similar to @code{acc} arguments but specify the +number of an IACC register. See @pxref{Other Built-in Functions} +for more details. + +@node Directly-mapped Integer Functions +@subsubsection Directly-mapped Integer Functions + +The functions listed below map directly to FR-V I-type instructions. + +@multitable @columnfractions .45 .32 .23 +@item Function prototype @tab Example usage @tab Assembly output +@item @code{sw1 __ADDSS (sw1, sw1)} +@tab @code{@var{c} = __ADDSS (@var{a}, @var{b})} +@tab @code{ADDSS @var{a},@var{b},@var{c}} +@item @code{sw1 __SCAN (sw1, sw1)} +@tab @code{@var{c} = __SCAN (@var{a}, @var{b})} +@tab @code{SCAN @var{a},@var{b},@var{c}} +@item @code{sw1 __SCUTSS (sw1)} +@tab @code{@var{b} = __SCUTSS (@var{a})} +@tab @code{SCUTSS @var{a},@var{b}} +@item @code{sw1 __SLASS (sw1, sw1)} +@tab @code{@var{c} = __SLASS (@var{a}, @var{b})} +@tab @code{SLASS @var{a},@var{b},@var{c}} +@item @code{void __SMASS (sw1, sw1)} +@tab @code{__SMASS (@var{a}, @var{b})} +@tab @code{SMASS @var{a},@var{b}} +@item @code{void __SMSSS (sw1, sw1)} +@tab @code{__SMSSS (@var{a}, @var{b})} +@tab @code{SMSSS @var{a},@var{b}} +@item @code{void __SMU (sw1, sw1)} +@tab @code{__SMU (@var{a}, @var{b})} +@tab @code{SMU @var{a},@var{b}} +@item @code{sw2 __SMUL (sw1, sw1)} +@tab @code{@var{c} = __SMUL (@var{a}, @var{b})} +@tab @code{SMUL @var{a},@var{b},@var{c}} +@item @code{sw1 __SUBSS (sw1, sw1)} +@tab @code{@var{c} = __SUBSS (@var{a}, @var{b})} +@tab @code{SUBSS @var{a},@var{b},@var{c}} +@item @code{uw2 __UMUL (uw1, uw1)} +@tab @code{@var{c} = __UMUL (@var{a}, @var{b})} +@tab @code{UMUL @var{a},@var{b},@var{c}} +@end multitable + +@node Directly-mapped Media Functions +@subsubsection Directly-mapped Media Functions + +The functions listed below map directly to FR-V M-type instructions. + +@multitable @columnfractions .45 .32 .23 +@item Function prototype @tab Example usage @tab Assembly output +@item @code{uw1 __MABSHS (sw1)} +@tab @code{@var{b} = __MABSHS (@var{a})} +@tab @code{MABSHS @var{a},@var{b}} +@item @code{void __MADDACCS (acc, acc)} +@tab @code{__MADDACCS (@var{b}, @var{a})} +@tab @code{MADDACCS @var{a},@var{b}} +@item @code{sw1 __MADDHSS (sw1, sw1)} +@tab @code{@var{c} = __MADDHSS (@var{a}, @var{b})} +@tab @code{MADDHSS @var{a},@var{b},@var{c}} +@item @code{uw1 __MADDHUS (uw1, uw1)} +@tab @code{@var{c} = __MADDHUS (@var{a}, @var{b})} +@tab @code{MADDHUS @var{a},@var{b},@var{c}} +@item @code{uw1 __MAND (uw1, uw1)} +@tab @code{@var{c} = __MAND (@var{a}, @var{b})} +@tab @code{MAND @var{a},@var{b},@var{c}} +@item @code{void __MASACCS (acc, acc)} +@tab @code{__MASACCS (@var{b}, @var{a})} +@tab @code{MASACCS @var{a},@var{b}} +@item @code{uw1 __MAVEH (uw1, uw1)} +@tab @code{@var{c} = __MAVEH (@var{a}, @var{b})} +@tab @code{MAVEH @var{a},@var{b},@var{c}} +@item @code{uw2 __MBTOH (uw1)} +@tab @code{@var{b} = __MBTOH (@var{a})} +@tab @code{MBTOH @var{a},@var{b}} +@item @code{void __MBTOHE (uw1 *, uw1)} +@tab @code{__MBTOHE (&@var{b}, @var{a})} +@tab @code{MBTOHE @var{a},@var{b}} +@item @code{void __MCLRACC (acc)} +@tab @code{__MCLRACC (@var{a})} +@tab @code{MCLRACC @var{a}} +@item @code{void __MCLRACCA (void)} +@tab @code{__MCLRACCA ()} +@tab @code{MCLRACCA} +@item @code{uw1 __Mcop1 (uw1, uw1)} +@tab @code{@var{c} = __Mcop1 (@var{a}, @var{b})} +@tab @code{Mcop1 @var{a},@var{b},@var{c}} +@item @code{uw1 __Mcop2 (uw1, uw1)} +@tab @code{@var{c} = __Mcop2 (@var{a}, @var{b})} +@tab @code{Mcop2 @var{a},@var{b},@var{c}} +@item @code{uw1 __MCPLHI (uw2, const)} +@tab @code{@var{c} = __MCPLHI (@var{a}, @var{b})} +@tab @code{MCPLHI @var{a},#@var{b},@var{c}} +@item @code{uw1 __MCPLI (uw2, const)} +@tab @code{@var{c} = __MCPLI (@var{a}, @var{b})} +@tab @code{MCPLI @var{a},#@var{b},@var{c}} +@item @code{void __MCPXIS (acc, sw1, sw1)} +@tab @code{__MCPXIS (@var{c}, @var{a}, @var{b})} +@tab @code{MCPXIS @var{a},@var{b},@var{c}} +@item @code{void __MCPXIU (acc, uw1, uw1)} +@tab @code{__MCPXIU (@var{c}, @var{a}, @var{b})} +@tab @code{MCPXIU @var{a},@var{b},@var{c}} +@item @code{void __MCPXRS (acc, sw1, sw1)} +@tab @code{__MCPXRS (@var{c}, @var{a}, @var{b})} +@tab @code{MCPXRS @var{a},@var{b},@var{c}} +@item @code{void __MCPXRU (acc, uw1, uw1)} +@tab @code{__MCPXRU (@var{c}, @var{a}, @var{b})} +@tab @code{MCPXRU @var{a},@var{b},@var{c}} +@item @code{uw1 __MCUT (acc, uw1)} +@tab @code{@var{c} = __MCUT (@var{a}, @var{b})} +@tab @code{MCUT @var{a},@var{b},@var{c}} +@item @code{uw1 __MCUTSS (acc, sw1)} +@tab @code{@var{c} = __MCUTSS (@var{a}, @var{b})} +@tab @code{MCUTSS @var{a},@var{b},@var{c}} +@item @code{void __MDADDACCS (acc, acc)} +@tab @code{__MDADDACCS (@var{b}, @var{a})} +@tab @code{MDADDACCS @var{a},@var{b}} +@item @code{void __MDASACCS (acc, acc)} +@tab @code{__MDASACCS (@var{b}, @var{a})} +@tab @code{MDASACCS @var{a},@var{b}} +@item @code{uw2 __MDCUTSSI (acc, const)} +@tab @code{@var{c} = __MDCUTSSI (@var{a}, @var{b})} +@tab @code{MDCUTSSI @var{a},#@var{b},@var{c}} +@item @code{uw2 __MDPACKH (uw2, uw2)} +@tab @code{@var{c} = __MDPACKH (@var{a}, @var{b})} +@tab @code{MDPACKH @var{a},@var{b},@var{c}} +@item @code{uw2 __MDROTLI (uw2, const)} +@tab @code{@var{c} = __MDROTLI (@var{a}, @var{b})} +@tab @code{MDROTLI @var{a},#@var{b},@var{c}} +@item @code{void __MDSUBACCS (acc, acc)} +@tab @code{__MDSUBACCS (@var{b}, @var{a})} +@tab @code{MDSUBACCS @var{a},@var{b}} +@item @code{void __MDUNPACKH (uw1 *, uw2)} +@tab @code{__MDUNPACKH (&@var{b}, @var{a})} +@tab @code{MDUNPACKH @var{a},@var{b}} +@item @code{uw2 __MEXPDHD (uw1, const)} +@tab @code{@var{c} = __MEXPDHD (@var{a}, @var{b})} +@tab @code{MEXPDHD @var{a},#@var{b},@var{c}} +@item @code{uw1 __MEXPDHW (uw1, const)} +@tab @code{@var{c} = __MEXPDHW (@var{a}, @var{b})} +@tab @code{MEXPDHW @var{a},#@var{b},@var{c}} +@item @code{uw1 __MHDSETH (uw1, const)} +@tab @code{@var{c} = __MHDSETH (@var{a}, @var{b})} +@tab @code{MHDSETH @var{a},#@var{b},@var{c}} +@item @code{sw1 __MHDSETS (const)} +@tab @code{@var{b} = __MHDSETS (@var{a})} +@tab @code{MHDSETS #@var{a},@var{b}} +@item @code{uw1 __MHSETHIH (uw1, const)} +@tab @code{@var{b} = __MHSETHIH (@var{b}, @var{a})} +@tab @code{MHSETHIH #@var{a},@var{b}} +@item @code{sw1 __MHSETHIS (sw1, const)} +@tab @code{@var{b} = __MHSETHIS (@var{b}, @var{a})} +@tab @code{MHSETHIS #@var{a},@var{b}} +@item @code{uw1 __MHSETLOH (uw1, const)} +@tab @code{@var{b} = __MHSETLOH (@var{b}, @var{a})} +@tab @code{MHSETLOH #@var{a},@var{b}} +@item @code{sw1 __MHSETLOS (sw1, const)} +@tab @code{@var{b} = __MHSETLOS (@var{b}, @var{a})} +@tab @code{MHSETLOS #@var{a},@var{b}} +@item @code{uw1 __MHTOB (uw2)} +@tab @code{@var{b} = __MHTOB (@var{a})} +@tab @code{MHTOB @var{a},@var{b}} +@item @code{void __MMACHS (acc, sw1, sw1)} +@tab @code{__MMACHS (@var{c}, @var{a}, @var{b})} +@tab @code{MMACHS @var{a},@var{b},@var{c}} +@item @code{void __MMACHU (acc, uw1, uw1)} +@tab @code{__MMACHU (@var{c}, @var{a}, @var{b})} +@tab @code{MMACHU @var{a},@var{b},@var{c}} +@item @code{void __MMRDHS (acc, sw1, sw1)} +@tab @code{__MMRDHS (@var{c}, @var{a}, @var{b})} +@tab @code{MMRDHS @var{a},@var{b},@var{c}} +@item @code{void __MMRDHU (acc, uw1, uw1)} +@tab @code{__MMRDHU (@var{c}, @var{a}, @var{b})} +@tab @code{MMRDHU @var{a},@var{b},@var{c}} +@item @code{void __MMULHS (acc, sw1, sw1)} +@tab @code{__MMULHS (@var{c}, @var{a}, @var{b})} +@tab @code{MMULHS @var{a},@var{b},@var{c}} +@item @code{void __MMULHU (acc, uw1, uw1)} +@tab @code{__MMULHU (@var{c}, @var{a}, @var{b})} +@tab @code{MMULHU @var{a},@var{b},@var{c}} +@item @code{void __MMULXHS (acc, sw1, sw1)} +@tab @code{__MMULXHS (@var{c}, @var{a}, @var{b})} +@tab @code{MMULXHS @var{a},@var{b},@var{c}} +@item @code{void __MMULXHU (acc, uw1, uw1)} +@tab @code{__MMULXHU (@var{c}, @var{a}, @var{b})} +@tab @code{MMULXHU @var{a},@var{b},@var{c}} +@item @code{uw1 __MNOT (uw1)} +@tab @code{@var{b} = __MNOT (@var{a})} +@tab @code{MNOT @var{a},@var{b}} +@item @code{uw1 __MOR (uw1, uw1)} +@tab @code{@var{c} = __MOR (@var{a}, @var{b})} +@tab @code{MOR @var{a},@var{b},@var{c}} +@item @code{uw1 __MPACKH (uh, uh)} +@tab @code{@var{c} = __MPACKH (@var{a}, @var{b})} +@tab @code{MPACKH @var{a},@var{b},@var{c}} +@item @code{sw2 __MQADDHSS (sw2, sw2)} +@tab @code{@var{c} = __MQADDHSS (@var{a}, @var{b})} +@tab @code{MQADDHSS @var{a},@var{b},@var{c}} +@item @code{uw2 __MQADDHUS (uw2, uw2)} +@tab @code{@var{c} = __MQADDHUS (@var{a}, @var{b})} +@tab @code{MQADDHUS @var{a},@var{b},@var{c}} +@item @code{void __MQCPXIS (acc, sw2, sw2)} +@tab @code{__MQCPXIS (@var{c}, @var{a}, @var{b})} +@tab @code{MQCPXIS @var{a},@var{b},@var{c}} +@item @code{void __MQCPXIU (acc, uw2, uw2)} +@tab @code{__MQCPXIU (@var{c}, @var{a}, @var{b})} +@tab @code{MQCPXIU @var{a},@var{b},@var{c}} +@item @code{void __MQCPXRS (acc, sw2, sw2)} +@tab @code{__MQCPXRS (@var{c}, @var{a}, @var{b})} +@tab @code{MQCPXRS @var{a},@var{b},@var{c}} +@item @code{void __MQCPXRU (acc, uw2, uw2)} +@tab @code{__MQCPXRU (@var{c}, @var{a}, @var{b})} +@tab @code{MQCPXRU @var{a},@var{b},@var{c}} +@item @code{sw2 __MQLCLRHS (sw2, sw2)} +@tab @code{@var{c} = __MQLCLRHS (@var{a}, @var{b})} +@tab @code{MQLCLRHS @var{a},@var{b},@var{c}} +@item @code{sw2 __MQLMTHS (sw2, sw2)} +@tab @code{@var{c} = __MQLMTHS (@var{a}, @var{b})} +@tab @code{MQLMTHS @var{a},@var{b},@var{c}} +@item @code{void __MQMACHS (acc, sw2, sw2)} +@tab @code{__MQMACHS (@var{c}, @var{a}, @var{b})} +@tab @code{MQMACHS @var{a},@var{b},@var{c}} +@item @code{void __MQMACHU (acc, uw2, uw2)} +@tab @code{__MQMACHU (@var{c}, @var{a}, @var{b})} +@tab @code{MQMACHU @var{a},@var{b},@var{c}} +@item @code{void __MQMACXHS (acc, sw2, sw2)} +@tab @code{__MQMACXHS (@var{c}, @var{a}, @var{b})} +@tab @code{MQMACXHS @var{a},@var{b},@var{c}} +@item @code{void __MQMULHS (acc, sw2, sw2)} +@tab @code{__MQMULHS (@var{c}, @var{a}, @var{b})} +@tab @code{MQMULHS @var{a},@var{b},@var{c}} +@item @code{void __MQMULHU (acc, uw2, uw2)} +@tab @code{__MQMULHU (@var{c}, @var{a}, @var{b})} +@tab @code{MQMULHU @var{a},@var{b},@var{c}} +@item @code{void __MQMULXHS (acc, sw2, sw2)} +@tab @code{__MQMULXHS (@var{c}, @var{a}, @var{b})} +@tab @code{MQMULXHS @var{a},@var{b},@var{c}} +@item @code{void __MQMULXHU (acc, uw2, uw2)} +@tab @code{__MQMULXHU (@var{c}, @var{a}, @var{b})} +@tab @code{MQMULXHU @var{a},@var{b},@var{c}} +@item @code{sw2 __MQSATHS (sw2, sw2)} +@tab @code{@var{c} = __MQSATHS (@var{a}, @var{b})} +@tab @code{MQSATHS @var{a},@var{b},@var{c}} +@item @code{uw2 __MQSLLHI (uw2, int)} +@tab @code{@var{c} = __MQSLLHI (@var{a}, @var{b})} +@tab @code{MQSLLHI @var{a},@var{b},@var{c}} +@item @code{sw2 __MQSRAHI (sw2, int)} +@tab @code{@var{c} = __MQSRAHI (@var{a}, @var{b})} +@tab @code{MQSRAHI @var{a},@var{b},@var{c}} +@item @code{sw2 __MQSUBHSS (sw2, sw2)} +@tab @code{@var{c} = __MQSUBHSS (@var{a}, @var{b})} +@tab @code{MQSUBHSS @var{a},@var{b},@var{c}} +@item @code{uw2 __MQSUBHUS (uw2, uw2)} +@tab @code{@var{c} = __MQSUBHUS (@var{a}, @var{b})} +@tab @code{MQSUBHUS @var{a},@var{b},@var{c}} +@item @code{void __MQXMACHS (acc, sw2, sw2)} +@tab @code{__MQXMACHS (@var{c}, @var{a}, @var{b})} +@tab @code{MQXMACHS @var{a},@var{b},@var{c}} +@item @code{void __MQXMACXHS (acc, sw2, sw2)} +@tab @code{__MQXMACXHS (@var{c}, @var{a}, @var{b})} +@tab @code{MQXMACXHS @var{a},@var{b},@var{c}} +@item @code{uw1 __MRDACC (acc)} +@tab @code{@var{b} = __MRDACC (@var{a})} +@tab @code{MRDACC @var{a},@var{b}} +@item @code{uw1 __MRDACCG (acc)} +@tab @code{@var{b} = __MRDACCG (@var{a})} +@tab @code{MRDACCG @var{a},@var{b}} +@item @code{uw1 __MROTLI (uw1, const)} +@tab @code{@var{c} = __MROTLI (@var{a}, @var{b})} +@tab @code{MROTLI @var{a},#@var{b},@var{c}} +@item @code{uw1 __MROTRI (uw1, const)} +@tab @code{@var{c} = __MROTRI (@var{a}, @var{b})} +@tab @code{MROTRI @var{a},#@var{b},@var{c}} +@item @code{sw1 __MSATHS (sw1, sw1)} +@tab @code{@var{c} = __MSATHS (@var{a}, @var{b})} +@tab @code{MSATHS @var{a},@var{b},@var{c}} +@item @code{uw1 __MSATHU (uw1, uw1)} +@tab @code{@var{c} = __MSATHU (@var{a}, @var{b})} +@tab @code{MSATHU @var{a},@var{b},@var{c}} +@item @code{uw1 __MSLLHI (uw1, const)} +@tab @code{@var{c} = __MSLLHI (@var{a}, @var{b})} +@tab @code{MSLLHI @var{a},#@var{b},@var{c}} +@item @code{sw1 __MSRAHI (sw1, const)} +@tab @code{@var{c} = __MSRAHI (@var{a}, @var{b})} +@tab @code{MSRAHI @var{a},#@var{b},@var{c}} +@item @code{uw1 __MSRLHI (uw1, const)} +@tab @code{@var{c} = __MSRLHI (@var{a}, @var{b})} +@tab @code{MSRLHI @var{a},#@var{b},@var{c}} +@item @code{void __MSUBACCS (acc, acc)} +@tab @code{__MSUBACCS (@var{b}, @var{a})} +@tab @code{MSUBACCS @var{a},@var{b}} +@item @code{sw1 __MSUBHSS (sw1, sw1)} +@tab @code{@var{c} = __MSUBHSS (@var{a}, @var{b})} +@tab @code{MSUBHSS @var{a},@var{b},@var{c}} +@item @code{uw1 __MSUBHUS (uw1, uw1)} +@tab @code{@var{c} = __MSUBHUS (@var{a}, @var{b})} +@tab @code{MSUBHUS @var{a},@var{b},@var{c}} +@item @code{void __MTRAP (void)} +@tab @code{__MTRAP ()} +@tab @code{MTRAP} +@item @code{uw2 __MUNPACKH (uw1)} +@tab @code{@var{b} = __MUNPACKH (@var{a})} +@tab @code{MUNPACKH @var{a},@var{b}} +@item @code{uw1 __MWCUT (uw2, uw1)} +@tab @code{@var{c} = __MWCUT (@var{a}, @var{b})} +@tab @code{MWCUT @var{a},@var{b},@var{c}} +@item @code{void __MWTACC (acc, uw1)} +@tab @code{__MWTACC (@var{b}, @var{a})} +@tab @code{MWTACC @var{a},@var{b}} +@item @code{void __MWTACCG (acc, uw1)} +@tab @code{__MWTACCG (@var{b}, @var{a})} +@tab @code{MWTACCG @var{a},@var{b}} +@item @code{uw1 __MXOR (uw1, uw1)} +@tab @code{@var{c} = __MXOR (@var{a}, @var{b})} +@tab @code{MXOR @var{a},@var{b},@var{c}} +@end multitable + +@node Raw read/write Functions +@subsubsection Raw read/write Functions + +This sections describes built-in functions related to read and write +instructions to access memory. These functions generate +@code{membar} instructions to flush the I/O load and stores where +appropriate, as described in Fujitsu's manual described above. + +@table @code + +@item unsigned char __builtin_read8 (void *@var{data}) +@item unsigned short __builtin_read16 (void *@var{data}) +@item unsigned long __builtin_read32 (void *@var{data}) +@item unsigned long long __builtin_read64 (void *@var{data}) + +@item void __builtin_write8 (void *@var{data}, unsigned char @var{datum}) +@item void __builtin_write16 (void *@var{data}, unsigned short @var{datum}) +@item void __builtin_write32 (void *@var{data}, unsigned long @var{datum}) +@item void __builtin_write64 (void *@var{data}, unsigned long long @var{datum}) +@end table + +@node Other Built-in Functions +@subsubsection Other Built-in Functions + +This section describes built-in functions that are not named after +a specific FR-V instruction. + +@table @code +@item sw2 __IACCreadll (iacc @var{reg}) +Return the full 64-bit value of IACC0@. The @var{reg} argument is reserved +for future expansion and must be 0. + +@item sw1 __IACCreadl (iacc @var{reg}) +Return the value of IACC0H if @var{reg} is 0 and IACC0L if @var{reg} is 1. +Other values of @var{reg} are rejected as invalid. + +@item void __IACCsetll (iacc @var{reg}, sw2 @var{x}) +Set the full 64-bit value of IACC0 to @var{x}. The @var{reg} argument +is reserved for future expansion and must be 0. + +@item void __IACCsetl (iacc @var{reg}, sw1 @var{x}) +Set IACC0H to @var{x} if @var{reg} is 0 and IACC0L to @var{x} if @var{reg} +is 1. Other values of @var{reg} are rejected as invalid. + +@item void __data_prefetch0 (const void *@var{x}) +Use the @code{dcpl} instruction to load the contents of address @var{x} +into the data cache. + +@item void __data_prefetch (const void *@var{x}) +Use the @code{nldub} instruction to load the contents of address @var{x} +into the data cache. The instruction will be issued in slot I1@. +@end table + +@node X86 Built-in Functions +@subsection X86 Built-in Functions + +These built-in functions are available for the i386 and x86-64 family +of computers, depending on the command-line switches used. + +Note that, if you specify command-line switches such as @option{-msse}, +the compiler could use the extended instruction sets even if the built-ins +are not used explicitly in the program. For this reason, applications +which perform runtime CPU detection must compile separate files for each +supported architecture, using the appropriate flags. In particular, +the file containing the CPU detection code should be compiled without +these options. + +The following machine modes are available for use with MMX built-in functions +(@pxref{Vector Extensions}): @code{V2SI} for a vector of two 32-bit integers, +@code{V4HI} for a vector of four 16-bit integers, and @code{V8QI} for a +vector of eight 8-bit integers. Some of the built-in functions operate on +MMX registers as a whole 64-bit entity, these use @code{V1DI} as their mode. + +If 3DNow!@: extensions are enabled, @code{V2SF} is used as a mode for a vector +of two 32-bit floating point values. + +If SSE extensions are enabled, @code{V4SF} is used for a vector of four 32-bit +floating point values. Some instructions use a vector of four 32-bit +integers, these use @code{V4SI}. Finally, some instructions operate on an +entire vector register, interpreting it as a 128-bit integer, these use mode +@code{TI}. + +In 64-bit mode, the x86-64 family of processors uses additional built-in +functions for efficient use of @code{TF} (@code{__float128}) 128-bit +floating point and @code{TC} 128-bit complex floating point values. + +The following floating point built-in functions are available in 64-bit +mode. All of them implement the function that is part of the name. + +@smallexample +__float128 __builtin_fabsq (__float128) +__float128 __builtin_copysignq (__float128, __float128) +@end smallexample + +The following floating point built-in functions are made available in the +64-bit mode. + +@table @code +@item __float128 __builtin_infq (void) +Similar to @code{__builtin_inf}, except the return type is @code{__float128}. +@findex __builtin_infq + +@item __float128 __builtin_huge_valq (void) +Similar to @code{__builtin_huge_val}, except the return type is @code{__float128}. +@findex __builtin_huge_valq +@end table + +The following built-in functions are made available by @option{-mmmx}. +All of them generate the machine instruction that is part of the name. + +@smallexample +v8qi __builtin_ia32_paddb (v8qi, v8qi) +v4hi __builtin_ia32_paddw (v4hi, v4hi) +v2si __builtin_ia32_paddd (v2si, v2si) +v8qi __builtin_ia32_psubb (v8qi, v8qi) +v4hi __builtin_ia32_psubw (v4hi, v4hi) +v2si __builtin_ia32_psubd (v2si, v2si) +v8qi __builtin_ia32_paddsb (v8qi, v8qi) +v4hi __builtin_ia32_paddsw (v4hi, v4hi) +v8qi __builtin_ia32_psubsb (v8qi, v8qi) +v4hi __builtin_ia32_psubsw (v4hi, v4hi) +v8qi __builtin_ia32_paddusb (v8qi, v8qi) +v4hi __builtin_ia32_paddusw (v4hi, v4hi) +v8qi __builtin_ia32_psubusb (v8qi, v8qi) +v4hi __builtin_ia32_psubusw (v4hi, v4hi) +v4hi __builtin_ia32_pmullw (v4hi, v4hi) +v4hi __builtin_ia32_pmulhw (v4hi, v4hi) +di __builtin_ia32_pand (di, di) +di __builtin_ia32_pandn (di,di) +di __builtin_ia32_por (di, di) +di __builtin_ia32_pxor (di, di) +v8qi __builtin_ia32_pcmpeqb (v8qi, v8qi) +v4hi __builtin_ia32_pcmpeqw (v4hi, v4hi) +v2si __builtin_ia32_pcmpeqd (v2si, v2si) +v8qi __builtin_ia32_pcmpgtb (v8qi, v8qi) +v4hi __builtin_ia32_pcmpgtw (v4hi, v4hi) +v2si __builtin_ia32_pcmpgtd (v2si, v2si) +v8qi __builtin_ia32_punpckhbw (v8qi, v8qi) +v4hi __builtin_ia32_punpckhwd (v4hi, v4hi) +v2si __builtin_ia32_punpckhdq (v2si, v2si) +v8qi __builtin_ia32_punpcklbw (v8qi, v8qi) +v4hi __builtin_ia32_punpcklwd (v4hi, v4hi) +v2si __builtin_ia32_punpckldq (v2si, v2si) +v8qi __builtin_ia32_packsswb (v4hi, v4hi) +v4hi __builtin_ia32_packssdw (v2si, v2si) +v8qi __builtin_ia32_packuswb (v4hi, v4hi) + +v4hi __builtin_ia32_psllw (v4hi, v4hi) +v2si __builtin_ia32_pslld (v2si, v2si) +v1di __builtin_ia32_psllq (v1di, v1di) +v4hi __builtin_ia32_psrlw (v4hi, v4hi) +v2si __builtin_ia32_psrld (v2si, v2si) +v1di __builtin_ia32_psrlq (v1di, v1di) +v4hi __builtin_ia32_psraw (v4hi, v4hi) +v2si __builtin_ia32_psrad (v2si, v2si) +v4hi __builtin_ia32_psllwi (v4hi, int) +v2si __builtin_ia32_pslldi (v2si, int) +v1di __builtin_ia32_psllqi (v1di, int) +v4hi __builtin_ia32_psrlwi (v4hi, int) +v2si __builtin_ia32_psrldi (v2si, int) +v1di __builtin_ia32_psrlqi (v1di, int) +v4hi __builtin_ia32_psrawi (v4hi, int) +v2si __builtin_ia32_psradi (v2si, int) + +@end smallexample + +The following built-in functions are made available either with +@option{-msse}, or with a combination of @option{-m3dnow} and +@option{-march=athlon}. All of them generate the machine +instruction that is part of the name. + +@smallexample +v4hi __builtin_ia32_pmulhuw (v4hi, v4hi) +v8qi __builtin_ia32_pavgb (v8qi, v8qi) +v4hi __builtin_ia32_pavgw (v4hi, v4hi) +v1di __builtin_ia32_psadbw (v8qi, v8qi) +v8qi __builtin_ia32_pmaxub (v8qi, v8qi) +v4hi __builtin_ia32_pmaxsw (v4hi, v4hi) +v8qi __builtin_ia32_pminub (v8qi, v8qi) +v4hi __builtin_ia32_pminsw (v4hi, v4hi) +int __builtin_ia32_pextrw (v4hi, int) +v4hi __builtin_ia32_pinsrw (v4hi, int, int) +int __builtin_ia32_pmovmskb (v8qi) +void __builtin_ia32_maskmovq (v8qi, v8qi, char *) +void __builtin_ia32_movntq (di *, di) +void __builtin_ia32_sfence (void) +@end smallexample + +The following built-in functions are available when @option{-msse} is used. +All of them generate the machine instruction that is part of the name. + +@smallexample +int __builtin_ia32_comieq (v4sf, v4sf) +int __builtin_ia32_comineq (v4sf, v4sf) +int __builtin_ia32_comilt (v4sf, v4sf) +int __builtin_ia32_comile (v4sf, v4sf) +int __builtin_ia32_comigt (v4sf, v4sf) +int __builtin_ia32_comige (v4sf, v4sf) +int __builtin_ia32_ucomieq (v4sf, v4sf) +int __builtin_ia32_ucomineq (v4sf, v4sf) +int __builtin_ia32_ucomilt (v4sf, v4sf) +int __builtin_ia32_ucomile (v4sf, v4sf) +int __builtin_ia32_ucomigt (v4sf, v4sf) +int __builtin_ia32_ucomige (v4sf, v4sf) +v4sf __builtin_ia32_addps (v4sf, v4sf) +v4sf __builtin_ia32_subps (v4sf, v4sf) +v4sf __builtin_ia32_mulps (v4sf, v4sf) +v4sf __builtin_ia32_divps (v4sf, v4sf) +v4sf __builtin_ia32_addss (v4sf, v4sf) +v4sf __builtin_ia32_subss (v4sf, v4sf) +v4sf __builtin_ia32_mulss (v4sf, v4sf) +v4sf __builtin_ia32_divss (v4sf, v4sf) +v4si __builtin_ia32_cmpeqps (v4sf, v4sf) +v4si __builtin_ia32_cmpltps (v4sf, v4sf) +v4si __builtin_ia32_cmpleps (v4sf, v4sf) +v4si __builtin_ia32_cmpgtps (v4sf, v4sf) +v4si __builtin_ia32_cmpgeps (v4sf, v4sf) +v4si __builtin_ia32_cmpunordps (v4sf, v4sf) +v4si __builtin_ia32_cmpneqps (v4sf, v4sf) +v4si __builtin_ia32_cmpnltps (v4sf, v4sf) +v4si __builtin_ia32_cmpnleps (v4sf, v4sf) +v4si __builtin_ia32_cmpngtps (v4sf, v4sf) +v4si __builtin_ia32_cmpngeps (v4sf, v4sf) +v4si __builtin_ia32_cmpordps (v4sf, v4sf) +v4si __builtin_ia32_cmpeqss (v4sf, v4sf) +v4si __builtin_ia32_cmpltss (v4sf, v4sf) +v4si __builtin_ia32_cmpless (v4sf, v4sf) +v4si __builtin_ia32_cmpunordss (v4sf, v4sf) +v4si __builtin_ia32_cmpneqss (v4sf, v4sf) +v4si __builtin_ia32_cmpnlts (v4sf, v4sf) +v4si __builtin_ia32_cmpnless (v4sf, v4sf) +v4si __builtin_ia32_cmpordss (v4sf, v4sf) +v4sf __builtin_ia32_maxps (v4sf, v4sf) +v4sf __builtin_ia32_maxss (v4sf, v4sf) +v4sf __builtin_ia32_minps (v4sf, v4sf) +v4sf __builtin_ia32_minss (v4sf, v4sf) +v4sf __builtin_ia32_andps (v4sf, v4sf) +v4sf __builtin_ia32_andnps (v4sf, v4sf) +v4sf __builtin_ia32_orps (v4sf, v4sf) +v4sf __builtin_ia32_xorps (v4sf, v4sf) +v4sf __builtin_ia32_movss (v4sf, v4sf) +v4sf __builtin_ia32_movhlps (v4sf, v4sf) +v4sf __builtin_ia32_movlhps (v4sf, v4sf) +v4sf __builtin_ia32_unpckhps (v4sf, v4sf) +v4sf __builtin_ia32_unpcklps (v4sf, v4sf) +v4sf __builtin_ia32_cvtpi2ps (v4sf, v2si) +v4sf __builtin_ia32_cvtsi2ss (v4sf, int) +v2si __builtin_ia32_cvtps2pi (v4sf) +int __builtin_ia32_cvtss2si (v4sf) +v2si __builtin_ia32_cvttps2pi (v4sf) +int __builtin_ia32_cvttss2si (v4sf) +v4sf __builtin_ia32_rcpps (v4sf) +v4sf __builtin_ia32_rsqrtps (v4sf) +v4sf __builtin_ia32_sqrtps (v4sf) +v4sf __builtin_ia32_rcpss (v4sf) +v4sf __builtin_ia32_rsqrtss (v4sf) +v4sf __builtin_ia32_sqrtss (v4sf) +v4sf __builtin_ia32_shufps (v4sf, v4sf, int) +void __builtin_ia32_movntps (float *, v4sf) +int __builtin_ia32_movmskps (v4sf) +@end smallexample + +The following built-in functions are available when @option{-msse} is used. + +@table @code +@item v4sf __builtin_ia32_loadaps (float *) +Generates the @code{movaps} machine instruction as a load from memory. +@item void __builtin_ia32_storeaps (float *, v4sf) +Generates the @code{movaps} machine instruction as a store to memory. +@item v4sf __builtin_ia32_loadups (float *) +Generates the @code{movups} machine instruction as a load from memory. +@item void __builtin_ia32_storeups (float *, v4sf) +Generates the @code{movups} machine instruction as a store to memory. +@item v4sf __builtin_ia32_loadsss (float *) +Generates the @code{movss} machine instruction as a load from memory. +@item void __builtin_ia32_storess (float *, v4sf) +Generates the @code{movss} machine instruction as a store to memory. +@item v4sf __builtin_ia32_loadhps (v4sf, const v2sf *) +Generates the @code{movhps} machine instruction as a load from memory. +@item v4sf __builtin_ia32_loadlps (v4sf, const v2sf *) +Generates the @code{movlps} machine instruction as a load from memory +@item void __builtin_ia32_storehps (v2sf *, v4sf) +Generates the @code{movhps} machine instruction as a store to memory. +@item void __builtin_ia32_storelps (v2sf *, v4sf) +Generates the @code{movlps} machine instruction as a store to memory. +@end table + +The following built-in functions are available when @option{-msse2} is used. +All of them generate the machine instruction that is part of the name. + +@smallexample +int __builtin_ia32_comisdeq (v2df, v2df) +int __builtin_ia32_comisdlt (v2df, v2df) +int __builtin_ia32_comisdle (v2df, v2df) +int __builtin_ia32_comisdgt (v2df, v2df) +int __builtin_ia32_comisdge (v2df, v2df) +int __builtin_ia32_comisdneq (v2df, v2df) +int __builtin_ia32_ucomisdeq (v2df, v2df) +int __builtin_ia32_ucomisdlt (v2df, v2df) +int __builtin_ia32_ucomisdle (v2df, v2df) +int __builtin_ia32_ucomisdgt (v2df, v2df) +int __builtin_ia32_ucomisdge (v2df, v2df) +int __builtin_ia32_ucomisdneq (v2df, v2df) +v2df __builtin_ia32_cmpeqpd (v2df, v2df) +v2df __builtin_ia32_cmpltpd (v2df, v2df) +v2df __builtin_ia32_cmplepd (v2df, v2df) +v2df __builtin_ia32_cmpgtpd (v2df, v2df) +v2df __builtin_ia32_cmpgepd (v2df, v2df) +v2df __builtin_ia32_cmpunordpd (v2df, v2df) +v2df __builtin_ia32_cmpneqpd (v2df, v2df) +v2df __builtin_ia32_cmpnltpd (v2df, v2df) +v2df __builtin_ia32_cmpnlepd (v2df, v2df) +v2df __builtin_ia32_cmpngtpd (v2df, v2df) +v2df __builtin_ia32_cmpngepd (v2df, v2df) +v2df __builtin_ia32_cmpordpd (v2df, v2df) +v2df __builtin_ia32_cmpeqsd (v2df, v2df) +v2df __builtin_ia32_cmpltsd (v2df, v2df) +v2df __builtin_ia32_cmplesd (v2df, v2df) +v2df __builtin_ia32_cmpunordsd (v2df, v2df) +v2df __builtin_ia32_cmpneqsd (v2df, v2df) +v2df __builtin_ia32_cmpnltsd (v2df, v2df) +v2df __builtin_ia32_cmpnlesd (v2df, v2df) +v2df __builtin_ia32_cmpordsd (v2df, v2df) +v2di __builtin_ia32_paddq (v2di, v2di) +v2di __builtin_ia32_psubq (v2di, v2di) +v2df __builtin_ia32_addpd (v2df, v2df) +v2df __builtin_ia32_subpd (v2df, v2df) +v2df __builtin_ia32_mulpd (v2df, v2df) +v2df __builtin_ia32_divpd (v2df, v2df) +v2df __builtin_ia32_addsd (v2df, v2df) +v2df __builtin_ia32_subsd (v2df, v2df) +v2df __builtin_ia32_mulsd (v2df, v2df) +v2df __builtin_ia32_divsd (v2df, v2df) +v2df __builtin_ia32_minpd (v2df, v2df) +v2df __builtin_ia32_maxpd (v2df, v2df) +v2df __builtin_ia32_minsd (v2df, v2df) +v2df __builtin_ia32_maxsd (v2df, v2df) +v2df __builtin_ia32_andpd (v2df, v2df) +v2df __builtin_ia32_andnpd (v2df, v2df) +v2df __builtin_ia32_orpd (v2df, v2df) +v2df __builtin_ia32_xorpd (v2df, v2df) +v2df __builtin_ia32_movsd (v2df, v2df) +v2df __builtin_ia32_unpckhpd (v2df, v2df) +v2df __builtin_ia32_unpcklpd (v2df, v2df) +v16qi __builtin_ia32_paddb128 (v16qi, v16qi) +v8hi __builtin_ia32_paddw128 (v8hi, v8hi) +v4si __builtin_ia32_paddd128 (v4si, v4si) +v2di __builtin_ia32_paddq128 (v2di, v2di) +v16qi __builtin_ia32_psubb128 (v16qi, v16qi) +v8hi __builtin_ia32_psubw128 (v8hi, v8hi) +v4si __builtin_ia32_psubd128 (v4si, v4si) +v2di __builtin_ia32_psubq128 (v2di, v2di) +v8hi __builtin_ia32_pmullw128 (v8hi, v8hi) +v8hi __builtin_ia32_pmulhw128 (v8hi, v8hi) +v2di __builtin_ia32_pand128 (v2di, v2di) +v2di __builtin_ia32_pandn128 (v2di, v2di) +v2di __builtin_ia32_por128 (v2di, v2di) +v2di __builtin_ia32_pxor128 (v2di, v2di) +v16qi __builtin_ia32_pavgb128 (v16qi, v16qi) +v8hi __builtin_ia32_pavgw128 (v8hi, v8hi) +v16qi __builtin_ia32_pcmpeqb128 (v16qi, v16qi) +v8hi __builtin_ia32_pcmpeqw128 (v8hi, v8hi) +v4si __builtin_ia32_pcmpeqd128 (v4si, v4si) +v16qi __builtin_ia32_pcmpgtb128 (v16qi, v16qi) +v8hi __builtin_ia32_pcmpgtw128 (v8hi, v8hi) +v4si __builtin_ia32_pcmpgtd128 (v4si, v4si) +v16qi __builtin_ia32_pmaxub128 (v16qi, v16qi) +v8hi __builtin_ia32_pmaxsw128 (v8hi, v8hi) +v16qi __builtin_ia32_pminub128 (v16qi, v16qi) +v8hi __builtin_ia32_pminsw128 (v8hi, v8hi) +v16qi __builtin_ia32_punpckhbw128 (v16qi, v16qi) +v8hi __builtin_ia32_punpckhwd128 (v8hi, v8hi) +v4si __builtin_ia32_punpckhdq128 (v4si, v4si) +v2di __builtin_ia32_punpckhqdq128 (v2di, v2di) +v16qi __builtin_ia32_punpcklbw128 (v16qi, v16qi) +v8hi __builtin_ia32_punpcklwd128 (v8hi, v8hi) +v4si __builtin_ia32_punpckldq128 (v4si, v4si) +v2di __builtin_ia32_punpcklqdq128 (v2di, v2di) +v16qi __builtin_ia32_packsswb128 (v8hi, v8hi) +v8hi __builtin_ia32_packssdw128 (v4si, v4si) +v16qi __builtin_ia32_packuswb128 (v8hi, v8hi) +v8hi __builtin_ia32_pmulhuw128 (v8hi, v8hi) +void __builtin_ia32_maskmovdqu (v16qi, v16qi) +v2df __builtin_ia32_loadupd (double *) +void __builtin_ia32_storeupd (double *, v2df) +v2df __builtin_ia32_loadhpd (v2df, double const *) +v2df __builtin_ia32_loadlpd (v2df, double const *) +int __builtin_ia32_movmskpd (v2df) +int __builtin_ia32_pmovmskb128 (v16qi) +void __builtin_ia32_movnti (int *, int) +void __builtin_ia32_movntpd (double *, v2df) +void __builtin_ia32_movntdq (v2df *, v2df) +v4si __builtin_ia32_pshufd (v4si, int) +v8hi __builtin_ia32_pshuflw (v8hi, int) +v8hi __builtin_ia32_pshufhw (v8hi, int) +v2di __builtin_ia32_psadbw128 (v16qi, v16qi) +v2df __builtin_ia32_sqrtpd (v2df) +v2df __builtin_ia32_sqrtsd (v2df) +v2df __builtin_ia32_shufpd (v2df, v2df, int) +v2df __builtin_ia32_cvtdq2pd (v4si) +v4sf __builtin_ia32_cvtdq2ps (v4si) +v4si __builtin_ia32_cvtpd2dq (v2df) +v2si __builtin_ia32_cvtpd2pi (v2df) +v4sf __builtin_ia32_cvtpd2ps (v2df) +v4si __builtin_ia32_cvttpd2dq (v2df) +v2si __builtin_ia32_cvttpd2pi (v2df) +v2df __builtin_ia32_cvtpi2pd (v2si) +int __builtin_ia32_cvtsd2si (v2df) +int __builtin_ia32_cvttsd2si (v2df) +long long __builtin_ia32_cvtsd2si64 (v2df) +long long __builtin_ia32_cvttsd2si64 (v2df) +v4si __builtin_ia32_cvtps2dq (v4sf) +v2df __builtin_ia32_cvtps2pd (v4sf) +v4si __builtin_ia32_cvttps2dq (v4sf) +v2df __builtin_ia32_cvtsi2sd (v2df, int) +v2df __builtin_ia32_cvtsi642sd (v2df, long long) +v4sf __builtin_ia32_cvtsd2ss (v4sf, v2df) +v2df __builtin_ia32_cvtss2sd (v2df, v4sf) +void __builtin_ia32_clflush (const void *) +void __builtin_ia32_lfence (void) +void __builtin_ia32_mfence (void) +v16qi __builtin_ia32_loaddqu (const char *) +void __builtin_ia32_storedqu (char *, v16qi) +v1di __builtin_ia32_pmuludq (v2si, v2si) +v2di __builtin_ia32_pmuludq128 (v4si, v4si) +v8hi __builtin_ia32_psllw128 (v8hi, v8hi) +v4si __builtin_ia32_pslld128 (v4si, v4si) +v2di __builtin_ia32_psllq128 (v2di, v2di) +v8hi __builtin_ia32_psrlw128 (v8hi, v8hi) +v4si __builtin_ia32_psrld128 (v4si, v4si) +v2di __builtin_ia32_psrlq128 (v2di, v2di) +v8hi __builtin_ia32_psraw128 (v8hi, v8hi) +v4si __builtin_ia32_psrad128 (v4si, v4si) +v2di __builtin_ia32_pslldqi128 (v2di, int) +v8hi __builtin_ia32_psllwi128 (v8hi, int) +v4si __builtin_ia32_pslldi128 (v4si, int) +v2di __builtin_ia32_psllqi128 (v2di, int) +v2di __builtin_ia32_psrldqi128 (v2di, int) +v8hi __builtin_ia32_psrlwi128 (v8hi, int) +v4si __builtin_ia32_psrldi128 (v4si, int) +v2di __builtin_ia32_psrlqi128 (v2di, int) +v8hi __builtin_ia32_psrawi128 (v8hi, int) +v4si __builtin_ia32_psradi128 (v4si, int) +v4si __builtin_ia32_pmaddwd128 (v8hi, v8hi) +v2di __builtin_ia32_movq128 (v2di) +@end smallexample + +The following built-in functions are available when @option{-msse3} is used. +All of them generate the machine instruction that is part of the name. + +@smallexample +v2df __builtin_ia32_addsubpd (v2df, v2df) +v4sf __builtin_ia32_addsubps (v4sf, v4sf) +v2df __builtin_ia32_haddpd (v2df, v2df) +v4sf __builtin_ia32_haddps (v4sf, v4sf) +v2df __builtin_ia32_hsubpd (v2df, v2df) +v4sf __builtin_ia32_hsubps (v4sf, v4sf) +v16qi __builtin_ia32_lddqu (char const *) +void __builtin_ia32_monitor (void *, unsigned int, unsigned int) +v2df __builtin_ia32_movddup (v2df) +v4sf __builtin_ia32_movshdup (v4sf) +v4sf __builtin_ia32_movsldup (v4sf) +void __builtin_ia32_mwait (unsigned int, unsigned int) +@end smallexample + +The following built-in functions are available when @option{-msse3} is used. + +@table @code +@item v2df __builtin_ia32_loadddup (double const *) +Generates the @code{movddup} machine instruction as a load from memory. +@end table + +The following built-in functions are available when @option{-mssse3} is used. +All of them generate the machine instruction that is part of the name +with MMX registers. + +@smallexample +v2si __builtin_ia32_phaddd (v2si, v2si) +v4hi __builtin_ia32_phaddw (v4hi, v4hi) +v4hi __builtin_ia32_phaddsw (v4hi, v4hi) +v2si __builtin_ia32_phsubd (v2si, v2si) +v4hi __builtin_ia32_phsubw (v4hi, v4hi) +v4hi __builtin_ia32_phsubsw (v4hi, v4hi) +v4hi __builtin_ia32_pmaddubsw (v8qi, v8qi) +v4hi __builtin_ia32_pmulhrsw (v4hi, v4hi) +v8qi __builtin_ia32_pshufb (v8qi, v8qi) +v8qi __builtin_ia32_psignb (v8qi, v8qi) +v2si __builtin_ia32_psignd (v2si, v2si) +v4hi __builtin_ia32_psignw (v4hi, v4hi) +v1di __builtin_ia32_palignr (v1di, v1di, int) +v8qi __builtin_ia32_pabsb (v8qi) +v2si __builtin_ia32_pabsd (v2si) +v4hi __builtin_ia32_pabsw (v4hi) +@end smallexample + +The following built-in functions are available when @option{-mssse3} is used. +All of them generate the machine instruction that is part of the name +with SSE registers. + +@smallexample +v4si __builtin_ia32_phaddd128 (v4si, v4si) +v8hi __builtin_ia32_phaddw128 (v8hi, v8hi) +v8hi __builtin_ia32_phaddsw128 (v8hi, v8hi) +v4si __builtin_ia32_phsubd128 (v4si, v4si) +v8hi __builtin_ia32_phsubw128 (v8hi, v8hi) +v8hi __builtin_ia32_phsubsw128 (v8hi, v8hi) +v8hi __builtin_ia32_pmaddubsw128 (v16qi, v16qi) +v8hi __builtin_ia32_pmulhrsw128 (v8hi, v8hi) +v16qi __builtin_ia32_pshufb128 (v16qi, v16qi) +v16qi __builtin_ia32_psignb128 (v16qi, v16qi) +v4si __builtin_ia32_psignd128 (v4si, v4si) +v8hi __builtin_ia32_psignw128 (v8hi, v8hi) +v2di __builtin_ia32_palignr128 (v2di, v2di, int) +v16qi __builtin_ia32_pabsb128 (v16qi) +v4si __builtin_ia32_pabsd128 (v4si) +v8hi __builtin_ia32_pabsw128 (v8hi) +@end smallexample + +The following built-in functions are available when @option{-msse4.1} is +used. All of them generate the machine instruction that is part of the +name. + +@smallexample +v2df __builtin_ia32_blendpd (v2df, v2df, const int) +v4sf __builtin_ia32_blendps (v4sf, v4sf, const int) +v2df __builtin_ia32_blendvpd (v2df, v2df, v2df) +v4sf __builtin_ia32_blendvps (v4sf, v4sf, v4sf) +v2df __builtin_ia32_dppd (v2df, v2df, const int) +v4sf __builtin_ia32_dpps (v4sf, v4sf, const int) +v4sf __builtin_ia32_insertps128 (v4sf, v4sf, const int) +v2di __builtin_ia32_movntdqa (v2di *); +v16qi __builtin_ia32_mpsadbw128 (v16qi, v16qi, const int) +v8hi __builtin_ia32_packusdw128 (v4si, v4si) +v16qi __builtin_ia32_pblendvb128 (v16qi, v16qi, v16qi) +v8hi __builtin_ia32_pblendw128 (v8hi, v8hi, const int) +v2di __builtin_ia32_pcmpeqq (v2di, v2di) +v8hi __builtin_ia32_phminposuw128 (v8hi) +v16qi __builtin_ia32_pmaxsb128 (v16qi, v16qi) +v4si __builtin_ia32_pmaxsd128 (v4si, v4si) +v4si __builtin_ia32_pmaxud128 (v4si, v4si) +v8hi __builtin_ia32_pmaxuw128 (v8hi, v8hi) +v16qi __builtin_ia32_pminsb128 (v16qi, v16qi) +v4si __builtin_ia32_pminsd128 (v4si, v4si) +v4si __builtin_ia32_pminud128 (v4si, v4si) +v8hi __builtin_ia32_pminuw128 (v8hi, v8hi) +v4si __builtin_ia32_pmovsxbd128 (v16qi) +v2di __builtin_ia32_pmovsxbq128 (v16qi) +v8hi __builtin_ia32_pmovsxbw128 (v16qi) +v2di __builtin_ia32_pmovsxdq128 (v4si) +v4si __builtin_ia32_pmovsxwd128 (v8hi) +v2di __builtin_ia32_pmovsxwq128 (v8hi) +v4si __builtin_ia32_pmovzxbd128 (v16qi) +v2di __builtin_ia32_pmovzxbq128 (v16qi) +v8hi __builtin_ia32_pmovzxbw128 (v16qi) +v2di __builtin_ia32_pmovzxdq128 (v4si) +v4si __builtin_ia32_pmovzxwd128 (v8hi) +v2di __builtin_ia32_pmovzxwq128 (v8hi) +v2di __builtin_ia32_pmuldq128 (v4si, v4si) +v4si __builtin_ia32_pmulld128 (v4si, v4si) +int __builtin_ia32_ptestc128 (v2di, v2di) +int __builtin_ia32_ptestnzc128 (v2di, v2di) +int __builtin_ia32_ptestz128 (v2di, v2di) +v2df __builtin_ia32_roundpd (v2df, const int) +v4sf __builtin_ia32_roundps (v4sf, const int) +v2df __builtin_ia32_roundsd (v2df, v2df, const int) +v4sf __builtin_ia32_roundss (v4sf, v4sf, const int) +@end smallexample + +The following built-in functions are available when @option{-msse4.1} is +used. + +@table @code +@item v4sf __builtin_ia32_vec_set_v4sf (v4sf, float, const int) +Generates the @code{insertps} machine instruction. +@item int __builtin_ia32_vec_ext_v16qi (v16qi, const int) +Generates the @code{pextrb} machine instruction. +@item v16qi __builtin_ia32_vec_set_v16qi (v16qi, int, const int) +Generates the @code{pinsrb} machine instruction. +@item v4si __builtin_ia32_vec_set_v4si (v4si, int, const int) +Generates the @code{pinsrd} machine instruction. +@item v2di __builtin_ia32_vec_set_v2di (v2di, long long, const int) +Generates the @code{pinsrq} machine instruction in 64bit mode. +@end table + +The following built-in functions are changed to generate new SSE4.1 +instructions when @option{-msse4.1} is used. + +@table @code +@item float __builtin_ia32_vec_ext_v4sf (v4sf, const int) +Generates the @code{extractps} machine instruction. +@item int __builtin_ia32_vec_ext_v4si (v4si, const int) +Generates the @code{pextrd} machine instruction. +@item long long __builtin_ia32_vec_ext_v2di (v2di, const int) +Generates the @code{pextrq} machine instruction in 64bit mode. +@end table + +The following built-in functions are available when @option{-msse4.2} is +used. All of them generate the machine instruction that is part of the +name. + +@smallexample +v16qi __builtin_ia32_pcmpestrm128 (v16qi, int, v16qi, int, const int) +int __builtin_ia32_pcmpestri128 (v16qi, int, v16qi, int, const int) +int __builtin_ia32_pcmpestria128 (v16qi, int, v16qi, int, const int) +int __builtin_ia32_pcmpestric128 (v16qi, int, v16qi, int, const int) +int __builtin_ia32_pcmpestrio128 (v16qi, int, v16qi, int, const int) +int __builtin_ia32_pcmpestris128 (v16qi, int, v16qi, int, const int) +int __builtin_ia32_pcmpestriz128 (v16qi, int, v16qi, int, const int) +v16qi __builtin_ia32_pcmpistrm128 (v16qi, v16qi, const int) +int __builtin_ia32_pcmpistri128 (v16qi, v16qi, const int) +int __builtin_ia32_pcmpistria128 (v16qi, v16qi, const int) +int __builtin_ia32_pcmpistric128 (v16qi, v16qi, const int) +int __builtin_ia32_pcmpistrio128 (v16qi, v16qi, const int) +int __builtin_ia32_pcmpistris128 (v16qi, v16qi, const int) +int __builtin_ia32_pcmpistriz128 (v16qi, v16qi, const int) +v2di __builtin_ia32_pcmpgtq (v2di, v2di) +@end smallexample + +The following built-in functions are available when @option{-msse4.2} is +used. + +@table @code +@item unsigned int __builtin_ia32_crc32qi (unsigned int, unsigned char) +Generates the @code{crc32b} machine instruction. +@item unsigned int __builtin_ia32_crc32hi (unsigned int, unsigned short) +Generates the @code{crc32w} machine instruction. +@item unsigned int __builtin_ia32_crc32si (unsigned int, unsigned int) +Generates the @code{crc32l} machine instruction. +@item unsigned long long __builtin_ia32_crc32di (unsigned long long, unsigned long long) +Generates the @code{crc32q} machine instruction. +@end table + +The following built-in functions are changed to generate new SSE4.2 +instructions when @option{-msse4.2} is used. + +@table @code +@item int __builtin_popcount (unsigned int) +Generates the @code{popcntl} machine instruction. +@item int __builtin_popcountl (unsigned long) +Generates the @code{popcntl} or @code{popcntq} machine instruction, +depending on the size of @code{unsigned long}. +@item int __builtin_popcountll (unsigned long long) +Generates the @code{popcntq} machine instruction. +@end table + +The following built-in functions are available when @option{-mavx} is +used. All of them generate the machine instruction that is part of the +name. + +@smallexample +v4df __builtin_ia32_addpd256 (v4df,v4df) +v8sf __builtin_ia32_addps256 (v8sf,v8sf) +v4df __builtin_ia32_addsubpd256 (v4df,v4df) +v8sf __builtin_ia32_addsubps256 (v8sf,v8sf) +v4df __builtin_ia32_andnpd256 (v4df,v4df) +v8sf __builtin_ia32_andnps256 (v8sf,v8sf) +v4df __builtin_ia32_andpd256 (v4df,v4df) +v8sf __builtin_ia32_andps256 (v8sf,v8sf) +v4df __builtin_ia32_blendpd256 (v4df,v4df,int) +v8sf __builtin_ia32_blendps256 (v8sf,v8sf,int) +v4df __builtin_ia32_blendvpd256 (v4df,v4df,v4df) +v8sf __builtin_ia32_blendvps256 (v8sf,v8sf,v8sf) +v2df __builtin_ia32_cmppd (v2df,v2df,int) +v4df __builtin_ia32_cmppd256 (v4df,v4df,int) +v4sf __builtin_ia32_cmpps (v4sf,v4sf,int) +v8sf __builtin_ia32_cmpps256 (v8sf,v8sf,int) +v2df __builtin_ia32_cmpsd (v2df,v2df,int) +v4sf __builtin_ia32_cmpss (v4sf,v4sf,int) +v4df __builtin_ia32_cvtdq2pd256 (v4si) +v8sf __builtin_ia32_cvtdq2ps256 (v8si) +v4si __builtin_ia32_cvtpd2dq256 (v4df) +v4sf __builtin_ia32_cvtpd2ps256 (v4df) +v8si __builtin_ia32_cvtps2dq256 (v8sf) +v4df __builtin_ia32_cvtps2pd256 (v4sf) +v4si __builtin_ia32_cvttpd2dq256 (v4df) +v8si __builtin_ia32_cvttps2dq256 (v8sf) +v4df __builtin_ia32_divpd256 (v4df,v4df) +v8sf __builtin_ia32_divps256 (v8sf,v8sf) +v8sf __builtin_ia32_dpps256 (v8sf,v8sf,int) +v4df __builtin_ia32_haddpd256 (v4df,v4df) +v8sf __builtin_ia32_haddps256 (v8sf,v8sf) +v4df __builtin_ia32_hsubpd256 (v4df,v4df) +v8sf __builtin_ia32_hsubps256 (v8sf,v8sf) +v32qi __builtin_ia32_lddqu256 (pcchar) +v32qi __builtin_ia32_loaddqu256 (pcchar) +v4df __builtin_ia32_loadupd256 (pcdouble) +v8sf __builtin_ia32_loadups256 (pcfloat) +v2df __builtin_ia32_maskloadpd (pcv2df,v2df) +v4df __builtin_ia32_maskloadpd256 (pcv4df,v4df) +v4sf __builtin_ia32_maskloadps (pcv4sf,v4sf) +v8sf __builtin_ia32_maskloadps256 (pcv8sf,v8sf) +void __builtin_ia32_maskstorepd (pv2df,v2df,v2df) +void __builtin_ia32_maskstorepd256 (pv4df,v4df,v4df) +void __builtin_ia32_maskstoreps (pv4sf,v4sf,v4sf) +void __builtin_ia32_maskstoreps256 (pv8sf,v8sf,v8sf) +v4df __builtin_ia32_maxpd256 (v4df,v4df) +v8sf __builtin_ia32_maxps256 (v8sf,v8sf) +v4df __builtin_ia32_minpd256 (v4df,v4df) +v8sf __builtin_ia32_minps256 (v8sf,v8sf) +v4df __builtin_ia32_movddup256 (v4df) +int __builtin_ia32_movmskpd256 (v4df) +int __builtin_ia32_movmskps256 (v8sf) +v8sf __builtin_ia32_movshdup256 (v8sf) +v8sf __builtin_ia32_movsldup256 (v8sf) +v4df __builtin_ia32_mulpd256 (v4df,v4df) +v8sf __builtin_ia32_mulps256 (v8sf,v8sf) +v4df __builtin_ia32_orpd256 (v4df,v4df) +v8sf __builtin_ia32_orps256 (v8sf,v8sf) +v2df __builtin_ia32_pd_pd256 (v4df) +v4df __builtin_ia32_pd256_pd (v2df) +v4sf __builtin_ia32_ps_ps256 (v8sf) +v8sf __builtin_ia32_ps256_ps (v4sf) +int __builtin_ia32_ptestc256 (v4di,v4di,ptest) +int __builtin_ia32_ptestnzc256 (v4di,v4di,ptest) +int __builtin_ia32_ptestz256 (v4di,v4di,ptest) +v8sf __builtin_ia32_rcpps256 (v8sf) +v4df __builtin_ia32_roundpd256 (v4df,int) +v8sf __builtin_ia32_roundps256 (v8sf,int) +v8sf __builtin_ia32_rsqrtps_nr256 (v8sf) +v8sf __builtin_ia32_rsqrtps256 (v8sf) +v4df __builtin_ia32_shufpd256 (v4df,v4df,int) +v8sf __builtin_ia32_shufps256 (v8sf,v8sf,int) +v4si __builtin_ia32_si_si256 (v8si) +v8si __builtin_ia32_si256_si (v4si) +v4df __builtin_ia32_sqrtpd256 (v4df) +v8sf __builtin_ia32_sqrtps_nr256 (v8sf) +v8sf __builtin_ia32_sqrtps256 (v8sf) +void __builtin_ia32_storedqu256 (pchar,v32qi) +void __builtin_ia32_storeupd256 (pdouble,v4df) +void __builtin_ia32_storeups256 (pfloat,v8sf) +v4df __builtin_ia32_subpd256 (v4df,v4df) +v8sf __builtin_ia32_subps256 (v8sf,v8sf) +v4df __builtin_ia32_unpckhpd256 (v4df,v4df) +v8sf __builtin_ia32_unpckhps256 (v8sf,v8sf) +v4df __builtin_ia32_unpcklpd256 (v4df,v4df) +v8sf __builtin_ia32_unpcklps256 (v8sf,v8sf) +v4df __builtin_ia32_vbroadcastf128_pd256 (pcv2df) +v8sf __builtin_ia32_vbroadcastf128_ps256 (pcv4sf) +v4df __builtin_ia32_vbroadcastsd256 (pcdouble) +v4sf __builtin_ia32_vbroadcastss (pcfloat) +v8sf __builtin_ia32_vbroadcastss256 (pcfloat) +v2df __builtin_ia32_vextractf128_pd256 (v4df,int) +v4sf __builtin_ia32_vextractf128_ps256 (v8sf,int) +v4si __builtin_ia32_vextractf128_si256 (v8si,int) +v4df __builtin_ia32_vinsertf128_pd256 (v4df,v2df,int) +v8sf __builtin_ia32_vinsertf128_ps256 (v8sf,v4sf,int) +v8si __builtin_ia32_vinsertf128_si256 (v8si,v4si,int) +v4df __builtin_ia32_vperm2f128_pd256 (v4df,v4df,int) +v8sf __builtin_ia32_vperm2f128_ps256 (v8sf,v8sf,int) +v8si __builtin_ia32_vperm2f128_si256 (v8si,v8si,int) +v2df __builtin_ia32_vpermil2pd (v2df,v2df,v2di,int) +v4df __builtin_ia32_vpermil2pd256 (v4df,v4df,v4di,int) +v4sf __builtin_ia32_vpermil2ps (v4sf,v4sf,v4si,int) +v8sf __builtin_ia32_vpermil2ps256 (v8sf,v8sf,v8si,int) +v2df __builtin_ia32_vpermilpd (v2df,int) +v4df __builtin_ia32_vpermilpd256 (v4df,int) +v4sf __builtin_ia32_vpermilps (v4sf,int) +v8sf __builtin_ia32_vpermilps256 (v8sf,int) +v2df __builtin_ia32_vpermilvarpd (v2df,v2di) +v4df __builtin_ia32_vpermilvarpd256 (v4df,v4di) +v4sf __builtin_ia32_vpermilvarps (v4sf,v4si) +v8sf __builtin_ia32_vpermilvarps256 (v8sf,v8si) +int __builtin_ia32_vtestcpd (v2df,v2df,ptest) +int __builtin_ia32_vtestcpd256 (v4df,v4df,ptest) +int __builtin_ia32_vtestcps (v4sf,v4sf,ptest) +int __builtin_ia32_vtestcps256 (v8sf,v8sf,ptest) +int __builtin_ia32_vtestnzcpd (v2df,v2df,ptest) +int __builtin_ia32_vtestnzcpd256 (v4df,v4df,ptest) +int __builtin_ia32_vtestnzcps (v4sf,v4sf,ptest) +int __builtin_ia32_vtestnzcps256 (v8sf,v8sf,ptest) +int __builtin_ia32_vtestzpd (v2df,v2df,ptest) +int __builtin_ia32_vtestzpd256 (v4df,v4df,ptest) +int __builtin_ia32_vtestzps (v4sf,v4sf,ptest) +int __builtin_ia32_vtestzps256 (v8sf,v8sf,ptest) +void __builtin_ia32_vzeroall (void) +void __builtin_ia32_vzeroupper (void) +v4df __builtin_ia32_xorpd256 (v4df,v4df) +v8sf __builtin_ia32_xorps256 (v8sf,v8sf) +@end smallexample + +The following built-in functions are available when @option{-maes} is +used. All of them generate the machine instruction that is part of the +name. + +@smallexample +v2di __builtin_ia32_aesenc128 (v2di, v2di) +v2di __builtin_ia32_aesenclast128 (v2di, v2di) +v2di __builtin_ia32_aesdec128 (v2di, v2di) +v2di __builtin_ia32_aesdeclast128 (v2di, v2di) +v2di __builtin_ia32_aeskeygenassist128 (v2di, const int) +v2di __builtin_ia32_aesimc128 (v2di) +@end smallexample + +The following built-in function is available when @option{-mpclmul} is +used. + +@table @code +@item v2di __builtin_ia32_pclmulqdq128 (v2di, v2di, const int) +Generates the @code{pclmulqdq} machine instruction. +@end table + +The following built-in function is available when @option{-mfsgsbase} is +used. All of them generate the machine instruction that is part of the +name. + +@smallexample +unsigned int __builtin_ia32_rdfsbase32 (void) +unsigned long long __builtin_ia32_rdfsbase64 (void) +unsigned int __builtin_ia32_rdgsbase32 (void) +unsigned long long __builtin_ia32_rdgsbase64 (void) +void _writefsbase_u32 (unsigned int) +void _writefsbase_u64 (unsigned long long) +void _writegsbase_u32 (unsigned int) +void _writegsbase_u64 (unsigned long long) +@end smallexample + +The following built-in function is available when @option{-mrdrnd} is +used. All of them generate the machine instruction that is part of the +name. + +@smallexample +unsigned int __builtin_ia32_rdrand16_step (unsigned short *) +unsigned int __builtin_ia32_rdrand32_step (unsigned int *) +unsigned int __builtin_ia32_rdrand64_step (unsigned long long *) +@end smallexample + +The following built-in functions are available when @option{-msse4a} is used. +All of them generate the machine instruction that is part of the name. + +@smallexample +void __builtin_ia32_movntsd (double *, v2df) +void __builtin_ia32_movntss (float *, v4sf) +v2di __builtin_ia32_extrq (v2di, v16qi) +v2di __builtin_ia32_extrqi (v2di, const unsigned int, const unsigned int) +v2di __builtin_ia32_insertq (v2di, v2di) +v2di __builtin_ia32_insertqi (v2di, v2di, const unsigned int, const unsigned int) +@end smallexample + +The following built-in functions are available when @option{-mxop} is used. +@smallexample +v2df __builtin_ia32_vfrczpd (v2df) +v4sf __builtin_ia32_vfrczps (v4sf) +v2df __builtin_ia32_vfrczsd (v2df, v2df) +v4sf __builtin_ia32_vfrczss (v4sf, v4sf) +v4df __builtin_ia32_vfrczpd256 (v4df) +v8sf __builtin_ia32_vfrczps256 (v8sf) +v2di __builtin_ia32_vpcmov (v2di, v2di, v2di) +v2di __builtin_ia32_vpcmov_v2di (v2di, v2di, v2di) +v4si __builtin_ia32_vpcmov_v4si (v4si, v4si, v4si) +v8hi __builtin_ia32_vpcmov_v8hi (v8hi, v8hi, v8hi) +v16qi __builtin_ia32_vpcmov_v16qi (v16qi, v16qi, v16qi) +v2df __builtin_ia32_vpcmov_v2df (v2df, v2df, v2df) +v4sf __builtin_ia32_vpcmov_v4sf (v4sf, v4sf, v4sf) +v4di __builtin_ia32_vpcmov_v4di256 (v4di, v4di, v4di) +v8si __builtin_ia32_vpcmov_v8si256 (v8si, v8si, v8si) +v16hi __builtin_ia32_vpcmov_v16hi256 (v16hi, v16hi, v16hi) +v32qi __builtin_ia32_vpcmov_v32qi256 (v32qi, v32qi, v32qi) +v4df __builtin_ia32_vpcmov_v4df256 (v4df, v4df, v4df) +v8sf __builtin_ia32_vpcmov_v8sf256 (v8sf, v8sf, v8sf) +v16qi __builtin_ia32_vpcomeqb (v16qi, v16qi) +v8hi __builtin_ia32_vpcomeqw (v8hi, v8hi) +v4si __builtin_ia32_vpcomeqd (v4si, v4si) +v2di __builtin_ia32_vpcomeqq (v2di, v2di) +v16qi __builtin_ia32_vpcomequb (v16qi, v16qi) +v4si __builtin_ia32_vpcomequd (v4si, v4si) +v2di __builtin_ia32_vpcomequq (v2di, v2di) +v8hi __builtin_ia32_vpcomequw (v8hi, v8hi) +v8hi __builtin_ia32_vpcomeqw (v8hi, v8hi) +v16qi __builtin_ia32_vpcomfalseb (v16qi, v16qi) +v4si __builtin_ia32_vpcomfalsed (v4si, v4si) +v2di __builtin_ia32_vpcomfalseq (v2di, v2di) +v16qi __builtin_ia32_vpcomfalseub (v16qi, v16qi) +v4si __builtin_ia32_vpcomfalseud (v4si, v4si) +v2di __builtin_ia32_vpcomfalseuq (v2di, v2di) +v8hi __builtin_ia32_vpcomfalseuw (v8hi, v8hi) +v8hi __builtin_ia32_vpcomfalsew (v8hi, v8hi) +v16qi __builtin_ia32_vpcomgeb (v16qi, v16qi) +v4si __builtin_ia32_vpcomged (v4si, v4si) +v2di __builtin_ia32_vpcomgeq (v2di, v2di) +v16qi __builtin_ia32_vpcomgeub (v16qi, v16qi) +v4si __builtin_ia32_vpcomgeud (v4si, v4si) +v2di __builtin_ia32_vpcomgeuq (v2di, v2di) +v8hi __builtin_ia32_vpcomgeuw (v8hi, v8hi) +v8hi __builtin_ia32_vpcomgew (v8hi, v8hi) +v16qi __builtin_ia32_vpcomgtb (v16qi, v16qi) +v4si __builtin_ia32_vpcomgtd (v4si, v4si) +v2di __builtin_ia32_vpcomgtq (v2di, v2di) +v16qi __builtin_ia32_vpcomgtub (v16qi, v16qi) +v4si __builtin_ia32_vpcomgtud (v4si, v4si) +v2di __builtin_ia32_vpcomgtuq (v2di, v2di) +v8hi __builtin_ia32_vpcomgtuw (v8hi, v8hi) +v8hi __builtin_ia32_vpcomgtw (v8hi, v8hi) +v16qi __builtin_ia32_vpcomleb (v16qi, v16qi) +v4si __builtin_ia32_vpcomled (v4si, v4si) +v2di __builtin_ia32_vpcomleq (v2di, v2di) +v16qi __builtin_ia32_vpcomleub (v16qi, v16qi) +v4si __builtin_ia32_vpcomleud (v4si, v4si) +v2di __builtin_ia32_vpcomleuq (v2di, v2di) +v8hi __builtin_ia32_vpcomleuw (v8hi, v8hi) +v8hi __builtin_ia32_vpcomlew (v8hi, v8hi) +v16qi __builtin_ia32_vpcomltb (v16qi, v16qi) +v4si __builtin_ia32_vpcomltd (v4si, v4si) +v2di __builtin_ia32_vpcomltq (v2di, v2di) +v16qi __builtin_ia32_vpcomltub (v16qi, v16qi) +v4si __builtin_ia32_vpcomltud (v4si, v4si) +v2di __builtin_ia32_vpcomltuq (v2di, v2di) +v8hi __builtin_ia32_vpcomltuw (v8hi, v8hi) +v8hi __builtin_ia32_vpcomltw (v8hi, v8hi) +v16qi __builtin_ia32_vpcomneb (v16qi, v16qi) +v4si __builtin_ia32_vpcomned (v4si, v4si) +v2di __builtin_ia32_vpcomneq (v2di, v2di) +v16qi __builtin_ia32_vpcomneub (v16qi, v16qi) +v4si __builtin_ia32_vpcomneud (v4si, v4si) +v2di __builtin_ia32_vpcomneuq (v2di, v2di) +v8hi __builtin_ia32_vpcomneuw (v8hi, v8hi) +v8hi __builtin_ia32_vpcomnew (v8hi, v8hi) +v16qi __builtin_ia32_vpcomtrueb (v16qi, v16qi) +v4si __builtin_ia32_vpcomtrued (v4si, v4si) +v2di __builtin_ia32_vpcomtrueq (v2di, v2di) +v16qi __builtin_ia32_vpcomtrueub (v16qi, v16qi) +v4si __builtin_ia32_vpcomtrueud (v4si, v4si) +v2di __builtin_ia32_vpcomtrueuq (v2di, v2di) +v8hi __builtin_ia32_vpcomtrueuw (v8hi, v8hi) +v8hi __builtin_ia32_vpcomtruew (v8hi, v8hi) +v4si __builtin_ia32_vphaddbd (v16qi) +v2di __builtin_ia32_vphaddbq (v16qi) +v8hi __builtin_ia32_vphaddbw (v16qi) +v2di __builtin_ia32_vphadddq (v4si) +v4si __builtin_ia32_vphaddubd (v16qi) +v2di __builtin_ia32_vphaddubq (v16qi) +v8hi __builtin_ia32_vphaddubw (v16qi) +v2di __builtin_ia32_vphaddudq (v4si) +v4si __builtin_ia32_vphadduwd (v8hi) +v2di __builtin_ia32_vphadduwq (v8hi) +v4si __builtin_ia32_vphaddwd (v8hi) +v2di __builtin_ia32_vphaddwq (v8hi) +v8hi __builtin_ia32_vphsubbw (v16qi) +v2di __builtin_ia32_vphsubdq (v4si) +v4si __builtin_ia32_vphsubwd (v8hi) +v4si __builtin_ia32_vpmacsdd (v4si, v4si, v4si) +v2di __builtin_ia32_vpmacsdqh (v4si, v4si, v2di) +v2di __builtin_ia32_vpmacsdql (v4si, v4si, v2di) +v4si __builtin_ia32_vpmacssdd (v4si, v4si, v4si) +v2di __builtin_ia32_vpmacssdqh (v4si, v4si, v2di) +v2di __builtin_ia32_vpmacssdql (v4si, v4si, v2di) +v4si __builtin_ia32_vpmacsswd (v8hi, v8hi, v4si) +v8hi __builtin_ia32_vpmacssww (v8hi, v8hi, v8hi) +v4si __builtin_ia32_vpmacswd (v8hi, v8hi, v4si) +v8hi __builtin_ia32_vpmacsww (v8hi, v8hi, v8hi) +v4si __builtin_ia32_vpmadcsswd (v8hi, v8hi, v4si) +v4si __builtin_ia32_vpmadcswd (v8hi, v8hi, v4si) +v16qi __builtin_ia32_vpperm (v16qi, v16qi, v16qi) +v16qi __builtin_ia32_vprotb (v16qi, v16qi) +v4si __builtin_ia32_vprotd (v4si, v4si) +v2di __builtin_ia32_vprotq (v2di, v2di) +v8hi __builtin_ia32_vprotw (v8hi, v8hi) +v16qi __builtin_ia32_vpshab (v16qi, v16qi) +v4si __builtin_ia32_vpshad (v4si, v4si) +v2di __builtin_ia32_vpshaq (v2di, v2di) +v8hi __builtin_ia32_vpshaw (v8hi, v8hi) +v16qi __builtin_ia32_vpshlb (v16qi, v16qi) +v4si __builtin_ia32_vpshld (v4si, v4si) +v2di __builtin_ia32_vpshlq (v2di, v2di) +v8hi __builtin_ia32_vpshlw (v8hi, v8hi) +@end smallexample + +The following built-in functions are available when @option{-mfma4} is used. +All of them generate the machine instruction that is part of the name +with MMX registers. + +@smallexample +v2df __builtin_ia32_fmaddpd (v2df, v2df, v2df) +v4sf __builtin_ia32_fmaddps (v4sf, v4sf, v4sf) +v2df __builtin_ia32_fmaddsd (v2df, v2df, v2df) +v4sf __builtin_ia32_fmaddss (v4sf, v4sf, v4sf) +v2df __builtin_ia32_fmsubpd (v2df, v2df, v2df) +v4sf __builtin_ia32_fmsubps (v4sf, v4sf, v4sf) +v2df __builtin_ia32_fmsubsd (v2df, v2df, v2df) +v4sf __builtin_ia32_fmsubss (v4sf, v4sf, v4sf) +v2df __builtin_ia32_fnmaddpd (v2df, v2df, v2df) +v4sf __builtin_ia32_fnmaddps (v4sf, v4sf, v4sf) +v2df __builtin_ia32_fnmaddsd (v2df, v2df, v2df) +v4sf __builtin_ia32_fnmaddss (v4sf, v4sf, v4sf) +v2df __builtin_ia32_fnmsubpd (v2df, v2df, v2df) +v4sf __builtin_ia32_fnmsubps (v4sf, v4sf, v4sf) +v2df __builtin_ia32_fnmsubsd (v2df, v2df, v2df) +v4sf __builtin_ia32_fnmsubss (v4sf, v4sf, v4sf) +v2df __builtin_ia32_fmaddsubpd (v2df, v2df, v2df) +v4sf __builtin_ia32_fmaddsubps (v4sf, v4sf, v4sf) +v2df __builtin_ia32_fmsubaddpd (v2df, v2df, v2df) +v4sf __builtin_ia32_fmsubaddps (v4sf, v4sf, v4sf) +v4df __builtin_ia32_fmaddpd256 (v4df, v4df, v4df) +v8sf __builtin_ia32_fmaddps256 (v8sf, v8sf, v8sf) +v4df __builtin_ia32_fmsubpd256 (v4df, v4df, v4df) +v8sf __builtin_ia32_fmsubps256 (v8sf, v8sf, v8sf) +v4df __builtin_ia32_fnmaddpd256 (v4df, v4df, v4df) +v8sf __builtin_ia32_fnmaddps256 (v8sf, v8sf, v8sf) +v4df __builtin_ia32_fnmsubpd256 (v4df, v4df, v4df) +v8sf __builtin_ia32_fnmsubps256 (v8sf, v8sf, v8sf) +v4df __builtin_ia32_fmaddsubpd256 (v4df, v4df, v4df) +v8sf __builtin_ia32_fmaddsubps256 (v8sf, v8sf, v8sf) +v4df __builtin_ia32_fmsubaddpd256 (v4df, v4df, v4df) +v8sf __builtin_ia32_fmsubaddps256 (v8sf, v8sf, v8sf) + +@end smallexample + +The following built-in functions are available when @option{-mlwp} is used. + +@smallexample +void __builtin_ia32_llwpcb16 (void *); +void __builtin_ia32_llwpcb32 (void *); +void __builtin_ia32_llwpcb64 (void *); +void * __builtin_ia32_llwpcb16 (void); +void * __builtin_ia32_llwpcb32 (void); +void * __builtin_ia32_llwpcb64 (void); +void __builtin_ia32_lwpval16 (unsigned short, unsigned int, unsigned short) +void __builtin_ia32_lwpval32 (unsigned int, unsigned int, unsigned int) +void __builtin_ia32_lwpval64 (unsigned __int64, unsigned int, unsigned int) +unsigned char __builtin_ia32_lwpins16 (unsigned short, unsigned int, unsigned short) +unsigned char __builtin_ia32_lwpins32 (unsigned int, unsigned int, unsigned int) +unsigned char __builtin_ia32_lwpins64 (unsigned __int64, unsigned int, unsigned int) +@end smallexample + +The following built-in functions are available when @option{-mbmi} is used. +All of them generate the machine instruction that is part of the name. +@smallexample +unsigned int __builtin_ia32_bextr_u32(unsigned int, unsigned int); +unsigned long long __builtin_ia32_bextr_u64 (unsigned long long, unsigned long long); +unsigned short __builtin_ia32_lzcnt_16(unsigned short); +unsigned int __builtin_ia32_lzcnt_u32(unsigned int); +unsigned long long __builtin_ia32_lzcnt_u64 (unsigned long long); +@end smallexample + +The following built-in functions are available when @option{-mtbm} is used. +Both of them generate the immediate form of the bextr machine instruction. +@smallexample +unsigned int __builtin_ia32_bextri_u32 (unsigned int, const unsigned int); +unsigned long long __builtin_ia32_bextri_u64 (unsigned long long, const unsigned long long); +@end smallexample + + +The following built-in functions are available when @option{-m3dnow} is used. +All of them generate the machine instruction that is part of the name. + +@smallexample +void __builtin_ia32_femms (void) +v8qi __builtin_ia32_pavgusb (v8qi, v8qi) +v2si __builtin_ia32_pf2id (v2sf) +v2sf __builtin_ia32_pfacc (v2sf, v2sf) +v2sf __builtin_ia32_pfadd (v2sf, v2sf) +v2si __builtin_ia32_pfcmpeq (v2sf, v2sf) +v2si __builtin_ia32_pfcmpge (v2sf, v2sf) +v2si __builtin_ia32_pfcmpgt (v2sf, v2sf) +v2sf __builtin_ia32_pfmax (v2sf, v2sf) +v2sf __builtin_ia32_pfmin (v2sf, v2sf) +v2sf __builtin_ia32_pfmul (v2sf, v2sf) +v2sf __builtin_ia32_pfrcp (v2sf) +v2sf __builtin_ia32_pfrcpit1 (v2sf, v2sf) +v2sf __builtin_ia32_pfrcpit2 (v2sf, v2sf) +v2sf __builtin_ia32_pfrsqrt (v2sf) +v2sf __builtin_ia32_pfrsqrtit1 (v2sf, v2sf) +v2sf __builtin_ia32_pfsub (v2sf, v2sf) +v2sf __builtin_ia32_pfsubr (v2sf, v2sf) +v2sf __builtin_ia32_pi2fd (v2si) +v4hi __builtin_ia32_pmulhrw (v4hi, v4hi) +@end smallexample + +The following built-in functions are available when both @option{-m3dnow} +and @option{-march=athlon} are used. All of them generate the machine +instruction that is part of the name. + +@smallexample +v2si __builtin_ia32_pf2iw (v2sf) +v2sf __builtin_ia32_pfnacc (v2sf, v2sf) +v2sf __builtin_ia32_pfpnacc (v2sf, v2sf) +v2sf __builtin_ia32_pi2fw (v2si) +v2sf __builtin_ia32_pswapdsf (v2sf) +v2si __builtin_ia32_pswapdsi (v2si) +@end smallexample + +@node MIPS DSP Built-in Functions +@subsection MIPS DSP Built-in Functions + +The MIPS DSP Application-Specific Extension (ASE) includes new +instructions that are designed to improve the performance of DSP and +media applications. It provides instructions that operate on packed +8-bit/16-bit integer data, Q7, Q15 and Q31 fractional data. + +GCC supports MIPS DSP operations using both the generic +vector extensions (@pxref{Vector Extensions}) and a collection of +MIPS-specific built-in functions. Both kinds of support are +enabled by the @option{-mdsp} command-line option. + +Revision 2 of the ASE was introduced in the second half of 2006. +This revision adds extra instructions to the original ASE, but is +otherwise backwards-compatible with it. You can select revision 2 +using the command-line option @option{-mdspr2}; this option implies +@option{-mdsp}. + +The SCOUNT and POS bits of the DSP control register are global. The +WRDSP, EXTPDP, EXTPDPV and MTHLIP instructions modify the SCOUNT and +POS bits. During optimization, the compiler will not delete these +instructions and it will not delete calls to functions containing +these instructions. + +At present, GCC only provides support for operations on 32-bit +vectors. The vector type associated with 8-bit integer data is +usually called @code{v4i8}, the vector type associated with Q7 +is usually called @code{v4q7}, the vector type associated with 16-bit +integer data is usually called @code{v2i16}, and the vector type +associated with Q15 is usually called @code{v2q15}. They can be +defined in C as follows: + +@smallexample +typedef signed char v4i8 __attribute__ ((vector_size(4))); +typedef signed char v4q7 __attribute__ ((vector_size(4))); +typedef short v2i16 __attribute__ ((vector_size(4))); +typedef short v2q15 __attribute__ ((vector_size(4))); +@end smallexample + +@code{v4i8}, @code{v4q7}, @code{v2i16} and @code{v2q15} values are +initialized in the same way as aggregates. For example: + +@smallexample +v4i8 a = @{1, 2, 3, 4@}; +v4i8 b; +b = (v4i8) @{5, 6, 7, 8@}; + +v2q15 c = @{0x0fcb, 0x3a75@}; +v2q15 d; +d = (v2q15) @{0.1234 * 0x1.0p15, 0.4567 * 0x1.0p15@}; +@end smallexample + +@emph{Note:} The CPU's endianness determines the order in which values +are packed. On little-endian targets, the first value is the least +significant and the last value is the most significant. The opposite +order applies to big-endian targets. For example, the code above will +set the lowest byte of @code{a} to @code{1} on little-endian targets +and @code{4} on big-endian targets. + +@emph{Note:} Q7, Q15 and Q31 values must be initialized with their integer +representation. As shown in this example, the integer representation +of a Q7 value can be obtained by multiplying the fractional value by +@code{0x1.0p7}. The equivalent for Q15 values is to multiply by +@code{0x1.0p15}. The equivalent for Q31 values is to multiply by +@code{0x1.0p31}. + +The table below lists the @code{v4i8} and @code{v2q15} operations for which +hardware support exists. @code{a} and @code{b} are @code{v4i8} values, +and @code{c} and @code{d} are @code{v2q15} values. + +@multitable @columnfractions .50 .50 +@item C code @tab MIPS instruction +@item @code{a + b} @tab @code{addu.qb} +@item @code{c + d} @tab @code{addq.ph} +@item @code{a - b} @tab @code{subu.qb} +@item @code{c - d} @tab @code{subq.ph} +@end multitable + +The table below lists the @code{v2i16} operation for which +hardware support exists for the DSP ASE REV 2. @code{e} and @code{f} are +@code{v2i16} values. + +@multitable @columnfractions .50 .50 +@item C code @tab MIPS instruction +@item @code{e * f} @tab @code{mul.ph} +@end multitable + +It is easier to describe the DSP built-in functions if we first define +the following types: + +@smallexample +typedef int q31; +typedef int i32; +typedef unsigned int ui32; +typedef long long a64; +@end smallexample + +@code{q31} and @code{i32} are actually the same as @code{int}, but we +use @code{q31} to indicate a Q31 fractional value and @code{i32} to +indicate a 32-bit integer value. Similarly, @code{a64} is the same as +@code{long long}, but we use @code{a64} to indicate values that will +be placed in one of the four DSP accumulators (@code{$ac0}, +@code{$ac1}, @code{$ac2} or @code{$ac3}). + +Also, some built-in functions prefer or require immediate numbers as +parameters, because the corresponding DSP instructions accept both immediate +numbers and register operands, or accept immediate numbers only. The +immediate parameters are listed as follows. + +@smallexample +imm0_3: 0 to 3. +imm0_7: 0 to 7. +imm0_15: 0 to 15. +imm0_31: 0 to 31. +imm0_63: 0 to 63. +imm0_255: 0 to 255. +imm_n32_31: -32 to 31. +imm_n512_511: -512 to 511. +@end smallexample + +The following built-in functions map directly to a particular MIPS DSP +instruction. Please refer to the architecture specification +for details on what each instruction does. + +@smallexample +v2q15 __builtin_mips_addq_ph (v2q15, v2q15) +v2q15 __builtin_mips_addq_s_ph (v2q15, v2q15) +q31 __builtin_mips_addq_s_w (q31, q31) +v4i8 __builtin_mips_addu_qb (v4i8, v4i8) +v4i8 __builtin_mips_addu_s_qb (v4i8, v4i8) +v2q15 __builtin_mips_subq_ph (v2q15, v2q15) +v2q15 __builtin_mips_subq_s_ph (v2q15, v2q15) +q31 __builtin_mips_subq_s_w (q31, q31) +v4i8 __builtin_mips_subu_qb (v4i8, v4i8) +v4i8 __builtin_mips_subu_s_qb (v4i8, v4i8) +i32 __builtin_mips_addsc (i32, i32) +i32 __builtin_mips_addwc (i32, i32) +i32 __builtin_mips_modsub (i32, i32) +i32 __builtin_mips_raddu_w_qb (v4i8) +v2q15 __builtin_mips_absq_s_ph (v2q15) +q31 __builtin_mips_absq_s_w (q31) +v4i8 __builtin_mips_precrq_qb_ph (v2q15, v2q15) +v2q15 __builtin_mips_precrq_ph_w (q31, q31) +v2q15 __builtin_mips_precrq_rs_ph_w (q31, q31) +v4i8 __builtin_mips_precrqu_s_qb_ph (v2q15, v2q15) +q31 __builtin_mips_preceq_w_phl (v2q15) +q31 __builtin_mips_preceq_w_phr (v2q15) +v2q15 __builtin_mips_precequ_ph_qbl (v4i8) +v2q15 __builtin_mips_precequ_ph_qbr (v4i8) +v2q15 __builtin_mips_precequ_ph_qbla (v4i8) +v2q15 __builtin_mips_precequ_ph_qbra (v4i8) +v2q15 __builtin_mips_preceu_ph_qbl (v4i8) +v2q15 __builtin_mips_preceu_ph_qbr (v4i8) +v2q15 __builtin_mips_preceu_ph_qbla (v4i8) +v2q15 __builtin_mips_preceu_ph_qbra (v4i8) +v4i8 __builtin_mips_shll_qb (v4i8, imm0_7) +v4i8 __builtin_mips_shll_qb (v4i8, i32) +v2q15 __builtin_mips_shll_ph (v2q15, imm0_15) +v2q15 __builtin_mips_shll_ph (v2q15, i32) +v2q15 __builtin_mips_shll_s_ph (v2q15, imm0_15) +v2q15 __builtin_mips_shll_s_ph (v2q15, i32) +q31 __builtin_mips_shll_s_w (q31, imm0_31) +q31 __builtin_mips_shll_s_w (q31, i32) +v4i8 __builtin_mips_shrl_qb (v4i8, imm0_7) +v4i8 __builtin_mips_shrl_qb (v4i8, i32) +v2q15 __builtin_mips_shra_ph (v2q15, imm0_15) +v2q15 __builtin_mips_shra_ph (v2q15, i32) +v2q15 __builtin_mips_shra_r_ph (v2q15, imm0_15) +v2q15 __builtin_mips_shra_r_ph (v2q15, i32) +q31 __builtin_mips_shra_r_w (q31, imm0_31) +q31 __builtin_mips_shra_r_w (q31, i32) +v2q15 __builtin_mips_muleu_s_ph_qbl (v4i8, v2q15) +v2q15 __builtin_mips_muleu_s_ph_qbr (v4i8, v2q15) +v2q15 __builtin_mips_mulq_rs_ph (v2q15, v2q15) +q31 __builtin_mips_muleq_s_w_phl (v2q15, v2q15) +q31 __builtin_mips_muleq_s_w_phr (v2q15, v2q15) +a64 __builtin_mips_dpau_h_qbl (a64, v4i8, v4i8) +a64 __builtin_mips_dpau_h_qbr (a64, v4i8, v4i8) +a64 __builtin_mips_dpsu_h_qbl (a64, v4i8, v4i8) +a64 __builtin_mips_dpsu_h_qbr (a64, v4i8, v4i8) +a64 __builtin_mips_dpaq_s_w_ph (a64, v2q15, v2q15) +a64 __builtin_mips_dpaq_sa_l_w (a64, q31, q31) +a64 __builtin_mips_dpsq_s_w_ph (a64, v2q15, v2q15) +a64 __builtin_mips_dpsq_sa_l_w (a64, q31, q31) +a64 __builtin_mips_mulsaq_s_w_ph (a64, v2q15, v2q15) +a64 __builtin_mips_maq_s_w_phl (a64, v2q15, v2q15) +a64 __builtin_mips_maq_s_w_phr (a64, v2q15, v2q15) +a64 __builtin_mips_maq_sa_w_phl (a64, v2q15, v2q15) +a64 __builtin_mips_maq_sa_w_phr (a64, v2q15, v2q15) +i32 __builtin_mips_bitrev (i32) +i32 __builtin_mips_insv (i32, i32) +v4i8 __builtin_mips_repl_qb (imm0_255) +v4i8 __builtin_mips_repl_qb (i32) +v2q15 __builtin_mips_repl_ph (imm_n512_511) +v2q15 __builtin_mips_repl_ph (i32) +void __builtin_mips_cmpu_eq_qb (v4i8, v4i8) +void __builtin_mips_cmpu_lt_qb (v4i8, v4i8) +void __builtin_mips_cmpu_le_qb (v4i8, v4i8) +i32 __builtin_mips_cmpgu_eq_qb (v4i8, v4i8) +i32 __builtin_mips_cmpgu_lt_qb (v4i8, v4i8) +i32 __builtin_mips_cmpgu_le_qb (v4i8, v4i8) +void __builtin_mips_cmp_eq_ph (v2q15, v2q15) +void __builtin_mips_cmp_lt_ph (v2q15, v2q15) +void __builtin_mips_cmp_le_ph (v2q15, v2q15) +v4i8 __builtin_mips_pick_qb (v4i8, v4i8) +v2q15 __builtin_mips_pick_ph (v2q15, v2q15) +v2q15 __builtin_mips_packrl_ph (v2q15, v2q15) +i32 __builtin_mips_extr_w (a64, imm0_31) +i32 __builtin_mips_extr_w (a64, i32) +i32 __builtin_mips_extr_r_w (a64, imm0_31) +i32 __builtin_mips_extr_s_h (a64, i32) +i32 __builtin_mips_extr_rs_w (a64, imm0_31) +i32 __builtin_mips_extr_rs_w (a64, i32) +i32 __builtin_mips_extr_s_h (a64, imm0_31) +i32 __builtin_mips_extr_r_w (a64, i32) +i32 __builtin_mips_extp (a64, imm0_31) +i32 __builtin_mips_extp (a64, i32) +i32 __builtin_mips_extpdp (a64, imm0_31) +i32 __builtin_mips_extpdp (a64, i32) +a64 __builtin_mips_shilo (a64, imm_n32_31) +a64 __builtin_mips_shilo (a64, i32) +a64 __builtin_mips_mthlip (a64, i32) +void __builtin_mips_wrdsp (i32, imm0_63) +i32 __builtin_mips_rddsp (imm0_63) +i32 __builtin_mips_lbux (void *, i32) +i32 __builtin_mips_lhx (void *, i32) +i32 __builtin_mips_lwx (void *, i32) +i32 __builtin_mips_bposge32 (void) +a64 __builtin_mips_madd (a64, i32, i32); +a64 __builtin_mips_maddu (a64, ui32, ui32); +a64 __builtin_mips_msub (a64, i32, i32); +a64 __builtin_mips_msubu (a64, ui32, ui32); +a64 __builtin_mips_mult (i32, i32); +a64 __builtin_mips_multu (ui32, ui32); +@end smallexample + +The following built-in functions map directly to a particular MIPS DSP REV 2 +instruction. Please refer to the architecture specification +for details on what each instruction does. + +@smallexample +v4q7 __builtin_mips_absq_s_qb (v4q7); +v2i16 __builtin_mips_addu_ph (v2i16, v2i16); +v2i16 __builtin_mips_addu_s_ph (v2i16, v2i16); +v4i8 __builtin_mips_adduh_qb (v4i8, v4i8); +v4i8 __builtin_mips_adduh_r_qb (v4i8, v4i8); +i32 __builtin_mips_append (i32, i32, imm0_31); +i32 __builtin_mips_balign (i32, i32, imm0_3); +i32 __builtin_mips_cmpgdu_eq_qb (v4i8, v4i8); +i32 __builtin_mips_cmpgdu_lt_qb (v4i8, v4i8); +i32 __builtin_mips_cmpgdu_le_qb (v4i8, v4i8); +a64 __builtin_mips_dpa_w_ph (a64, v2i16, v2i16); +a64 __builtin_mips_dps_w_ph (a64, v2i16, v2i16); +v2i16 __builtin_mips_mul_ph (v2i16, v2i16); +v2i16 __builtin_mips_mul_s_ph (v2i16, v2i16); +q31 __builtin_mips_mulq_rs_w (q31, q31); +v2q15 __builtin_mips_mulq_s_ph (v2q15, v2q15); +q31 __builtin_mips_mulq_s_w (q31, q31); +a64 __builtin_mips_mulsa_w_ph (a64, v2i16, v2i16); +v4i8 __builtin_mips_precr_qb_ph (v2i16, v2i16); +v2i16 __builtin_mips_precr_sra_ph_w (i32, i32, imm0_31); +v2i16 __builtin_mips_precr_sra_r_ph_w (i32, i32, imm0_31); +i32 __builtin_mips_prepend (i32, i32, imm0_31); +v4i8 __builtin_mips_shra_qb (v4i8, imm0_7); +v4i8 __builtin_mips_shra_r_qb (v4i8, imm0_7); +v4i8 __builtin_mips_shra_qb (v4i8, i32); +v4i8 __builtin_mips_shra_r_qb (v4i8, i32); +v2i16 __builtin_mips_shrl_ph (v2i16, imm0_15); +v2i16 __builtin_mips_shrl_ph (v2i16, i32); +v2i16 __builtin_mips_subu_ph (v2i16, v2i16); +v2i16 __builtin_mips_subu_s_ph (v2i16, v2i16); +v4i8 __builtin_mips_subuh_qb (v4i8, v4i8); +v4i8 __builtin_mips_subuh_r_qb (v4i8, v4i8); +v2q15 __builtin_mips_addqh_ph (v2q15, v2q15); +v2q15 __builtin_mips_addqh_r_ph (v2q15, v2q15); +q31 __builtin_mips_addqh_w (q31, q31); +q31 __builtin_mips_addqh_r_w (q31, q31); +v2q15 __builtin_mips_subqh_ph (v2q15, v2q15); +v2q15 __builtin_mips_subqh_r_ph (v2q15, v2q15); +q31 __builtin_mips_subqh_w (q31, q31); +q31 __builtin_mips_subqh_r_w (q31, q31); +a64 __builtin_mips_dpax_w_ph (a64, v2i16, v2i16); +a64 __builtin_mips_dpsx_w_ph (a64, v2i16, v2i16); +a64 __builtin_mips_dpaqx_s_w_ph (a64, v2q15, v2q15); +a64 __builtin_mips_dpaqx_sa_w_ph (a64, v2q15, v2q15); +a64 __builtin_mips_dpsqx_s_w_ph (a64, v2q15, v2q15); +a64 __builtin_mips_dpsqx_sa_w_ph (a64, v2q15, v2q15); +@end smallexample + + +@node MIPS Paired-Single Support +@subsection MIPS Paired-Single Support + +The MIPS64 architecture includes a number of instructions that +operate on pairs of single-precision floating-point values. +Each pair is packed into a 64-bit floating-point register, +with one element being designated the ``upper half'' and +the other being designated the ``lower half''. + +GCC supports paired-single operations using both the generic +vector extensions (@pxref{Vector Extensions}) and a collection of +MIPS-specific built-in functions. Both kinds of support are +enabled by the @option{-mpaired-single} command-line option. + +The vector type associated with paired-single values is usually +called @code{v2sf}. It can be defined in C as follows: + +@smallexample +typedef float v2sf __attribute__ ((vector_size (8))); +@end smallexample + +@code{v2sf} values are initialized in the same way as aggregates. +For example: + +@smallexample +v2sf a = @{1.5, 9.1@}; +v2sf b; +float e, f; +b = (v2sf) @{e, f@}; +@end smallexample + +@emph{Note:} The CPU's endianness determines which value is stored in +the upper half of a register and which value is stored in the lower half. +On little-endian targets, the first value is the lower one and the second +value is the upper one. The opposite order applies to big-endian targets. +For example, the code above will set the lower half of @code{a} to +@code{1.5} on little-endian targets and @code{9.1} on big-endian targets. + +@node MIPS Loongson Built-in Functions +@subsection MIPS Loongson Built-in Functions + +GCC provides intrinsics to access the SIMD instructions provided by the +ST Microelectronics Loongson-2E and -2F processors. These intrinsics, +available after inclusion of the @code{loongson.h} header file, +operate on the following 64-bit vector types: + +@itemize +@item @code{uint8x8_t}, a vector of eight unsigned 8-bit integers; +@item @code{uint16x4_t}, a vector of four unsigned 16-bit integers; +@item @code{uint32x2_t}, a vector of two unsigned 32-bit integers; +@item @code{int8x8_t}, a vector of eight signed 8-bit integers; +@item @code{int16x4_t}, a vector of four signed 16-bit integers; +@item @code{int32x2_t}, a vector of two signed 32-bit integers. +@end itemize + +The intrinsics provided are listed below; each is named after the +machine instruction to which it corresponds, with suffixes added as +appropriate to distinguish intrinsics that expand to the same machine +instruction yet have different argument types. Refer to the architecture +documentation for a description of the functionality of each +instruction. + +@smallexample +int16x4_t packsswh (int32x2_t s, int32x2_t t); +int8x8_t packsshb (int16x4_t s, int16x4_t t); +uint8x8_t packushb (uint16x4_t s, uint16x4_t t); +uint32x2_t paddw_u (uint32x2_t s, uint32x2_t t); +uint16x4_t paddh_u (uint16x4_t s, uint16x4_t t); +uint8x8_t paddb_u (uint8x8_t s, uint8x8_t t); +int32x2_t paddw_s (int32x2_t s, int32x2_t t); +int16x4_t paddh_s (int16x4_t s, int16x4_t t); +int8x8_t paddb_s (int8x8_t s, int8x8_t t); +uint64_t paddd_u (uint64_t s, uint64_t t); +int64_t paddd_s (int64_t s, int64_t t); +int16x4_t paddsh (int16x4_t s, int16x4_t t); +int8x8_t paddsb (int8x8_t s, int8x8_t t); +uint16x4_t paddush (uint16x4_t s, uint16x4_t t); +uint8x8_t paddusb (uint8x8_t s, uint8x8_t t); +uint64_t pandn_ud (uint64_t s, uint64_t t); +uint32x2_t pandn_uw (uint32x2_t s, uint32x2_t t); +uint16x4_t pandn_uh (uint16x4_t s, uint16x4_t t); +uint8x8_t pandn_ub (uint8x8_t s, uint8x8_t t); +int64_t pandn_sd (int64_t s, int64_t t); +int32x2_t pandn_sw (int32x2_t s, int32x2_t t); +int16x4_t pandn_sh (int16x4_t s, int16x4_t t); +int8x8_t pandn_sb (int8x8_t s, int8x8_t t); +uint16x4_t pavgh (uint16x4_t s, uint16x4_t t); +uint8x8_t pavgb (uint8x8_t s, uint8x8_t t); +uint32x2_t pcmpeqw_u (uint32x2_t s, uint32x2_t t); +uint16x4_t pcmpeqh_u (uint16x4_t s, uint16x4_t t); +uint8x8_t pcmpeqb_u (uint8x8_t s, uint8x8_t t); +int32x2_t pcmpeqw_s (int32x2_t s, int32x2_t t); +int16x4_t pcmpeqh_s (int16x4_t s, int16x4_t t); +int8x8_t pcmpeqb_s (int8x8_t s, int8x8_t t); +uint32x2_t pcmpgtw_u (uint32x2_t s, uint32x2_t t); +uint16x4_t pcmpgth_u (uint16x4_t s, uint16x4_t t); +uint8x8_t pcmpgtb_u (uint8x8_t s, uint8x8_t t); +int32x2_t pcmpgtw_s (int32x2_t s, int32x2_t t); +int16x4_t pcmpgth_s (int16x4_t s, int16x4_t t); +int8x8_t pcmpgtb_s (int8x8_t s, int8x8_t t); +uint16x4_t pextrh_u (uint16x4_t s, int field); +int16x4_t pextrh_s (int16x4_t s, int field); +uint16x4_t pinsrh_0_u (uint16x4_t s, uint16x4_t t); +uint16x4_t pinsrh_1_u (uint16x4_t s, uint16x4_t t); +uint16x4_t pinsrh_2_u (uint16x4_t s, uint16x4_t t); +uint16x4_t pinsrh_3_u (uint16x4_t s, uint16x4_t t); +int16x4_t pinsrh_0_s (int16x4_t s, int16x4_t t); +int16x4_t pinsrh_1_s (int16x4_t s, int16x4_t t); +int16x4_t pinsrh_2_s (int16x4_t s, int16x4_t t); +int16x4_t pinsrh_3_s (int16x4_t s, int16x4_t t); +int32x2_t pmaddhw (int16x4_t s, int16x4_t t); +int16x4_t pmaxsh (int16x4_t s, int16x4_t t); +uint8x8_t pmaxub (uint8x8_t s, uint8x8_t t); +int16x4_t pminsh (int16x4_t s, int16x4_t t); +uint8x8_t pminub (uint8x8_t s, uint8x8_t t); +uint8x8_t pmovmskb_u (uint8x8_t s); +int8x8_t pmovmskb_s (int8x8_t s); +uint16x4_t pmulhuh (uint16x4_t s, uint16x4_t t); +int16x4_t pmulhh (int16x4_t s, int16x4_t t); +int16x4_t pmullh (int16x4_t s, int16x4_t t); +int64_t pmuluw (uint32x2_t s, uint32x2_t t); +uint8x8_t pasubub (uint8x8_t s, uint8x8_t t); +uint16x4_t biadd (uint8x8_t s); +uint16x4_t psadbh (uint8x8_t s, uint8x8_t t); +uint16x4_t pshufh_u (uint16x4_t dest, uint16x4_t s, uint8_t order); +int16x4_t pshufh_s (int16x4_t dest, int16x4_t s, uint8_t order); +uint16x4_t psllh_u (uint16x4_t s, uint8_t amount); +int16x4_t psllh_s (int16x4_t s, uint8_t amount); +uint32x2_t psllw_u (uint32x2_t s, uint8_t amount); +int32x2_t psllw_s (int32x2_t s, uint8_t amount); +uint16x4_t psrlh_u (uint16x4_t s, uint8_t amount); +int16x4_t psrlh_s (int16x4_t s, uint8_t amount); +uint32x2_t psrlw_u (uint32x2_t s, uint8_t amount); +int32x2_t psrlw_s (int32x2_t s, uint8_t amount); +uint16x4_t psrah_u (uint16x4_t s, uint8_t amount); +int16x4_t psrah_s (int16x4_t s, uint8_t amount); +uint32x2_t psraw_u (uint32x2_t s, uint8_t amount); +int32x2_t psraw_s (int32x2_t s, uint8_t amount); +uint32x2_t psubw_u (uint32x2_t s, uint32x2_t t); +uint16x4_t psubh_u (uint16x4_t s, uint16x4_t t); +uint8x8_t psubb_u (uint8x8_t s, uint8x8_t t); +int32x2_t psubw_s (int32x2_t s, int32x2_t t); +int16x4_t psubh_s (int16x4_t s, int16x4_t t); +int8x8_t psubb_s (int8x8_t s, int8x8_t t); +uint64_t psubd_u (uint64_t s, uint64_t t); +int64_t psubd_s (int64_t s, int64_t t); +int16x4_t psubsh (int16x4_t s, int16x4_t t); +int8x8_t psubsb (int8x8_t s, int8x8_t t); +uint16x4_t psubush (uint16x4_t s, uint16x4_t t); +uint8x8_t psubusb (uint8x8_t s, uint8x8_t t); +uint32x2_t punpckhwd_u (uint32x2_t s, uint32x2_t t); +uint16x4_t punpckhhw_u (uint16x4_t s, uint16x4_t t); +uint8x8_t punpckhbh_u (uint8x8_t s, uint8x8_t t); +int32x2_t punpckhwd_s (int32x2_t s, int32x2_t t); +int16x4_t punpckhhw_s (int16x4_t s, int16x4_t t); +int8x8_t punpckhbh_s (int8x8_t s, int8x8_t t); +uint32x2_t punpcklwd_u (uint32x2_t s, uint32x2_t t); +uint16x4_t punpcklhw_u (uint16x4_t s, uint16x4_t t); +uint8x8_t punpcklbh_u (uint8x8_t s, uint8x8_t t); +int32x2_t punpcklwd_s (int32x2_t s, int32x2_t t); +int16x4_t punpcklhw_s (int16x4_t s, int16x4_t t); +int8x8_t punpcklbh_s (int8x8_t s, int8x8_t t); +@end smallexample + +@menu +* Paired-Single Arithmetic:: +* Paired-Single Built-in Functions:: +* MIPS-3D Built-in Functions:: +@end menu + +@node Paired-Single Arithmetic +@subsubsection Paired-Single Arithmetic + +The table below lists the @code{v2sf} operations for which hardware +support exists. @code{a}, @code{b} and @code{c} are @code{v2sf} +values and @code{x} is an integral value. + +@multitable @columnfractions .50 .50 +@item C code @tab MIPS instruction +@item @code{a + b} @tab @code{add.ps} +@item @code{a - b} @tab @code{sub.ps} +@item @code{-a} @tab @code{neg.ps} +@item @code{a * b} @tab @code{mul.ps} +@item @code{a * b + c} @tab @code{madd.ps} +@item @code{a * b - c} @tab @code{msub.ps} +@item @code{-(a * b + c)} @tab @code{nmadd.ps} +@item @code{-(a * b - c)} @tab @code{nmsub.ps} +@item @code{x ? a : b} @tab @code{movn.ps}/@code{movz.ps} +@end multitable + +Note that the multiply-accumulate instructions can be disabled +using the command-line option @code{-mno-fused-madd}. + +@node Paired-Single Built-in Functions +@subsubsection Paired-Single Built-in Functions + +The following paired-single functions map directly to a particular +MIPS instruction. Please refer to the architecture specification +for details on what each instruction does. + +@table @code +@item v2sf __builtin_mips_pll_ps (v2sf, v2sf) +Pair lower lower (@code{pll.ps}). + +@item v2sf __builtin_mips_pul_ps (v2sf, v2sf) +Pair upper lower (@code{pul.ps}). + +@item v2sf __builtin_mips_plu_ps (v2sf, v2sf) +Pair lower upper (@code{plu.ps}). + +@item v2sf __builtin_mips_puu_ps (v2sf, v2sf) +Pair upper upper (@code{puu.ps}). + +@item v2sf __builtin_mips_cvt_ps_s (float, float) +Convert pair to paired single (@code{cvt.ps.s}). + +@item float __builtin_mips_cvt_s_pl (v2sf) +Convert pair lower to single (@code{cvt.s.pl}). + +@item float __builtin_mips_cvt_s_pu (v2sf) +Convert pair upper to single (@code{cvt.s.pu}). + +@item v2sf __builtin_mips_abs_ps (v2sf) +Absolute value (@code{abs.ps}). + +@item v2sf __builtin_mips_alnv_ps (v2sf, v2sf, int) +Align variable (@code{alnv.ps}). + +@emph{Note:} The value of the third parameter must be 0 or 4 +modulo 8, otherwise the result will be unpredictable. Please read the +instruction description for details. +@end table + +The following multi-instruction functions are also available. +In each case, @var{cond} can be any of the 16 floating-point conditions: +@code{f}, @code{un}, @code{eq}, @code{ueq}, @code{olt}, @code{ult}, +@code{ole}, @code{ule}, @code{sf}, @code{ngle}, @code{seq}, @code{ngl}, +@code{lt}, @code{nge}, @code{le} or @code{ngt}. + +@table @code +@item v2sf __builtin_mips_movt_c_@var{cond}_ps (v2sf @var{a}, v2sf @var{b}, v2sf @var{c}, v2sf @var{d}) +@itemx v2sf __builtin_mips_movf_c_@var{cond}_ps (v2sf @var{a}, v2sf @var{b}, v2sf @var{c}, v2sf @var{d}) +Conditional move based on floating point comparison (@code{c.@var{cond}.ps}, +@code{movt.ps}/@code{movf.ps}). + +The @code{movt} functions return the value @var{x} computed by: + +@smallexample +c.@var{cond}.ps @var{cc},@var{a},@var{b} +mov.ps @var{x},@var{c} +movt.ps @var{x},@var{d},@var{cc} +@end smallexample + +The @code{movf} functions are similar but use @code{movf.ps} instead +of @code{movt.ps}. + +@item int __builtin_mips_upper_c_@var{cond}_ps (v2sf @var{a}, v2sf @var{b}) +@itemx int __builtin_mips_lower_c_@var{cond}_ps (v2sf @var{a}, v2sf @var{b}) +Comparison of two paired-single values (@code{c.@var{cond}.ps}, +@code{bc1t}/@code{bc1f}). + +These functions compare @var{a} and @var{b} using @code{c.@var{cond}.ps} +and return either the upper or lower half of the result. For example: + +@smallexample +v2sf a, b; +if (__builtin_mips_upper_c_eq_ps (a, b)) + upper_halves_are_equal (); +else + upper_halves_are_unequal (); + +if (__builtin_mips_lower_c_eq_ps (a, b)) + lower_halves_are_equal (); +else + lower_halves_are_unequal (); +@end smallexample +@end table + +@node MIPS-3D Built-in Functions +@subsubsection MIPS-3D Built-in Functions + +The MIPS-3D Application-Specific Extension (ASE) includes additional +paired-single instructions that are designed to improve the performance +of 3D graphics operations. Support for these instructions is controlled +by the @option{-mips3d} command-line option. + +The functions listed below map directly to a particular MIPS-3D +instruction. Please refer to the architecture specification for +more details on what each instruction does. + +@table @code +@item v2sf __builtin_mips_addr_ps (v2sf, v2sf) +Reduction add (@code{addr.ps}). + +@item v2sf __builtin_mips_mulr_ps (v2sf, v2sf) +Reduction multiply (@code{mulr.ps}). + +@item v2sf __builtin_mips_cvt_pw_ps (v2sf) +Convert paired single to paired word (@code{cvt.pw.ps}). + +@item v2sf __builtin_mips_cvt_ps_pw (v2sf) +Convert paired word to paired single (@code{cvt.ps.pw}). + +@item float __builtin_mips_recip1_s (float) +@itemx double __builtin_mips_recip1_d (double) +@itemx v2sf __builtin_mips_recip1_ps (v2sf) +Reduced precision reciprocal (sequence step 1) (@code{recip1.@var{fmt}}). + +@item float __builtin_mips_recip2_s (float, float) +@itemx double __builtin_mips_recip2_d (double, double) +@itemx v2sf __builtin_mips_recip2_ps (v2sf, v2sf) +Reduced precision reciprocal (sequence step 2) (@code{recip2.@var{fmt}}). + +@item float __builtin_mips_rsqrt1_s (float) +@itemx double __builtin_mips_rsqrt1_d (double) +@itemx v2sf __builtin_mips_rsqrt1_ps (v2sf) +Reduced precision reciprocal square root (sequence step 1) +(@code{rsqrt1.@var{fmt}}). + +@item float __builtin_mips_rsqrt2_s (float, float) +@itemx double __builtin_mips_rsqrt2_d (double, double) +@itemx v2sf __builtin_mips_rsqrt2_ps (v2sf, v2sf) +Reduced precision reciprocal square root (sequence step 2) +(@code{rsqrt2.@var{fmt}}). +@end table + +The following multi-instruction functions are also available. +In each case, @var{cond} can be any of the 16 floating-point conditions: +@code{f}, @code{un}, @code{eq}, @code{ueq}, @code{olt}, @code{ult}, +@code{ole}, @code{ule}, @code{sf}, @code{ngle}, @code{seq}, +@code{ngl}, @code{lt}, @code{nge}, @code{le} or @code{ngt}. + +@table @code +@item int __builtin_mips_cabs_@var{cond}_s (float @var{a}, float @var{b}) +@itemx int __builtin_mips_cabs_@var{cond}_d (double @var{a}, double @var{b}) +Absolute comparison of two scalar values (@code{cabs.@var{cond}.@var{fmt}}, +@code{bc1t}/@code{bc1f}). + +These functions compare @var{a} and @var{b} using @code{cabs.@var{cond}.s} +or @code{cabs.@var{cond}.d} and return the result as a boolean value. +For example: + +@smallexample +float a, b; +if (__builtin_mips_cabs_eq_s (a, b)) + true (); +else + false (); +@end smallexample + +@item int __builtin_mips_upper_cabs_@var{cond}_ps (v2sf @var{a}, v2sf @var{b}) +@itemx int __builtin_mips_lower_cabs_@var{cond}_ps (v2sf @var{a}, v2sf @var{b}) +Absolute comparison of two paired-single values (@code{cabs.@var{cond}.ps}, +@code{bc1t}/@code{bc1f}). + +These functions compare @var{a} and @var{b} using @code{cabs.@var{cond}.ps} +and return either the upper or lower half of the result. For example: + +@smallexample +v2sf a, b; +if (__builtin_mips_upper_cabs_eq_ps (a, b)) + upper_halves_are_equal (); +else + upper_halves_are_unequal (); + +if (__builtin_mips_lower_cabs_eq_ps (a, b)) + lower_halves_are_equal (); +else + lower_halves_are_unequal (); +@end smallexample + +@item v2sf __builtin_mips_movt_cabs_@var{cond}_ps (v2sf @var{a}, v2sf @var{b}, v2sf @var{c}, v2sf @var{d}) +@itemx v2sf __builtin_mips_movf_cabs_@var{cond}_ps (v2sf @var{a}, v2sf @var{b}, v2sf @var{c}, v2sf @var{d}) +Conditional move based on absolute comparison (@code{cabs.@var{cond}.ps}, +@code{movt.ps}/@code{movf.ps}). + +The @code{movt} functions return the value @var{x} computed by: + +@smallexample +cabs.@var{cond}.ps @var{cc},@var{a},@var{b} +mov.ps @var{x},@var{c} +movt.ps @var{x},@var{d},@var{cc} +@end smallexample + +The @code{movf} functions are similar but use @code{movf.ps} instead +of @code{movt.ps}. + +@item int __builtin_mips_any_c_@var{cond}_ps (v2sf @var{a}, v2sf @var{b}) +@itemx int __builtin_mips_all_c_@var{cond}_ps (v2sf @var{a}, v2sf @var{b}) +@itemx int __builtin_mips_any_cabs_@var{cond}_ps (v2sf @var{a}, v2sf @var{b}) +@itemx int __builtin_mips_all_cabs_@var{cond}_ps (v2sf @var{a}, v2sf @var{b}) +Comparison of two paired-single values +(@code{c.@var{cond}.ps}/@code{cabs.@var{cond}.ps}, +@code{bc1any2t}/@code{bc1any2f}). + +These functions compare @var{a} and @var{b} using @code{c.@var{cond}.ps} +or @code{cabs.@var{cond}.ps}. The @code{any} forms return true if either +result is true and the @code{all} forms return true if both results are true. +For example: + +@smallexample +v2sf a, b; +if (__builtin_mips_any_c_eq_ps (a, b)) + one_is_true (); +else + both_are_false (); + +if (__builtin_mips_all_c_eq_ps (a, b)) + both_are_true (); +else + one_is_false (); +@end smallexample + +@item int __builtin_mips_any_c_@var{cond}_4s (v2sf @var{a}, v2sf @var{b}, v2sf @var{c}, v2sf @var{d}) +@itemx int __builtin_mips_all_c_@var{cond}_4s (v2sf @var{a}, v2sf @var{b}, v2sf @var{c}, v2sf @var{d}) +@itemx int __builtin_mips_any_cabs_@var{cond}_4s (v2sf @var{a}, v2sf @var{b}, v2sf @var{c}, v2sf @var{d}) +@itemx int __builtin_mips_all_cabs_@var{cond}_4s (v2sf @var{a}, v2sf @var{b}, v2sf @var{c}, v2sf @var{d}) +Comparison of four paired-single values +(@code{c.@var{cond}.ps}/@code{cabs.@var{cond}.ps}, +@code{bc1any4t}/@code{bc1any4f}). + +These functions use @code{c.@var{cond}.ps} or @code{cabs.@var{cond}.ps} +to compare @var{a} with @var{b} and to compare @var{c} with @var{d}. +The @code{any} forms return true if any of the four results are true +and the @code{all} forms return true if all four results are true. +For example: + +@smallexample +v2sf a, b, c, d; +if (__builtin_mips_any_c_eq_4s (a, b, c, d)) + some_are_true (); +else + all_are_false (); + +if (__builtin_mips_all_c_eq_4s (a, b, c, d)) + all_are_true (); +else + some_are_false (); +@end smallexample +@end table + +@node picoChip Built-in Functions +@subsection picoChip Built-in Functions + +GCC provides an interface to selected machine instructions from the +picoChip instruction set. + +@table @code +@item int __builtin_sbc (int @var{value}) +Sign bit count. Return the number of consecutive bits in @var{value} +which have the same value as the sign-bit. The result is the number of +leading sign bits minus one, giving the number of redundant sign bits in +@var{value}. + +@item int __builtin_byteswap (int @var{value}) +Byte swap. Return the result of swapping the upper and lower bytes of +@var{value}. + +@item int __builtin_brev (int @var{value}) +Bit reversal. Return the result of reversing the bits in +@var{value}. Bit 15 is swapped with bit 0, bit 14 is swapped with bit 1, +and so on. + +@item int __builtin_adds (int @var{x}, int @var{y}) +Saturating addition. Return the result of adding @var{x} and @var{y}, +storing the value 32767 if the result overflows. + +@item int __builtin_subs (int @var{x}, int @var{y}) +Saturating subtraction. Return the result of subtracting @var{y} from +@var{x}, storing the value @minus{}32768 if the result overflows. + +@item void __builtin_halt (void) +Halt. The processor will stop execution. This built-in is useful for +implementing assertions. + +@end table + +@node Other MIPS Built-in Functions +@subsection Other MIPS Built-in Functions + +GCC provides other MIPS-specific built-in functions: + +@table @code +@item void __builtin_mips_cache (int @var{op}, const volatile void *@var{addr}) +Insert a @samp{cache} instruction with operands @var{op} and @var{addr}. +GCC defines the preprocessor macro @code{___GCC_HAVE_BUILTIN_MIPS_CACHE} +when this function is available. +@end table + +@node PowerPC AltiVec/VSX Built-in Functions +@subsection PowerPC AltiVec Built-in Functions + +GCC provides an interface for the PowerPC family of processors to access +the AltiVec operations described in Motorola's AltiVec Programming +Interface Manual. The interface is made available by including +@code{<altivec.h>} and using @option{-maltivec} and +@option{-mabi=altivec}. The interface supports the following vector +types. + +@smallexample +vector unsigned char +vector signed char +vector bool char + +vector unsigned short +vector signed short +vector bool short +vector pixel + +vector unsigned int +vector signed int +vector bool int +vector float +@end smallexample + +If @option{-mvsx} is used the following additional vector types are +implemented. + +@smallexample +vector unsigned long +vector signed long +vector double +@end smallexample + +The long types are only implemented for 64-bit code generation, and +the long type is only used in the floating point/integer conversion +instructions. + +GCC's implementation of the high-level language interface available from +C and C++ code differs from Motorola's documentation in several ways. + +@itemize @bullet + +@item +A vector constant is a list of constant expressions within curly braces. + +@item +A vector initializer requires no cast if the vector constant is of the +same type as the variable it is initializing. + +@item +If @code{signed} or @code{unsigned} is omitted, the signedness of the +vector type is the default signedness of the base type. The default +varies depending on the operating system, so a portable program should +always specify the signedness. + +@item +Compiling with @option{-maltivec} adds keywords @code{__vector}, +@code{vector}, @code{__pixel}, @code{pixel}, @code{__bool} and +@code{bool}. When compiling ISO C, the context-sensitive substitution +of the keywords @code{vector}, @code{pixel} and @code{bool} is +disabled. To use them, you must include @code{<altivec.h>} instead. + +@item +GCC allows using a @code{typedef} name as the type specifier for a +vector type. + +@item +For C, overloaded functions are implemented with macros so the following +does not work: + +@smallexample + vec_add ((vector signed int)@{1, 2, 3, 4@}, foo); +@end smallexample + +Since @code{vec_add} is a macro, the vector constant in the example +is treated as four separate arguments. Wrap the entire argument in +parentheses for this to work. +@end itemize + +@emph{Note:} Only the @code{<altivec.h>} interface is supported. +Internally, GCC uses built-in functions to achieve the functionality in +the aforementioned header file, but they are not supported and are +subject to change without notice. + +The following interfaces are supported for the generic and specific +AltiVec operations and the AltiVec predicates. In cases where there +is a direct mapping between generic and specific operations, only the +generic names are shown here, although the specific operations can also +be used. + +Arguments that are documented as @code{const int} require literal +integral values within the range required for that operation. + +@smallexample +vector signed char vec_abs (vector signed char); +vector signed short vec_abs (vector signed short); +vector signed int vec_abs (vector signed int); +vector float vec_abs (vector float); + +vector signed char vec_abss (vector signed char); +vector signed short vec_abss (vector signed short); +vector signed int vec_abss (vector signed int); + +vector signed char vec_add (vector bool char, vector signed char); +vector signed char vec_add (vector signed char, vector bool char); +vector signed char vec_add (vector signed char, vector signed char); +vector unsigned char vec_add (vector bool char, vector unsigned char); +vector unsigned char vec_add (vector unsigned char, vector bool char); +vector unsigned char vec_add (vector unsigned char, + vector unsigned char); +vector signed short vec_add (vector bool short, vector signed short); +vector signed short vec_add (vector signed short, vector bool short); +vector signed short vec_add (vector signed short, vector signed short); +vector unsigned short vec_add (vector bool short, + vector unsigned short); +vector unsigned short vec_add (vector unsigned short, + vector bool short); +vector unsigned short vec_add (vector unsigned short, + vector unsigned short); +vector signed int vec_add (vector bool int, vector signed int); +vector signed int vec_add (vector signed int, vector bool int); +vector signed int vec_add (vector signed int, vector signed int); +vector unsigned int vec_add (vector bool int, vector unsigned int); +vector unsigned int vec_add (vector unsigned int, vector bool int); +vector unsigned int vec_add (vector unsigned int, vector unsigned int); +vector float vec_add (vector float, vector float); + +vector float vec_vaddfp (vector float, vector float); + +vector signed int vec_vadduwm (vector bool int, vector signed int); +vector signed int vec_vadduwm (vector signed int, vector bool int); +vector signed int vec_vadduwm (vector signed int, vector signed int); +vector unsigned int vec_vadduwm (vector bool int, vector unsigned int); +vector unsigned int vec_vadduwm (vector unsigned int, vector bool int); +vector unsigned int vec_vadduwm (vector unsigned int, + vector unsigned int); + +vector signed short vec_vadduhm (vector bool short, + vector signed short); +vector signed short vec_vadduhm (vector signed short, + vector bool short); +vector signed short vec_vadduhm (vector signed short, + vector signed short); +vector unsigned short vec_vadduhm (vector bool short, + vector unsigned short); +vector unsigned short vec_vadduhm (vector unsigned short, + vector bool short); +vector unsigned short vec_vadduhm (vector unsigned short, + vector unsigned short); + +vector signed char vec_vaddubm (vector bool char, vector signed char); +vector signed char vec_vaddubm (vector signed char, vector bool char); +vector signed char vec_vaddubm (vector signed char, vector signed char); +vector unsigned char vec_vaddubm (vector bool char, + vector unsigned char); +vector unsigned char vec_vaddubm (vector unsigned char, + vector bool char); +vector unsigned char vec_vaddubm (vector unsigned char, + vector unsigned char); + +vector unsigned int vec_addc (vector unsigned int, vector unsigned int); + +vector unsigned char vec_adds (vector bool char, vector unsigned char); +vector unsigned char vec_adds (vector unsigned char, vector bool char); +vector unsigned char vec_adds (vector unsigned char, + vector unsigned char); +vector signed char vec_adds (vector bool char, vector signed char); +vector signed char vec_adds (vector signed char, vector bool char); +vector signed char vec_adds (vector signed char, vector signed char); +vector unsigned short vec_adds (vector bool short, + vector unsigned short); +vector unsigned short vec_adds (vector unsigned short, + vector bool short); +vector unsigned short vec_adds (vector unsigned short, + vector unsigned short); +vector signed short vec_adds (vector bool short, vector signed short); +vector signed short vec_adds (vector signed short, vector bool short); +vector signed short vec_adds (vector signed short, vector signed short); +vector unsigned int vec_adds (vector bool int, vector unsigned int); +vector unsigned int vec_adds (vector unsigned int, vector bool int); +vector unsigned int vec_adds (vector unsigned int, vector unsigned int); +vector signed int vec_adds (vector bool int, vector signed int); +vector signed int vec_adds (vector signed int, vector bool int); +vector signed int vec_adds (vector signed int, vector signed int); + +vector signed int vec_vaddsws (vector bool int, vector signed int); +vector signed int vec_vaddsws (vector signed int, vector bool int); +vector signed int vec_vaddsws (vector signed int, vector signed int); + +vector unsigned int vec_vadduws (vector bool int, vector unsigned int); +vector unsigned int vec_vadduws (vector unsigned int, vector bool int); +vector unsigned int vec_vadduws (vector unsigned int, + vector unsigned int); + +vector signed short vec_vaddshs (vector bool short, + vector signed short); +vector signed short vec_vaddshs (vector signed short, + vector bool short); +vector signed short vec_vaddshs (vector signed short, + vector signed short); + +vector unsigned short vec_vadduhs (vector bool short, + vector unsigned short); +vector unsigned short vec_vadduhs (vector unsigned short, + vector bool short); +vector unsigned short vec_vadduhs (vector unsigned short, + vector unsigned short); + +vector signed char vec_vaddsbs (vector bool char, vector signed char); +vector signed char vec_vaddsbs (vector signed char, vector bool char); +vector signed char vec_vaddsbs (vector signed char, vector signed char); + +vector unsigned char vec_vaddubs (vector bool char, + vector unsigned char); +vector unsigned char vec_vaddubs (vector unsigned char, + vector bool char); +vector unsigned char vec_vaddubs (vector unsigned char, + vector unsigned char); + +vector float vec_and (vector float, vector float); +vector float vec_and (vector float, vector bool int); +vector float vec_and (vector bool int, vector float); +vector bool int vec_and (vector bool int, vector bool int); +vector signed int vec_and (vector bool int, vector signed int); +vector signed int vec_and (vector signed int, vector bool int); +vector signed int vec_and (vector signed int, vector signed int); +vector unsigned int vec_and (vector bool int, vector unsigned int); +vector unsigned int vec_and (vector unsigned int, vector bool int); +vector unsigned int vec_and (vector unsigned int, vector unsigned int); +vector bool short vec_and (vector bool short, vector bool short); +vector signed short vec_and (vector bool short, vector signed short); +vector signed short vec_and (vector signed short, vector bool short); +vector signed short vec_and (vector signed short, vector signed short); +vector unsigned short vec_and (vector bool short, + vector unsigned short); +vector unsigned short vec_and (vector unsigned short, + vector bool short); +vector unsigned short vec_and (vector unsigned short, + vector unsigned short); +vector signed char vec_and (vector bool char, vector signed char); +vector bool char vec_and (vector bool char, vector bool char); +vector signed char vec_and (vector signed char, vector bool char); +vector signed char vec_and (vector signed char, vector signed char); +vector unsigned char vec_and (vector bool char, vector unsigned char); +vector unsigned char vec_and (vector unsigned char, vector bool char); +vector unsigned char vec_and (vector unsigned char, + vector unsigned char); + +vector float vec_andc (vector float, vector float); +vector float vec_andc (vector float, vector bool int); +vector float vec_andc (vector bool int, vector float); +vector bool int vec_andc (vector bool int, vector bool int); +vector signed int vec_andc (vector bool int, vector signed int); +vector signed int vec_andc (vector signed int, vector bool int); +vector signed int vec_andc (vector signed int, vector signed int); +vector unsigned int vec_andc (vector bool int, vector unsigned int); +vector unsigned int vec_andc (vector unsigned int, vector bool int); +vector unsigned int vec_andc (vector unsigned int, vector unsigned int); +vector bool short vec_andc (vector bool short, vector bool short); +vector signed short vec_andc (vector bool short, vector signed short); +vector signed short vec_andc (vector signed short, vector bool short); +vector signed short vec_andc (vector signed short, vector signed short); +vector unsigned short vec_andc (vector bool short, + vector unsigned short); +vector unsigned short vec_andc (vector unsigned short, + vector bool short); +vector unsigned short vec_andc (vector unsigned short, + vector unsigned short); +vector signed char vec_andc (vector bool char, vector signed char); +vector bool char vec_andc (vector bool char, vector bool char); +vector signed char vec_andc (vector signed char, vector bool char); +vector signed char vec_andc (vector signed char, vector signed char); +vector unsigned char vec_andc (vector bool char, vector unsigned char); +vector unsigned char vec_andc (vector unsigned char, vector bool char); +vector unsigned char vec_andc (vector unsigned char, + vector unsigned char); + +vector unsigned char vec_avg (vector unsigned char, + vector unsigned char); +vector signed char vec_avg (vector signed char, vector signed char); +vector unsigned short vec_avg (vector unsigned short, + vector unsigned short); +vector signed short vec_avg (vector signed short, vector signed short); +vector unsigned int vec_avg (vector unsigned int, vector unsigned int); +vector signed int vec_avg (vector signed int, vector signed int); + +vector signed int vec_vavgsw (vector signed int, vector signed int); + +vector unsigned int vec_vavguw (vector unsigned int, + vector unsigned int); + +vector signed short vec_vavgsh (vector signed short, + vector signed short); + +vector unsigned short vec_vavguh (vector unsigned short, + vector unsigned short); + +vector signed char vec_vavgsb (vector signed char, vector signed char); + +vector unsigned char vec_vavgub (vector unsigned char, + vector unsigned char); + +vector float vec_copysign (vector float); + +vector float vec_ceil (vector float); + +vector signed int vec_cmpb (vector float, vector float); + +vector bool char vec_cmpeq (vector signed char, vector signed char); +vector bool char vec_cmpeq (vector unsigned char, vector unsigned char); +vector bool short vec_cmpeq (vector signed short, vector signed short); +vector bool short vec_cmpeq (vector unsigned short, + vector unsigned short); +vector bool int vec_cmpeq (vector signed int, vector signed int); +vector bool int vec_cmpeq (vector unsigned int, vector unsigned int); +vector bool int vec_cmpeq (vector float, vector float); + +vector bool int vec_vcmpeqfp (vector float, vector float); + +vector bool int vec_vcmpequw (vector signed int, vector signed int); +vector bool int vec_vcmpequw (vector unsigned int, vector unsigned int); + +vector bool short vec_vcmpequh (vector signed short, + vector signed short); +vector bool short vec_vcmpequh (vector unsigned short, + vector unsigned short); + +vector bool char vec_vcmpequb (vector signed char, vector signed char); +vector bool char vec_vcmpequb (vector unsigned char, + vector unsigned char); + +vector bool int vec_cmpge (vector float, vector float); + +vector bool char vec_cmpgt (vector unsigned char, vector unsigned char); +vector bool char vec_cmpgt (vector signed char, vector signed char); +vector bool short vec_cmpgt (vector unsigned short, + vector unsigned short); +vector bool short vec_cmpgt (vector signed short, vector signed short); +vector bool int vec_cmpgt (vector unsigned int, vector unsigned int); +vector bool int vec_cmpgt (vector signed int, vector signed int); +vector bool int vec_cmpgt (vector float, vector float); + +vector bool int vec_vcmpgtfp (vector float, vector float); + +vector bool int vec_vcmpgtsw (vector signed int, vector signed int); + +vector bool int vec_vcmpgtuw (vector unsigned int, vector unsigned int); + +vector bool short vec_vcmpgtsh (vector signed short, + vector signed short); + +vector bool short vec_vcmpgtuh (vector unsigned short, + vector unsigned short); + +vector bool char vec_vcmpgtsb (vector signed char, vector signed char); + +vector bool char vec_vcmpgtub (vector unsigned char, + vector unsigned char); + +vector bool int vec_cmple (vector float, vector float); + +vector bool char vec_cmplt (vector unsigned char, vector unsigned char); +vector bool char vec_cmplt (vector signed char, vector signed char); +vector bool short vec_cmplt (vector unsigned short, + vector unsigned short); +vector bool short vec_cmplt (vector signed short, vector signed short); +vector bool int vec_cmplt (vector unsigned int, vector unsigned int); +vector bool int vec_cmplt (vector signed int, vector signed int); +vector bool int vec_cmplt (vector float, vector float); + +vector float vec_ctf (vector unsigned int, const int); +vector float vec_ctf (vector signed int, const int); + +vector float vec_vcfsx (vector signed int, const int); + +vector float vec_vcfux (vector unsigned int, const int); + +vector signed int vec_cts (vector float, const int); + +vector unsigned int vec_ctu (vector float, const int); + +void vec_dss (const int); + +void vec_dssall (void); + +void vec_dst (const vector unsigned char *, int, const int); +void vec_dst (const vector signed char *, int, const int); +void vec_dst (const vector bool char *, int, const int); +void vec_dst (const vector unsigned short *, int, const int); +void vec_dst (const vector signed short *, int, const int); +void vec_dst (const vector bool short *, int, const int); +void vec_dst (const vector pixel *, int, const int); +void vec_dst (const vector unsigned int *, int, const int); +void vec_dst (const vector signed int *, int, const int); +void vec_dst (const vector bool int *, int, const int); +void vec_dst (const vector float *, int, const int); +void vec_dst (const unsigned char *, int, const int); +void vec_dst (const signed char *, int, const int); +void vec_dst (const unsigned short *, int, const int); +void vec_dst (const short *, int, const int); +void vec_dst (const unsigned int *, int, const int); +void vec_dst (const int *, int, const int); +void vec_dst (const unsigned long *, int, const int); +void vec_dst (const long *, int, const int); +void vec_dst (const float *, int, const int); + +void vec_dstst (const vector unsigned char *, int, const int); +void vec_dstst (const vector signed char *, int, const int); +void vec_dstst (const vector bool char *, int, const int); +void vec_dstst (const vector unsigned short *, int, const int); +void vec_dstst (const vector signed short *, int, const int); +void vec_dstst (const vector bool short *, int, const int); +void vec_dstst (const vector pixel *, int, const int); +void vec_dstst (const vector unsigned int *, int, const int); +void vec_dstst (const vector signed int *, int, const int); +void vec_dstst (const vector bool int *, int, const int); +void vec_dstst (const vector float *, int, const int); +void vec_dstst (const unsigned char *, int, const int); +void vec_dstst (const signed char *, int, const int); +void vec_dstst (const unsigned short *, int, const int); +void vec_dstst (const short *, int, const int); +void vec_dstst (const unsigned int *, int, const int); +void vec_dstst (const int *, int, const int); +void vec_dstst (const unsigned long *, int, const int); +void vec_dstst (const long *, int, const int); +void vec_dstst (const float *, int, const int); + +void vec_dststt (const vector unsigned char *, int, const int); +void vec_dststt (const vector signed char *, int, const int); +void vec_dststt (const vector bool char *, int, const int); +void vec_dststt (const vector unsigned short *, int, const int); +void vec_dststt (const vector signed short *, int, const int); +void vec_dststt (const vector bool short *, int, const int); +void vec_dststt (const vector pixel *, int, const int); +void vec_dststt (const vector unsigned int *, int, const int); +void vec_dststt (const vector signed int *, int, const int); +void vec_dststt (const vector bool int *, int, const int); +void vec_dststt (const vector float *, int, const int); +void vec_dststt (const unsigned char *, int, const int); +void vec_dststt (const signed char *, int, const int); +void vec_dststt (const unsigned short *, int, const int); +void vec_dststt (const short *, int, const int); +void vec_dststt (const unsigned int *, int, const int); +void vec_dststt (const int *, int, const int); +void vec_dststt (const unsigned long *, int, const int); +void vec_dststt (const long *, int, const int); +void vec_dststt (const float *, int, const int); + +void vec_dstt (const vector unsigned char *, int, const int); +void vec_dstt (const vector signed char *, int, const int); +void vec_dstt (const vector bool char *, int, const int); +void vec_dstt (const vector unsigned short *, int, const int); +void vec_dstt (const vector signed short *, int, const int); +void vec_dstt (const vector bool short *, int, const int); +void vec_dstt (const vector pixel *, int, const int); +void vec_dstt (const vector unsigned int *, int, const int); +void vec_dstt (const vector signed int *, int, const int); +void vec_dstt (const vector bool int *, int, const int); +void vec_dstt (const vector float *, int, const int); +void vec_dstt (const unsigned char *, int, const int); +void vec_dstt (const signed char *, int, const int); +void vec_dstt (const unsigned short *, int, const int); +void vec_dstt (const short *, int, const int); +void vec_dstt (const unsigned int *, int, const int); +void vec_dstt (const int *, int, const int); +void vec_dstt (const unsigned long *, int, const int); +void vec_dstt (const long *, int, const int); +void vec_dstt (const float *, int, const int); + +vector float vec_expte (vector float); + +vector float vec_floor (vector float); + +vector float vec_ld (int, const vector float *); +vector float vec_ld (int, const float *); +vector bool int vec_ld (int, const vector bool int *); +vector signed int vec_ld (int, const vector signed int *); +vector signed int vec_ld (int, const int *); +vector signed int vec_ld (int, const long *); +vector unsigned int vec_ld (int, const vector unsigned int *); +vector unsigned int vec_ld (int, const unsigned int *); +vector unsigned int vec_ld (int, const unsigned long *); +vector bool short vec_ld (int, const vector bool short *); +vector pixel vec_ld (int, const vector pixel *); +vector signed short vec_ld (int, const vector signed short *); +vector signed short vec_ld (int, const short *); +vector unsigned short vec_ld (int, const vector unsigned short *); +vector unsigned short vec_ld (int, const unsigned short *); +vector bool char vec_ld (int, const vector bool char *); +vector signed char vec_ld (int, const vector signed char *); +vector signed char vec_ld (int, const signed char *); +vector unsigned char vec_ld (int, const vector unsigned char *); +vector unsigned char vec_ld (int, const unsigned char *); + +vector signed char vec_lde (int, const signed char *); +vector unsigned char vec_lde (int, const unsigned char *); +vector signed short vec_lde (int, const short *); +vector unsigned short vec_lde (int, const unsigned short *); +vector float vec_lde (int, const float *); +vector signed int vec_lde (int, const int *); +vector unsigned int vec_lde (int, const unsigned int *); +vector signed int vec_lde (int, const long *); +vector unsigned int vec_lde (int, const unsigned long *); + +vector float vec_lvewx (int, float *); +vector signed int vec_lvewx (int, int *); +vector unsigned int vec_lvewx (int, unsigned int *); +vector signed int vec_lvewx (int, long *); +vector unsigned int vec_lvewx (int, unsigned long *); + +vector signed short vec_lvehx (int, short *); +vector unsigned short vec_lvehx (int, unsigned short *); + +vector signed char vec_lvebx (int, char *); +vector unsigned char vec_lvebx (int, unsigned char *); + +vector float vec_ldl (int, const vector float *); +vector float vec_ldl (int, const float *); +vector bool int vec_ldl (int, const vector bool int *); +vector signed int vec_ldl (int, const vector signed int *); +vector signed int vec_ldl (int, const int *); +vector signed int vec_ldl (int, const long *); +vector unsigned int vec_ldl (int, const vector unsigned int *); +vector unsigned int vec_ldl (int, const unsigned int *); +vector unsigned int vec_ldl (int, const unsigned long *); +vector bool short vec_ldl (int, const vector bool short *); +vector pixel vec_ldl (int, const vector pixel *); +vector signed short vec_ldl (int, const vector signed short *); +vector signed short vec_ldl (int, const short *); +vector unsigned short vec_ldl (int, const vector unsigned short *); +vector unsigned short vec_ldl (int, const unsigned short *); +vector bool char vec_ldl (int, const vector bool char *); +vector signed char vec_ldl (int, const vector signed char *); +vector signed char vec_ldl (int, const signed char *); +vector unsigned char vec_ldl (int, const vector unsigned char *); +vector unsigned char vec_ldl (int, const unsigned char *); + +vector float vec_loge (vector float); + +vector unsigned char vec_lvsl (int, const volatile unsigned char *); +vector unsigned char vec_lvsl (int, const volatile signed char *); +vector unsigned char vec_lvsl (int, const volatile unsigned short *); +vector unsigned char vec_lvsl (int, const volatile short *); +vector unsigned char vec_lvsl (int, const volatile unsigned int *); +vector unsigned char vec_lvsl (int, const volatile int *); +vector unsigned char vec_lvsl (int, const volatile unsigned long *); +vector unsigned char vec_lvsl (int, const volatile long *); +vector unsigned char vec_lvsl (int, const volatile float *); + +vector unsigned char vec_lvsr (int, const volatile unsigned char *); +vector unsigned char vec_lvsr (int, const volatile signed char *); +vector unsigned char vec_lvsr (int, const volatile unsigned short *); +vector unsigned char vec_lvsr (int, const volatile short *); +vector unsigned char vec_lvsr (int, const volatile unsigned int *); +vector unsigned char vec_lvsr (int, const volatile int *); +vector unsigned char vec_lvsr (int, const volatile unsigned long *); +vector unsigned char vec_lvsr (int, const volatile long *); +vector unsigned char vec_lvsr (int, const volatile float *); + +vector float vec_madd (vector float, vector float, vector float); + +vector signed short vec_madds (vector signed short, + vector signed short, + vector signed short); + +vector unsigned char vec_max (vector bool char, vector unsigned char); +vector unsigned char vec_max (vector unsigned char, vector bool char); +vector unsigned char vec_max (vector unsigned char, + vector unsigned char); +vector signed char vec_max (vector bool char, vector signed char); +vector signed char vec_max (vector signed char, vector bool char); +vector signed char vec_max (vector signed char, vector signed char); +vector unsigned short vec_max (vector bool short, + vector unsigned short); +vector unsigned short vec_max (vector unsigned short, + vector bool short); +vector unsigned short vec_max (vector unsigned short, + vector unsigned short); +vector signed short vec_max (vector bool short, vector signed short); +vector signed short vec_max (vector signed short, vector bool short); +vector signed short vec_max (vector signed short, vector signed short); +vector unsigned int vec_max (vector bool int, vector unsigned int); +vector unsigned int vec_max (vector unsigned int, vector bool int); +vector unsigned int vec_max (vector unsigned int, vector unsigned int); +vector signed int vec_max (vector bool int, vector signed int); +vector signed int vec_max (vector signed int, vector bool int); +vector signed int vec_max (vector signed int, vector signed int); +vector float vec_max (vector float, vector float); + +vector float vec_vmaxfp (vector float, vector float); + +vector signed int vec_vmaxsw (vector bool int, vector signed int); +vector signed int vec_vmaxsw (vector signed int, vector bool int); +vector signed int vec_vmaxsw (vector signed int, vector signed int); + +vector unsigned int vec_vmaxuw (vector bool int, vector unsigned int); +vector unsigned int vec_vmaxuw (vector unsigned int, vector bool int); +vector unsigned int vec_vmaxuw (vector unsigned int, + vector unsigned int); + +vector signed short vec_vmaxsh (vector bool short, vector signed short); +vector signed short vec_vmaxsh (vector signed short, vector bool short); +vector signed short vec_vmaxsh (vector signed short, + vector signed short); + +vector unsigned short vec_vmaxuh (vector bool short, + vector unsigned short); +vector unsigned short vec_vmaxuh (vector unsigned short, + vector bool short); +vector unsigned short vec_vmaxuh (vector unsigned short, + vector unsigned short); + +vector signed char vec_vmaxsb (vector bool char, vector signed char); +vector signed char vec_vmaxsb (vector signed char, vector bool char); +vector signed char vec_vmaxsb (vector signed char, vector signed char); + +vector unsigned char vec_vmaxub (vector bool char, + vector unsigned char); +vector unsigned char vec_vmaxub (vector unsigned char, + vector bool char); +vector unsigned char vec_vmaxub (vector unsigned char, + vector unsigned char); + +vector bool char vec_mergeh (vector bool char, vector bool char); +vector signed char vec_mergeh (vector signed char, vector signed char); +vector unsigned char vec_mergeh (vector unsigned char, + vector unsigned char); +vector bool short vec_mergeh (vector bool short, vector bool short); +vector pixel vec_mergeh (vector pixel, vector pixel); +vector signed short vec_mergeh (vector signed short, + vector signed short); +vector unsigned short vec_mergeh (vector unsigned short, + vector unsigned short); +vector float vec_mergeh (vector float, vector float); +vector bool int vec_mergeh (vector bool int, vector bool int); +vector signed int vec_mergeh (vector signed int, vector signed int); +vector unsigned int vec_mergeh (vector unsigned int, + vector unsigned int); + +vector float vec_vmrghw (vector float, vector float); +vector bool int vec_vmrghw (vector bool int, vector bool int); +vector signed int vec_vmrghw (vector signed int, vector signed int); +vector unsigned int vec_vmrghw (vector unsigned int, + vector unsigned int); + +vector bool short vec_vmrghh (vector bool short, vector bool short); +vector signed short vec_vmrghh (vector signed short, + vector signed short); +vector unsigned short vec_vmrghh (vector unsigned short, + vector unsigned short); +vector pixel vec_vmrghh (vector pixel, vector pixel); + +vector bool char vec_vmrghb (vector bool char, vector bool char); +vector signed char vec_vmrghb (vector signed char, vector signed char); +vector unsigned char vec_vmrghb (vector unsigned char, + vector unsigned char); + +vector bool char vec_mergel (vector bool char, vector bool char); +vector signed char vec_mergel (vector signed char, vector signed char); +vector unsigned char vec_mergel (vector unsigned char, + vector unsigned char); +vector bool short vec_mergel (vector bool short, vector bool short); +vector pixel vec_mergel (vector pixel, vector pixel); +vector signed short vec_mergel (vector signed short, + vector signed short); +vector unsigned short vec_mergel (vector unsigned short, + vector unsigned short); +vector float vec_mergel (vector float, vector float); +vector bool int vec_mergel (vector bool int, vector bool int); +vector signed int vec_mergel (vector signed int, vector signed int); +vector unsigned int vec_mergel (vector unsigned int, + vector unsigned int); + +vector float vec_vmrglw (vector float, vector float); +vector signed int vec_vmrglw (vector signed int, vector signed int); +vector unsigned int vec_vmrglw (vector unsigned int, + vector unsigned int); +vector bool int vec_vmrglw (vector bool int, vector bool int); + +vector bool short vec_vmrglh (vector bool short, vector bool short); +vector signed short vec_vmrglh (vector signed short, + vector signed short); +vector unsigned short vec_vmrglh (vector unsigned short, + vector unsigned short); +vector pixel vec_vmrglh (vector pixel, vector pixel); + +vector bool char vec_vmrglb (vector bool char, vector bool char); +vector signed char vec_vmrglb (vector signed char, vector signed char); +vector unsigned char vec_vmrglb (vector unsigned char, + vector unsigned char); + +vector unsigned short vec_mfvscr (void); + +vector unsigned char vec_min (vector bool char, vector unsigned char); +vector unsigned char vec_min (vector unsigned char, vector bool char); +vector unsigned char vec_min (vector unsigned char, + vector unsigned char); +vector signed char vec_min (vector bool char, vector signed char); +vector signed char vec_min (vector signed char, vector bool char); +vector signed char vec_min (vector signed char, vector signed char); +vector unsigned short vec_min (vector bool short, + vector unsigned short); +vector unsigned short vec_min (vector unsigned short, + vector bool short); +vector unsigned short vec_min (vector unsigned short, + vector unsigned short); +vector signed short vec_min (vector bool short, vector signed short); +vector signed short vec_min (vector signed short, vector bool short); +vector signed short vec_min (vector signed short, vector signed short); +vector unsigned int vec_min (vector bool int, vector unsigned int); +vector unsigned int vec_min (vector unsigned int, vector bool int); +vector unsigned int vec_min (vector unsigned int, vector unsigned int); +vector signed int vec_min (vector bool int, vector signed int); +vector signed int vec_min (vector signed int, vector bool int); +vector signed int vec_min (vector signed int, vector signed int); +vector float vec_min (vector float, vector float); + +vector float vec_vminfp (vector float, vector float); + +vector signed int vec_vminsw (vector bool int, vector signed int); +vector signed int vec_vminsw (vector signed int, vector bool int); +vector signed int vec_vminsw (vector signed int, vector signed int); + +vector unsigned int vec_vminuw (vector bool int, vector unsigned int); +vector unsigned int vec_vminuw (vector unsigned int, vector bool int); +vector unsigned int vec_vminuw (vector unsigned int, + vector unsigned int); + +vector signed short vec_vminsh (vector bool short, vector signed short); +vector signed short vec_vminsh (vector signed short, vector bool short); +vector signed short vec_vminsh (vector signed short, + vector signed short); + +vector unsigned short vec_vminuh (vector bool short, + vector unsigned short); +vector unsigned short vec_vminuh (vector unsigned short, + vector bool short); +vector unsigned short vec_vminuh (vector unsigned short, + vector unsigned short); + +vector signed char vec_vminsb (vector bool char, vector signed char); +vector signed char vec_vminsb (vector signed char, vector bool char); +vector signed char vec_vminsb (vector signed char, vector signed char); + +vector unsigned char vec_vminub (vector bool char, + vector unsigned char); +vector unsigned char vec_vminub (vector unsigned char, + vector bool char); +vector unsigned char vec_vminub (vector unsigned char, + vector unsigned char); + +vector signed short vec_mladd (vector signed short, + vector signed short, + vector signed short); +vector signed short vec_mladd (vector signed short, + vector unsigned short, + vector unsigned short); +vector signed short vec_mladd (vector unsigned short, + vector signed short, + vector signed short); +vector unsigned short vec_mladd (vector unsigned short, + vector unsigned short, + vector unsigned short); + +vector signed short vec_mradds (vector signed short, + vector signed short, + vector signed short); + +vector unsigned int vec_msum (vector unsigned char, + vector unsigned char, + vector unsigned int); +vector signed int vec_msum (vector signed char, + vector unsigned char, + vector signed int); +vector unsigned int vec_msum (vector unsigned short, + vector unsigned short, + vector unsigned int); +vector signed int vec_msum (vector signed short, + vector signed short, + vector signed int); + +vector signed int vec_vmsumshm (vector signed short, + vector signed short, + vector signed int); + +vector unsigned int vec_vmsumuhm (vector unsigned short, + vector unsigned short, + vector unsigned int); + +vector signed int vec_vmsummbm (vector signed char, + vector unsigned char, + vector signed int); + +vector unsigned int vec_vmsumubm (vector unsigned char, + vector unsigned char, + vector unsigned int); + +vector unsigned int vec_msums (vector unsigned short, + vector unsigned short, + vector unsigned int); +vector signed int vec_msums (vector signed short, + vector signed short, + vector signed int); + +vector signed int vec_vmsumshs (vector signed short, + vector signed short, + vector signed int); + +vector unsigned int vec_vmsumuhs (vector unsigned short, + vector unsigned short, + vector unsigned int); + +void vec_mtvscr (vector signed int); +void vec_mtvscr (vector unsigned int); +void vec_mtvscr (vector bool int); +void vec_mtvscr (vector signed short); +void vec_mtvscr (vector unsigned short); +void vec_mtvscr (vector bool short); +void vec_mtvscr (vector pixel); +void vec_mtvscr (vector signed char); +void vec_mtvscr (vector unsigned char); +void vec_mtvscr (vector bool char); + +vector unsigned short vec_mule (vector unsigned char, + vector unsigned char); +vector signed short vec_mule (vector signed char, + vector signed char); +vector unsigned int vec_mule (vector unsigned short, + vector unsigned short); +vector signed int vec_mule (vector signed short, vector signed short); + +vector signed int vec_vmulesh (vector signed short, + vector signed short); + +vector unsigned int vec_vmuleuh (vector unsigned short, + vector unsigned short); + +vector signed short vec_vmulesb (vector signed char, + vector signed char); + +vector unsigned short vec_vmuleub (vector unsigned char, + vector unsigned char); + +vector unsigned short vec_mulo (vector unsigned char, + vector unsigned char); +vector signed short vec_mulo (vector signed char, vector signed char); +vector unsigned int vec_mulo (vector unsigned short, + vector unsigned short); +vector signed int vec_mulo (vector signed short, vector signed short); + +vector signed int vec_vmulosh (vector signed short, + vector signed short); + +vector unsigned int vec_vmulouh (vector unsigned short, + vector unsigned short); + +vector signed short vec_vmulosb (vector signed char, + vector signed char); + +vector unsigned short vec_vmuloub (vector unsigned char, + vector unsigned char); + +vector float vec_nmsub (vector float, vector float, vector float); + +vector float vec_nor (vector float, vector float); +vector signed int vec_nor (vector signed int, vector signed int); +vector unsigned int vec_nor (vector unsigned int, vector unsigned int); +vector bool int vec_nor (vector bool int, vector bool int); +vector signed short vec_nor (vector signed short, vector signed short); +vector unsigned short vec_nor (vector unsigned short, + vector unsigned short); +vector bool short vec_nor (vector bool short, vector bool short); +vector signed char vec_nor (vector signed char, vector signed char); +vector unsigned char vec_nor (vector unsigned char, + vector unsigned char); +vector bool char vec_nor (vector bool char, vector bool char); + +vector float vec_or (vector float, vector float); +vector float vec_or (vector float, vector bool int); +vector float vec_or (vector bool int, vector float); +vector bool int vec_or (vector bool int, vector bool int); +vector signed int vec_or (vector bool int, vector signed int); +vector signed int vec_or (vector signed int, vector bool int); +vector signed int vec_or (vector signed int, vector signed int); +vector unsigned int vec_or (vector bool int, vector unsigned int); +vector unsigned int vec_or (vector unsigned int, vector bool int); +vector unsigned int vec_or (vector unsigned int, vector unsigned int); +vector bool short vec_or (vector bool short, vector bool short); +vector signed short vec_or (vector bool short, vector signed short); +vector signed short vec_or (vector signed short, vector bool short); +vector signed short vec_or (vector signed short, vector signed short); +vector unsigned short vec_or (vector bool short, vector unsigned short); +vector unsigned short vec_or (vector unsigned short, vector bool short); +vector unsigned short vec_or (vector unsigned short, + vector unsigned short); +vector signed char vec_or (vector bool char, vector signed char); +vector bool char vec_or (vector bool char, vector bool char); +vector signed char vec_or (vector signed char, vector bool char); +vector signed char vec_or (vector signed char, vector signed char); +vector unsigned char vec_or (vector bool char, vector unsigned char); +vector unsigned char vec_or (vector unsigned char, vector bool char); +vector unsigned char vec_or (vector unsigned char, + vector unsigned char); + +vector signed char vec_pack (vector signed short, vector signed short); +vector unsigned char vec_pack (vector unsigned short, + vector unsigned short); +vector bool char vec_pack (vector bool short, vector bool short); +vector signed short vec_pack (vector signed int, vector signed int); +vector unsigned short vec_pack (vector unsigned int, + vector unsigned int); +vector bool short vec_pack (vector bool int, vector bool int); + +vector bool short vec_vpkuwum (vector bool int, vector bool int); +vector signed short vec_vpkuwum (vector signed int, vector signed int); +vector unsigned short vec_vpkuwum (vector unsigned int, + vector unsigned int); + +vector bool char vec_vpkuhum (vector bool short, vector bool short); +vector signed char vec_vpkuhum (vector signed short, + vector signed short); +vector unsigned char vec_vpkuhum (vector unsigned short, + vector unsigned short); + +vector pixel vec_packpx (vector unsigned int, vector unsigned int); + +vector unsigned char vec_packs (vector unsigned short, + vector unsigned short); +vector signed char vec_packs (vector signed short, vector signed short); +vector unsigned short vec_packs (vector unsigned int, + vector unsigned int); +vector signed short vec_packs (vector signed int, vector signed int); + +vector signed short vec_vpkswss (vector signed int, vector signed int); + +vector unsigned short vec_vpkuwus (vector unsigned int, + vector unsigned int); + +vector signed char vec_vpkshss (vector signed short, + vector signed short); + +vector unsigned char vec_vpkuhus (vector unsigned short, + vector unsigned short); + +vector unsigned char vec_packsu (vector unsigned short, + vector unsigned short); +vector unsigned char vec_packsu (vector signed short, + vector signed short); +vector unsigned short vec_packsu (vector unsigned int, + vector unsigned int); +vector unsigned short vec_packsu (vector signed int, vector signed int); + +vector unsigned short vec_vpkswus (vector signed int, + vector signed int); + +vector unsigned char vec_vpkshus (vector signed short, + vector signed short); + +vector float vec_perm (vector float, + vector float, + vector unsigned char); +vector signed int vec_perm (vector signed int, + vector signed int, + vector unsigned char); +vector unsigned int vec_perm (vector unsigned int, + vector unsigned int, + vector unsigned char); +vector bool int vec_perm (vector bool int, + vector bool int, + vector unsigned char); +vector signed short vec_perm (vector signed short, + vector signed short, + vector unsigned char); +vector unsigned short vec_perm (vector unsigned short, + vector unsigned short, + vector unsigned char); +vector bool short vec_perm (vector bool short, + vector bool short, + vector unsigned char); +vector pixel vec_perm (vector pixel, + vector pixel, + vector unsigned char); +vector signed char vec_perm (vector signed char, + vector signed char, + vector unsigned char); +vector unsigned char vec_perm (vector unsigned char, + vector unsigned char, + vector unsigned char); +vector bool char vec_perm (vector bool char, + vector bool char, + vector unsigned char); + +vector float vec_re (vector float); + +vector signed char vec_rl (vector signed char, + vector unsigned char); +vector unsigned char vec_rl (vector unsigned char, + vector unsigned char); +vector signed short vec_rl (vector signed short, vector unsigned short); +vector unsigned short vec_rl (vector unsigned short, + vector unsigned short); +vector signed int vec_rl (vector signed int, vector unsigned int); +vector unsigned int vec_rl (vector unsigned int, vector unsigned int); + +vector signed int vec_vrlw (vector signed int, vector unsigned int); +vector unsigned int vec_vrlw (vector unsigned int, vector unsigned int); + +vector signed short vec_vrlh (vector signed short, + vector unsigned short); +vector unsigned short vec_vrlh (vector unsigned short, + vector unsigned short); + +vector signed char vec_vrlb (vector signed char, vector unsigned char); +vector unsigned char vec_vrlb (vector unsigned char, + vector unsigned char); + +vector float vec_round (vector float); + +vector float vec_recip (vector float, vector float); + +vector float vec_rsqrt (vector float); + +vector float vec_rsqrte (vector float); + +vector float vec_sel (vector float, vector float, vector bool int); +vector float vec_sel (vector float, vector float, vector unsigned int); +vector signed int vec_sel (vector signed int, + vector signed int, + vector bool int); +vector signed int vec_sel (vector signed int, + vector signed int, + vector unsigned int); +vector unsigned int vec_sel (vector unsigned int, + vector unsigned int, + vector bool int); +vector unsigned int vec_sel (vector unsigned int, + vector unsigned int, + vector unsigned int); +vector bool int vec_sel (vector bool int, + vector bool int, + vector bool int); +vector bool int vec_sel (vector bool int, + vector bool int, + vector unsigned int); +vector signed short vec_sel (vector signed short, + vector signed short, + vector bool short); +vector signed short vec_sel (vector signed short, + vector signed short, + vector unsigned short); +vector unsigned short vec_sel (vector unsigned short, + vector unsigned short, + vector bool short); +vector unsigned short vec_sel (vector unsigned short, + vector unsigned short, + vector unsigned short); +vector bool short vec_sel (vector bool short, + vector bool short, + vector bool short); +vector bool short vec_sel (vector bool short, + vector bool short, + vector unsigned short); +vector signed char vec_sel (vector signed char, + vector signed char, + vector bool char); +vector signed char vec_sel (vector signed char, + vector signed char, + vector unsigned char); +vector unsigned char vec_sel (vector unsigned char, + vector unsigned char, + vector bool char); +vector unsigned char vec_sel (vector unsigned char, + vector unsigned char, + vector unsigned char); +vector bool char vec_sel (vector bool char, + vector bool char, + vector bool char); +vector bool char vec_sel (vector bool char, + vector bool char, + vector unsigned char); + +vector signed char vec_sl (vector signed char, + vector unsigned char); +vector unsigned char vec_sl (vector unsigned char, + vector unsigned char); +vector signed short vec_sl (vector signed short, vector unsigned short); +vector unsigned short vec_sl (vector unsigned short, + vector unsigned short); +vector signed int vec_sl (vector signed int, vector unsigned int); +vector unsigned int vec_sl (vector unsigned int, vector unsigned int); + +vector signed int vec_vslw (vector signed int, vector unsigned int); +vector unsigned int vec_vslw (vector unsigned int, vector unsigned int); + +vector signed short vec_vslh (vector signed short, + vector unsigned short); +vector unsigned short vec_vslh (vector unsigned short, + vector unsigned short); + +vector signed char vec_vslb (vector signed char, vector unsigned char); +vector unsigned char vec_vslb (vector unsigned char, + vector unsigned char); + +vector float vec_sld (vector float, vector float, const int); +vector signed int vec_sld (vector signed int, + vector signed int, + const int); +vector unsigned int vec_sld (vector unsigned int, + vector unsigned int, + const int); +vector bool int vec_sld (vector bool int, + vector bool int, + const int); +vector signed short vec_sld (vector signed short, + vector signed short, + const int); +vector unsigned short vec_sld (vector unsigned short, + vector unsigned short, + const int); +vector bool short vec_sld (vector bool short, + vector bool short, + const int); +vector pixel vec_sld (vector pixel, + vector pixel, + const int); +vector signed char vec_sld (vector signed char, + vector signed char, + const int); +vector unsigned char vec_sld (vector unsigned char, + vector unsigned char, + const int); +vector bool char vec_sld (vector bool char, + vector bool char, + const int); + +vector signed int vec_sll (vector signed int, + vector unsigned int); +vector signed int vec_sll (vector signed int, + vector unsigned short); +vector signed int vec_sll (vector signed int, + vector unsigned char); +vector unsigned int vec_sll (vector unsigned int, + vector unsigned int); +vector unsigned int vec_sll (vector unsigned int, + vector unsigned short); +vector unsigned int vec_sll (vector unsigned int, + vector unsigned char); +vector bool int vec_sll (vector bool int, + vector unsigned int); +vector bool int vec_sll (vector bool int, + vector unsigned short); +vector bool int vec_sll (vector bool int, + vector unsigned char); +vector signed short vec_sll (vector signed short, + vector unsigned int); +vector signed short vec_sll (vector signed short, + vector unsigned short); +vector signed short vec_sll (vector signed short, + vector unsigned char); +vector unsigned short vec_sll (vector unsigned short, + vector unsigned int); +vector unsigned short vec_sll (vector unsigned short, + vector unsigned short); +vector unsigned short vec_sll (vector unsigned short, + vector unsigned char); +vector bool short vec_sll (vector bool short, vector unsigned int); +vector bool short vec_sll (vector bool short, vector unsigned short); +vector bool short vec_sll (vector bool short, vector unsigned char); +vector pixel vec_sll (vector pixel, vector unsigned int); +vector pixel vec_sll (vector pixel, vector unsigned short); +vector pixel vec_sll (vector pixel, vector unsigned char); +vector signed char vec_sll (vector signed char, vector unsigned int); +vector signed char vec_sll (vector signed char, vector unsigned short); +vector signed char vec_sll (vector signed char, vector unsigned char); +vector unsigned char vec_sll (vector unsigned char, + vector unsigned int); +vector unsigned char vec_sll (vector unsigned char, + vector unsigned short); +vector unsigned char vec_sll (vector unsigned char, + vector unsigned char); +vector bool char vec_sll (vector bool char, vector unsigned int); +vector bool char vec_sll (vector bool char, vector unsigned short); +vector bool char vec_sll (vector bool char, vector unsigned char); + +vector float vec_slo (vector float, vector signed char); +vector float vec_slo (vector float, vector unsigned char); +vector signed int vec_slo (vector signed int, vector signed char); +vector signed int vec_slo (vector signed int, vector unsigned char); +vector unsigned int vec_slo (vector unsigned int, vector signed char); +vector unsigned int vec_slo (vector unsigned int, vector unsigned char); +vector signed short vec_slo (vector signed short, vector signed char); +vector signed short vec_slo (vector signed short, vector unsigned char); +vector unsigned short vec_slo (vector unsigned short, + vector signed char); +vector unsigned short vec_slo (vector unsigned short, + vector unsigned char); +vector pixel vec_slo (vector pixel, vector signed char); +vector pixel vec_slo (vector pixel, vector unsigned char); +vector signed char vec_slo (vector signed char, vector signed char); +vector signed char vec_slo (vector signed char, vector unsigned char); +vector unsigned char vec_slo (vector unsigned char, vector signed char); +vector unsigned char vec_slo (vector unsigned char, + vector unsigned char); + +vector signed char vec_splat (vector signed char, const int); +vector unsigned char vec_splat (vector unsigned char, const int); +vector bool char vec_splat (vector bool char, const int); +vector signed short vec_splat (vector signed short, const int); +vector unsigned short vec_splat (vector unsigned short, const int); +vector bool short vec_splat (vector bool short, const int); +vector pixel vec_splat (vector pixel, const int); +vector float vec_splat (vector float, const int); +vector signed int vec_splat (vector signed int, const int); +vector unsigned int vec_splat (vector unsigned int, const int); +vector bool int vec_splat (vector bool int, const int); + +vector float vec_vspltw (vector float, const int); +vector signed int vec_vspltw (vector signed int, const int); +vector unsigned int vec_vspltw (vector unsigned int, const int); +vector bool int vec_vspltw (vector bool int, const int); + +vector bool short vec_vsplth (vector bool short, const int); +vector signed short vec_vsplth (vector signed short, const int); +vector unsigned short vec_vsplth (vector unsigned short, const int); +vector pixel vec_vsplth (vector pixel, const int); + +vector signed char vec_vspltb (vector signed char, const int); +vector unsigned char vec_vspltb (vector unsigned char, const int); +vector bool char vec_vspltb (vector bool char, const int); + +vector signed char vec_splat_s8 (const int); + +vector signed short vec_splat_s16 (const int); + +vector signed int vec_splat_s32 (const int); + +vector unsigned char vec_splat_u8 (const int); + +vector unsigned short vec_splat_u16 (const int); + +vector unsigned int vec_splat_u32 (const int); + +vector signed char vec_sr (vector signed char, vector unsigned char); +vector unsigned char vec_sr (vector unsigned char, + vector unsigned char); +vector signed short vec_sr (vector signed short, + vector unsigned short); +vector unsigned short vec_sr (vector unsigned short, + vector unsigned short); +vector signed int vec_sr (vector signed int, vector unsigned int); +vector unsigned int vec_sr (vector unsigned int, vector unsigned int); + +vector signed int vec_vsrw (vector signed int, vector unsigned int); +vector unsigned int vec_vsrw (vector unsigned int, vector unsigned int); + +vector signed short vec_vsrh (vector signed short, + vector unsigned short); +vector unsigned short vec_vsrh (vector unsigned short, + vector unsigned short); + +vector signed char vec_vsrb (vector signed char, vector unsigned char); +vector unsigned char vec_vsrb (vector unsigned char, + vector unsigned char); + +vector signed char vec_sra (vector signed char, vector unsigned char); +vector unsigned char vec_sra (vector unsigned char, + vector unsigned char); +vector signed short vec_sra (vector signed short, + vector unsigned short); +vector unsigned short vec_sra (vector unsigned short, + vector unsigned short); +vector signed int vec_sra (vector signed int, vector unsigned int); +vector unsigned int vec_sra (vector unsigned int, vector unsigned int); + +vector signed int vec_vsraw (vector signed int, vector unsigned int); +vector unsigned int vec_vsraw (vector unsigned int, + vector unsigned int); + +vector signed short vec_vsrah (vector signed short, + vector unsigned short); +vector unsigned short vec_vsrah (vector unsigned short, + vector unsigned short); + +vector signed char vec_vsrab (vector signed char, vector unsigned char); +vector unsigned char vec_vsrab (vector unsigned char, + vector unsigned char); + +vector signed int vec_srl (vector signed int, vector unsigned int); +vector signed int vec_srl (vector signed int, vector unsigned short); +vector signed int vec_srl (vector signed int, vector unsigned char); +vector unsigned int vec_srl (vector unsigned int, vector unsigned int); +vector unsigned int vec_srl (vector unsigned int, + vector unsigned short); +vector unsigned int vec_srl (vector unsigned int, vector unsigned char); +vector bool int vec_srl (vector bool int, vector unsigned int); +vector bool int vec_srl (vector bool int, vector unsigned short); +vector bool int vec_srl (vector bool int, vector unsigned char); +vector signed short vec_srl (vector signed short, vector unsigned int); +vector signed short vec_srl (vector signed short, + vector unsigned short); +vector signed short vec_srl (vector signed short, vector unsigned char); +vector unsigned short vec_srl (vector unsigned short, + vector unsigned int); +vector unsigned short vec_srl (vector unsigned short, + vector unsigned short); +vector unsigned short vec_srl (vector unsigned short, + vector unsigned char); +vector bool short vec_srl (vector bool short, vector unsigned int); +vector bool short vec_srl (vector bool short, vector unsigned short); +vector bool short vec_srl (vector bool short, vector unsigned char); +vector pixel vec_srl (vector pixel, vector unsigned int); +vector pixel vec_srl (vector pixel, vector unsigned short); +vector pixel vec_srl (vector pixel, vector unsigned char); +vector signed char vec_srl (vector signed char, vector unsigned int); +vector signed char vec_srl (vector signed char, vector unsigned short); +vector signed char vec_srl (vector signed char, vector unsigned char); +vector unsigned char vec_srl (vector unsigned char, + vector unsigned int); +vector unsigned char vec_srl (vector unsigned char, + vector unsigned short); +vector unsigned char vec_srl (vector unsigned char, + vector unsigned char); +vector bool char vec_srl (vector bool char, vector unsigned int); +vector bool char vec_srl (vector bool char, vector unsigned short); +vector bool char vec_srl (vector bool char, vector unsigned char); + +vector float vec_sro (vector float, vector signed char); +vector float vec_sro (vector float, vector unsigned char); +vector signed int vec_sro (vector signed int, vector signed char); +vector signed int vec_sro (vector signed int, vector unsigned char); +vector unsigned int vec_sro (vector unsigned int, vector signed char); +vector unsigned int vec_sro (vector unsigned int, vector unsigned char); +vector signed short vec_sro (vector signed short, vector signed char); +vector signed short vec_sro (vector signed short, vector unsigned char); +vector unsigned short vec_sro (vector unsigned short, + vector signed char); +vector unsigned short vec_sro (vector unsigned short, + vector unsigned char); +vector pixel vec_sro (vector pixel, vector signed char); +vector pixel vec_sro (vector pixel, vector unsigned char); +vector signed char vec_sro (vector signed char, vector signed char); +vector signed char vec_sro (vector signed char, vector unsigned char); +vector unsigned char vec_sro (vector unsigned char, vector signed char); +vector unsigned char vec_sro (vector unsigned char, + vector unsigned char); + +void vec_st (vector float, int, vector float *); +void vec_st (vector float, int, float *); +void vec_st (vector signed int, int, vector signed int *); +void vec_st (vector signed int, int, int *); +void vec_st (vector unsigned int, int, vector unsigned int *); +void vec_st (vector unsigned int, int, unsigned int *); +void vec_st (vector bool int, int, vector bool int *); +void vec_st (vector bool int, int, unsigned int *); +void vec_st (vector bool int, int, int *); +void vec_st (vector signed short, int, vector signed short *); +void vec_st (vector signed short, int, short *); +void vec_st (vector unsigned short, int, vector unsigned short *); +void vec_st (vector unsigned short, int, unsigned short *); +void vec_st (vector bool short, int, vector bool short *); +void vec_st (vector bool short, int, unsigned short *); +void vec_st (vector pixel, int, vector pixel *); +void vec_st (vector pixel, int, unsigned short *); +void vec_st (vector pixel, int, short *); +void vec_st (vector bool short, int, short *); +void vec_st (vector signed char, int, vector signed char *); +void vec_st (vector signed char, int, signed char *); +void vec_st (vector unsigned char, int, vector unsigned char *); +void vec_st (vector unsigned char, int, unsigned char *); +void vec_st (vector bool char, int, vector bool char *); +void vec_st (vector bool char, int, unsigned char *); +void vec_st (vector bool char, int, signed char *); + +void vec_ste (vector signed char, int, signed char *); +void vec_ste (vector unsigned char, int, unsigned char *); +void vec_ste (vector bool char, int, signed char *); +void vec_ste (vector bool char, int, unsigned char *); +void vec_ste (vector signed short, int, short *); +void vec_ste (vector unsigned short, int, unsigned short *); +void vec_ste (vector bool short, int, short *); +void vec_ste (vector bool short, int, unsigned short *); +void vec_ste (vector pixel, int, short *); +void vec_ste (vector pixel, int, unsigned short *); +void vec_ste (vector float, int, float *); +void vec_ste (vector signed int, int, int *); +void vec_ste (vector unsigned int, int, unsigned int *); +void vec_ste (vector bool int, int, int *); +void vec_ste (vector bool int, int, unsigned int *); + +void vec_stvewx (vector float, int, float *); +void vec_stvewx (vector signed int, int, int *); +void vec_stvewx (vector unsigned int, int, unsigned int *); +void vec_stvewx (vector bool int, int, int *); +void vec_stvewx (vector bool int, int, unsigned int *); + +void vec_stvehx (vector signed short, int, short *); +void vec_stvehx (vector unsigned short, int, unsigned short *); +void vec_stvehx (vector bool short, int, short *); +void vec_stvehx (vector bool short, int, unsigned short *); +void vec_stvehx (vector pixel, int, short *); +void vec_stvehx (vector pixel, int, unsigned short *); + +void vec_stvebx (vector signed char, int, signed char *); +void vec_stvebx (vector unsigned char, int, unsigned char *); +void vec_stvebx (vector bool char, int, signed char *); +void vec_stvebx (vector bool char, int, unsigned char *); + +void vec_stl (vector float, int, vector float *); +void vec_stl (vector float, int, float *); +void vec_stl (vector signed int, int, vector signed int *); +void vec_stl (vector signed int, int, int *); +void vec_stl (vector unsigned int, int, vector unsigned int *); +void vec_stl (vector unsigned int, int, unsigned int *); +void vec_stl (vector bool int, int, vector bool int *); +void vec_stl (vector bool int, int, unsigned int *); +void vec_stl (vector bool int, int, int *); +void vec_stl (vector signed short, int, vector signed short *); +void vec_stl (vector signed short, int, short *); +void vec_stl (vector unsigned short, int, vector unsigned short *); +void vec_stl (vector unsigned short, int, unsigned short *); +void vec_stl (vector bool short, int, vector bool short *); +void vec_stl (vector bool short, int, unsigned short *); +void vec_stl (vector bool short, int, short *); +void vec_stl (vector pixel, int, vector pixel *); +void vec_stl (vector pixel, int, unsigned short *); +void vec_stl (vector pixel, int, short *); +void vec_stl (vector signed char, int, vector signed char *); +void vec_stl (vector signed char, int, signed char *); +void vec_stl (vector unsigned char, int, vector unsigned char *); +void vec_stl (vector unsigned char, int, unsigned char *); +void vec_stl (vector bool char, int, vector bool char *); +void vec_stl (vector bool char, int, unsigned char *); +void vec_stl (vector bool char, int, signed char *); + +vector signed char vec_sub (vector bool char, vector signed char); +vector signed char vec_sub (vector signed char, vector bool char); +vector signed char vec_sub (vector signed char, vector signed char); +vector unsigned char vec_sub (vector bool char, vector unsigned char); +vector unsigned char vec_sub (vector unsigned char, vector bool char); +vector unsigned char vec_sub (vector unsigned char, + vector unsigned char); +vector signed short vec_sub (vector bool short, vector signed short); +vector signed short vec_sub (vector signed short, vector bool short); +vector signed short vec_sub (vector signed short, vector signed short); +vector unsigned short vec_sub (vector bool short, + vector unsigned short); +vector unsigned short vec_sub (vector unsigned short, + vector bool short); +vector unsigned short vec_sub (vector unsigned short, + vector unsigned short); +vector signed int vec_sub (vector bool int, vector signed int); +vector signed int vec_sub (vector signed int, vector bool int); +vector signed int vec_sub (vector signed int, vector signed int); +vector unsigned int vec_sub (vector bool int, vector unsigned int); +vector unsigned int vec_sub (vector unsigned int, vector bool int); +vector unsigned int vec_sub (vector unsigned int, vector unsigned int); +vector float vec_sub (vector float, vector float); + +vector float vec_vsubfp (vector float, vector float); + +vector signed int vec_vsubuwm (vector bool int, vector signed int); +vector signed int vec_vsubuwm (vector signed int, vector bool int); +vector signed int vec_vsubuwm (vector signed int, vector signed int); +vector unsigned int vec_vsubuwm (vector bool int, vector unsigned int); +vector unsigned int vec_vsubuwm (vector unsigned int, vector bool int); +vector unsigned int vec_vsubuwm (vector unsigned int, + vector unsigned int); + +vector signed short vec_vsubuhm (vector bool short, + vector signed short); +vector signed short vec_vsubuhm (vector signed short, + vector bool short); +vector signed short vec_vsubuhm (vector signed short, + vector signed short); +vector unsigned short vec_vsubuhm (vector bool short, + vector unsigned short); +vector unsigned short vec_vsubuhm (vector unsigned short, + vector bool short); +vector unsigned short vec_vsubuhm (vector unsigned short, + vector unsigned short); + +vector signed char vec_vsububm (vector bool char, vector signed char); +vector signed char vec_vsububm (vector signed char, vector bool char); +vector signed char vec_vsububm (vector signed char, vector signed char); +vector unsigned char vec_vsububm (vector bool char, + vector unsigned char); +vector unsigned char vec_vsububm (vector unsigned char, + vector bool char); +vector unsigned char vec_vsububm (vector unsigned char, + vector unsigned char); + +vector unsigned int vec_subc (vector unsigned int, vector unsigned int); + +vector unsigned char vec_subs (vector bool char, vector unsigned char); +vector unsigned char vec_subs (vector unsigned char, vector bool char); +vector unsigned char vec_subs (vector unsigned char, + vector unsigned char); +vector signed char vec_subs (vector bool char, vector signed char); +vector signed char vec_subs (vector signed char, vector bool char); +vector signed char vec_subs (vector signed char, vector signed char); +vector unsigned short vec_subs (vector bool short, + vector unsigned short); +vector unsigned short vec_subs (vector unsigned short, + vector bool short); +vector unsigned short vec_subs (vector unsigned short, + vector unsigned short); +vector signed short vec_subs (vector bool short, vector signed short); +vector signed short vec_subs (vector signed short, vector bool short); +vector signed short vec_subs (vector signed short, vector signed short); +vector unsigned int vec_subs (vector bool int, vector unsigned int); +vector unsigned int vec_subs (vector unsigned int, vector bool int); +vector unsigned int vec_subs (vector unsigned int, vector unsigned int); +vector signed int vec_subs (vector bool int, vector signed int); +vector signed int vec_subs (vector signed int, vector bool int); +vector signed int vec_subs (vector signed int, vector signed int); + +vector signed int vec_vsubsws (vector bool int, vector signed int); +vector signed int vec_vsubsws (vector signed int, vector bool int); +vector signed int vec_vsubsws (vector signed int, vector signed int); + +vector unsigned int vec_vsubuws (vector bool int, vector unsigned int); +vector unsigned int vec_vsubuws (vector unsigned int, vector bool int); +vector unsigned int vec_vsubuws (vector unsigned int, + vector unsigned int); + +vector signed short vec_vsubshs (vector bool short, + vector signed short); +vector signed short vec_vsubshs (vector signed short, + vector bool short); +vector signed short vec_vsubshs (vector signed short, + vector signed short); + +vector unsigned short vec_vsubuhs (vector bool short, + vector unsigned short); +vector unsigned short vec_vsubuhs (vector unsigned short, + vector bool short); +vector unsigned short vec_vsubuhs (vector unsigned short, + vector unsigned short); + +vector signed char vec_vsubsbs (vector bool char, vector signed char); +vector signed char vec_vsubsbs (vector signed char, vector bool char); +vector signed char vec_vsubsbs (vector signed char, vector signed char); + +vector unsigned char vec_vsububs (vector bool char, + vector unsigned char); +vector unsigned char vec_vsububs (vector unsigned char, + vector bool char); +vector unsigned char vec_vsububs (vector unsigned char, + vector unsigned char); + +vector unsigned int vec_sum4s (vector unsigned char, + vector unsigned int); +vector signed int vec_sum4s (vector signed char, vector signed int); +vector signed int vec_sum4s (vector signed short, vector signed int); + +vector signed int vec_vsum4shs (vector signed short, vector signed int); + +vector signed int vec_vsum4sbs (vector signed char, vector signed int); + +vector unsigned int vec_vsum4ubs (vector unsigned char, + vector unsigned int); + +vector signed int vec_sum2s (vector signed int, vector signed int); + +vector signed int vec_sums (vector signed int, vector signed int); + +vector float vec_trunc (vector float); + +vector signed short vec_unpackh (vector signed char); +vector bool short vec_unpackh (vector bool char); +vector signed int vec_unpackh (vector signed short); +vector bool int vec_unpackh (vector bool short); +vector unsigned int vec_unpackh (vector pixel); + +vector bool int vec_vupkhsh (vector bool short); +vector signed int vec_vupkhsh (vector signed short); + +vector unsigned int vec_vupkhpx (vector pixel); + +vector bool short vec_vupkhsb (vector bool char); +vector signed short vec_vupkhsb (vector signed char); + +vector signed short vec_unpackl (vector signed char); +vector bool short vec_unpackl (vector bool char); +vector unsigned int vec_unpackl (vector pixel); +vector signed int vec_unpackl (vector signed short); +vector bool int vec_unpackl (vector bool short); + +vector unsigned int vec_vupklpx (vector pixel); + +vector bool int vec_vupklsh (vector bool short); +vector signed int vec_vupklsh (vector signed short); + +vector bool short vec_vupklsb (vector bool char); +vector signed short vec_vupklsb (vector signed char); + +vector float vec_xor (vector float, vector float); +vector float vec_xor (vector float, vector bool int); +vector float vec_xor (vector bool int, vector float); +vector bool int vec_xor (vector bool int, vector bool int); +vector signed int vec_xor (vector bool int, vector signed int); +vector signed int vec_xor (vector signed int, vector bool int); +vector signed int vec_xor (vector signed int, vector signed int); +vector unsigned int vec_xor (vector bool int, vector unsigned int); +vector unsigned int vec_xor (vector unsigned int, vector bool int); +vector unsigned int vec_xor (vector unsigned int, vector unsigned int); +vector bool short vec_xor (vector bool short, vector bool short); +vector signed short vec_xor (vector bool short, vector signed short); +vector signed short vec_xor (vector signed short, vector bool short); +vector signed short vec_xor (vector signed short, vector signed short); +vector unsigned short vec_xor (vector bool short, + vector unsigned short); +vector unsigned short vec_xor (vector unsigned short, + vector bool short); +vector unsigned short vec_xor (vector unsigned short, + vector unsigned short); +vector signed char vec_xor (vector bool char, vector signed char); +vector bool char vec_xor (vector bool char, vector bool char); +vector signed char vec_xor (vector signed char, vector bool char); +vector signed char vec_xor (vector signed char, vector signed char); +vector unsigned char vec_xor (vector bool char, vector unsigned char); +vector unsigned char vec_xor (vector unsigned char, vector bool char); +vector unsigned char vec_xor (vector unsigned char, + vector unsigned char); + +int vec_all_eq (vector signed char, vector bool char); +int vec_all_eq (vector signed char, vector signed char); +int vec_all_eq (vector unsigned char, vector bool char); +int vec_all_eq (vector unsigned char, vector unsigned char); +int vec_all_eq (vector bool char, vector bool char); +int vec_all_eq (vector bool char, vector unsigned char); +int vec_all_eq (vector bool char, vector signed char); +int vec_all_eq (vector signed short, vector bool short); +int vec_all_eq (vector signed short, vector signed short); +int vec_all_eq (vector unsigned short, vector bool short); +int vec_all_eq (vector unsigned short, vector unsigned short); +int vec_all_eq (vector bool short, vector bool short); +int vec_all_eq (vector bool short, vector unsigned short); +int vec_all_eq (vector bool short, vector signed short); +int vec_all_eq (vector pixel, vector pixel); +int vec_all_eq (vector signed int, vector bool int); +int vec_all_eq (vector signed int, vector signed int); +int vec_all_eq (vector unsigned int, vector bool int); +int vec_all_eq (vector unsigned int, vector unsigned int); +int vec_all_eq (vector bool int, vector bool int); +int vec_all_eq (vector bool int, vector unsigned int); +int vec_all_eq (vector bool int, vector signed int); +int vec_all_eq (vector float, vector float); + +int vec_all_ge (vector bool char, vector unsigned char); +int vec_all_ge (vector unsigned char, vector bool char); +int vec_all_ge (vector unsigned char, vector unsigned char); +int vec_all_ge (vector bool char, vector signed char); +int vec_all_ge (vector signed char, vector bool char); +int vec_all_ge (vector signed char, vector signed char); +int vec_all_ge (vector bool short, vector unsigned short); +int vec_all_ge (vector unsigned short, vector bool short); +int vec_all_ge (vector unsigned short, vector unsigned short); +int vec_all_ge (vector signed short, vector signed short); +int vec_all_ge (vector bool short, vector signed short); +int vec_all_ge (vector signed short, vector bool short); +int vec_all_ge (vector bool int, vector unsigned int); +int vec_all_ge (vector unsigned int, vector bool int); +int vec_all_ge (vector unsigned int, vector unsigned int); +int vec_all_ge (vector bool int, vector signed int); +int vec_all_ge (vector signed int, vector bool int); +int vec_all_ge (vector signed int, vector signed int); +int vec_all_ge (vector float, vector float); + +int vec_all_gt (vector bool char, vector unsigned char); +int vec_all_gt (vector unsigned char, vector bool char); +int vec_all_gt (vector unsigned char, vector unsigned char); +int vec_all_gt (vector bool char, vector signed char); +int vec_all_gt (vector signed char, vector bool char); +int vec_all_gt (vector signed char, vector signed char); +int vec_all_gt (vector bool short, vector unsigned short); +int vec_all_gt (vector unsigned short, vector bool short); +int vec_all_gt (vector unsigned short, vector unsigned short); +int vec_all_gt (vector bool short, vector signed short); +int vec_all_gt (vector signed short, vector bool short); +int vec_all_gt (vector signed short, vector signed short); +int vec_all_gt (vector bool int, vector unsigned int); +int vec_all_gt (vector unsigned int, vector bool int); +int vec_all_gt (vector unsigned int, vector unsigned int); +int vec_all_gt (vector bool int, vector signed int); +int vec_all_gt (vector signed int, vector bool int); +int vec_all_gt (vector signed int, vector signed int); +int vec_all_gt (vector float, vector float); + +int vec_all_in (vector float, vector float); + +int vec_all_le (vector bool char, vector unsigned char); +int vec_all_le (vector unsigned char, vector bool char); +int vec_all_le (vector unsigned char, vector unsigned char); +int vec_all_le (vector bool char, vector signed char); +int vec_all_le (vector signed char, vector bool char); +int vec_all_le (vector signed char, vector signed char); +int vec_all_le (vector bool short, vector unsigned short); +int vec_all_le (vector unsigned short, vector bool short); +int vec_all_le (vector unsigned short, vector unsigned short); +int vec_all_le (vector bool short, vector signed short); +int vec_all_le (vector signed short, vector bool short); +int vec_all_le (vector signed short, vector signed short); +int vec_all_le (vector bool int, vector unsigned int); +int vec_all_le (vector unsigned int, vector bool int); +int vec_all_le (vector unsigned int, vector unsigned int); +int vec_all_le (vector bool int, vector signed int); +int vec_all_le (vector signed int, vector bool int); +int vec_all_le (vector signed int, vector signed int); +int vec_all_le (vector float, vector float); + +int vec_all_lt (vector bool char, vector unsigned char); +int vec_all_lt (vector unsigned char, vector bool char); +int vec_all_lt (vector unsigned char, vector unsigned char); +int vec_all_lt (vector bool char, vector signed char); +int vec_all_lt (vector signed char, vector bool char); +int vec_all_lt (vector signed char, vector signed char); +int vec_all_lt (vector bool short, vector unsigned short); +int vec_all_lt (vector unsigned short, vector bool short); +int vec_all_lt (vector unsigned short, vector unsigned short); +int vec_all_lt (vector bool short, vector signed short); +int vec_all_lt (vector signed short, vector bool short); +int vec_all_lt (vector signed short, vector signed short); +int vec_all_lt (vector bool int, vector unsigned int); +int vec_all_lt (vector unsigned int, vector bool int); +int vec_all_lt (vector unsigned int, vector unsigned int); +int vec_all_lt (vector bool int, vector signed int); +int vec_all_lt (vector signed int, vector bool int); +int vec_all_lt (vector signed int, vector signed int); +int vec_all_lt (vector float, vector float); + +int vec_all_nan (vector float); + +int vec_all_ne (vector signed char, vector bool char); +int vec_all_ne (vector signed char, vector signed char); +int vec_all_ne (vector unsigned char, vector bool char); +int vec_all_ne (vector unsigned char, vector unsigned char); +int vec_all_ne (vector bool char, vector bool char); +int vec_all_ne (vector bool char, vector unsigned char); +int vec_all_ne (vector bool char, vector signed char); +int vec_all_ne (vector signed short, vector bool short); +int vec_all_ne (vector signed short, vector signed short); +int vec_all_ne (vector unsigned short, vector bool short); +int vec_all_ne (vector unsigned short, vector unsigned short); +int vec_all_ne (vector bool short, vector bool short); +int vec_all_ne (vector bool short, vector unsigned short); +int vec_all_ne (vector bool short, vector signed short); +int vec_all_ne (vector pixel, vector pixel); +int vec_all_ne (vector signed int, vector bool int); +int vec_all_ne (vector signed int, vector signed int); +int vec_all_ne (vector unsigned int, vector bool int); +int vec_all_ne (vector unsigned int, vector unsigned int); +int vec_all_ne (vector bool int, vector bool int); +int vec_all_ne (vector bool int, vector unsigned int); +int vec_all_ne (vector bool int, vector signed int); +int vec_all_ne (vector float, vector float); + +int vec_all_nge (vector float, vector float); + +int vec_all_ngt (vector float, vector float); + +int vec_all_nle (vector float, vector float); + +int vec_all_nlt (vector float, vector float); + +int vec_all_numeric (vector float); + +int vec_any_eq (vector signed char, vector bool char); +int vec_any_eq (vector signed char, vector signed char); +int vec_any_eq (vector unsigned char, vector bool char); +int vec_any_eq (vector unsigned char, vector unsigned char); +int vec_any_eq (vector bool char, vector bool char); +int vec_any_eq (vector bool char, vector unsigned char); +int vec_any_eq (vector bool char, vector signed char); +int vec_any_eq (vector signed short, vector bool short); +int vec_any_eq (vector signed short, vector signed short); +int vec_any_eq (vector unsigned short, vector bool short); +int vec_any_eq (vector unsigned short, vector unsigned short); +int vec_any_eq (vector bool short, vector bool short); +int vec_any_eq (vector bool short, vector unsigned short); +int vec_any_eq (vector bool short, vector signed short); +int vec_any_eq (vector pixel, vector pixel); +int vec_any_eq (vector signed int, vector bool int); +int vec_any_eq (vector signed int, vector signed int); +int vec_any_eq (vector unsigned int, vector bool int); +int vec_any_eq (vector unsigned int, vector unsigned int); +int vec_any_eq (vector bool int, vector bool int); +int vec_any_eq (vector bool int, vector unsigned int); +int vec_any_eq (vector bool int, vector signed int); +int vec_any_eq (vector float, vector float); + +int vec_any_ge (vector signed char, vector bool char); +int vec_any_ge (vector unsigned char, vector bool char); +int vec_any_ge (vector unsigned char, vector unsigned char); +int vec_any_ge (vector signed char, vector signed char); +int vec_any_ge (vector bool char, vector unsigned char); +int vec_any_ge (vector bool char, vector signed char); +int vec_any_ge (vector unsigned short, vector bool short); +int vec_any_ge (vector unsigned short, vector unsigned short); +int vec_any_ge (vector signed short, vector signed short); +int vec_any_ge (vector signed short, vector bool short); +int vec_any_ge (vector bool short, vector unsigned short); +int vec_any_ge (vector bool short, vector signed short); +int vec_any_ge (vector signed int, vector bool int); +int vec_any_ge (vector unsigned int, vector bool int); +int vec_any_ge (vector unsigned int, vector unsigned int); +int vec_any_ge (vector signed int, vector signed int); +int vec_any_ge (vector bool int, vector unsigned int); +int vec_any_ge (vector bool int, vector signed int); +int vec_any_ge (vector float, vector float); + +int vec_any_gt (vector bool char, vector unsigned char); +int vec_any_gt (vector unsigned char, vector bool char); +int vec_any_gt (vector unsigned char, vector unsigned char); +int vec_any_gt (vector bool char, vector signed char); +int vec_any_gt (vector signed char, vector bool char); +int vec_any_gt (vector signed char, vector signed char); +int vec_any_gt (vector bool short, vector unsigned short); +int vec_any_gt (vector unsigned short, vector bool short); +int vec_any_gt (vector unsigned short, vector unsigned short); +int vec_any_gt (vector bool short, vector signed short); +int vec_any_gt (vector signed short, vector bool short); +int vec_any_gt (vector signed short, vector signed short); +int vec_any_gt (vector bool int, vector unsigned int); +int vec_any_gt (vector unsigned int, vector bool int); +int vec_any_gt (vector unsigned int, vector unsigned int); +int vec_any_gt (vector bool int, vector signed int); +int vec_any_gt (vector signed int, vector bool int); +int vec_any_gt (vector signed int, vector signed int); +int vec_any_gt (vector float, vector float); + +int vec_any_le (vector bool char, vector unsigned char); +int vec_any_le (vector unsigned char, vector bool char); +int vec_any_le (vector unsigned char, vector unsigned char); +int vec_any_le (vector bool char, vector signed char); +int vec_any_le (vector signed char, vector bool char); +int vec_any_le (vector signed char, vector signed char); +int vec_any_le (vector bool short, vector unsigned short); +int vec_any_le (vector unsigned short, vector bool short); +int vec_any_le (vector unsigned short, vector unsigned short); +int vec_any_le (vector bool short, vector signed short); +int vec_any_le (vector signed short, vector bool short); +int vec_any_le (vector signed short, vector signed short); +int vec_any_le (vector bool int, vector unsigned int); +int vec_any_le (vector unsigned int, vector bool int); +int vec_any_le (vector unsigned int, vector unsigned int); +int vec_any_le (vector bool int, vector signed int); +int vec_any_le (vector signed int, vector bool int); +int vec_any_le (vector signed int, vector signed int); +int vec_any_le (vector float, vector float); + +int vec_any_lt (vector bool char, vector unsigned char); +int vec_any_lt (vector unsigned char, vector bool char); +int vec_any_lt (vector unsigned char, vector unsigned char); +int vec_any_lt (vector bool char, vector signed char); +int vec_any_lt (vector signed char, vector bool char); +int vec_any_lt (vector signed char, vector signed char); +int vec_any_lt (vector bool short, vector unsigned short); +int vec_any_lt (vector unsigned short, vector bool short); +int vec_any_lt (vector unsigned short, vector unsigned short); +int vec_any_lt (vector bool short, vector signed short); +int vec_any_lt (vector signed short, vector bool short); +int vec_any_lt (vector signed short, vector signed short); +int vec_any_lt (vector bool int, vector unsigned int); +int vec_any_lt (vector unsigned int, vector bool int); +int vec_any_lt (vector unsigned int, vector unsigned int); +int vec_any_lt (vector bool int, vector signed int); +int vec_any_lt (vector signed int, vector bool int); +int vec_any_lt (vector signed int, vector signed int); +int vec_any_lt (vector float, vector float); + +int vec_any_nan (vector float); + +int vec_any_ne (vector signed char, vector bool char); +int vec_any_ne (vector signed char, vector signed char); +int vec_any_ne (vector unsigned char, vector bool char); +int vec_any_ne (vector unsigned char, vector unsigned char); +int vec_any_ne (vector bool char, vector bool char); +int vec_any_ne (vector bool char, vector unsigned char); +int vec_any_ne (vector bool char, vector signed char); +int vec_any_ne (vector signed short, vector bool short); +int vec_any_ne (vector signed short, vector signed short); +int vec_any_ne (vector unsigned short, vector bool short); +int vec_any_ne (vector unsigned short, vector unsigned short); +int vec_any_ne (vector bool short, vector bool short); +int vec_any_ne (vector bool short, vector unsigned short); +int vec_any_ne (vector bool short, vector signed short); +int vec_any_ne (vector pixel, vector pixel); +int vec_any_ne (vector signed int, vector bool int); +int vec_any_ne (vector signed int, vector signed int); +int vec_any_ne (vector unsigned int, vector bool int); +int vec_any_ne (vector unsigned int, vector unsigned int); +int vec_any_ne (vector bool int, vector bool int); +int vec_any_ne (vector bool int, vector unsigned int); +int vec_any_ne (vector bool int, vector signed int); +int vec_any_ne (vector float, vector float); + +int vec_any_nge (vector float, vector float); + +int vec_any_ngt (vector float, vector float); + +int vec_any_nle (vector float, vector float); + +int vec_any_nlt (vector float, vector float); + +int vec_any_numeric (vector float); + +int vec_any_out (vector float, vector float); +@end smallexample + +If the vector/scalar (VSX) instruction set is available, the following +additional functions are available: + +@smallexample +vector double vec_abs (vector double); +vector double vec_add (vector double, vector double); +vector double vec_and (vector double, vector double); +vector double vec_and (vector double, vector bool long); +vector double vec_and (vector bool long, vector double); +vector double vec_andc (vector double, vector double); +vector double vec_andc (vector double, vector bool long); +vector double vec_andc (vector bool long, vector double); +vector double vec_ceil (vector double); +vector bool long vec_cmpeq (vector double, vector double); +vector bool long vec_cmpge (vector double, vector double); +vector bool long vec_cmpgt (vector double, vector double); +vector bool long vec_cmple (vector double, vector double); +vector bool long vec_cmplt (vector double, vector double); +vector float vec_div (vector float, vector float); +vector double vec_div (vector double, vector double); +vector double vec_floor (vector double); +vector double vec_ld (int, const vector double *); +vector double vec_ld (int, const double *); +vector double vec_ldl (int, const vector double *); +vector double vec_ldl (int, const double *); +vector unsigned char vec_lvsl (int, const volatile double *); +vector unsigned char vec_lvsr (int, const volatile double *); +vector double vec_madd (vector double, vector double, vector double); +vector double vec_max (vector double, vector double); +vector double vec_min (vector double, vector double); +vector float vec_msub (vector float, vector float, vector float); +vector double vec_msub (vector double, vector double, vector double); +vector float vec_mul (vector float, vector float); +vector double vec_mul (vector double, vector double); +vector float vec_nearbyint (vector float); +vector double vec_nearbyint (vector double); +vector float vec_nmadd (vector float, vector float, vector float); +vector double vec_nmadd (vector double, vector double, vector double); +vector double vec_nmsub (vector double, vector double, vector double); +vector double vec_nor (vector double, vector double); +vector double vec_or (vector double, vector double); +vector double vec_or (vector double, vector bool long); +vector double vec_or (vector bool long, vector double); +vector double vec_perm (vector double, + vector double, + vector unsigned char); +vector double vec_rint (vector double); +vector double vec_recip (vector double, vector double); +vector double vec_rsqrt (vector double); +vector double vec_rsqrte (vector double); +vector double vec_sel (vector double, vector double, vector bool long); +vector double vec_sel (vector double, vector double, vector unsigned long); +vector double vec_sub (vector double, vector double); +vector float vec_sqrt (vector float); +vector double vec_sqrt (vector double); +void vec_st (vector double, int, vector double *); +void vec_st (vector double, int, double *); +vector double vec_trunc (vector double); +vector double vec_xor (vector double, vector double); +vector double vec_xor (vector double, vector bool long); +vector double vec_xor (vector bool long, vector double); +int vec_all_eq (vector double, vector double); +int vec_all_ge (vector double, vector double); +int vec_all_gt (vector double, vector double); +int vec_all_le (vector double, vector double); +int vec_all_lt (vector double, vector double); +int vec_all_nan (vector double); +int vec_all_ne (vector double, vector double); +int vec_all_nge (vector double, vector double); +int vec_all_ngt (vector double, vector double); +int vec_all_nle (vector double, vector double); +int vec_all_nlt (vector double, vector double); +int vec_all_numeric (vector double); +int vec_any_eq (vector double, vector double); +int vec_any_ge (vector double, vector double); +int vec_any_gt (vector double, vector double); +int vec_any_le (vector double, vector double); +int vec_any_lt (vector double, vector double); +int vec_any_nan (vector double); +int vec_any_ne (vector double, vector double); +int vec_any_nge (vector double, vector double); +int vec_any_ngt (vector double, vector double); +int vec_any_nle (vector double, vector double); +int vec_any_nlt (vector double, vector double); +int vec_any_numeric (vector double); + +vector double vec_vsx_ld (int, const vector double *); +vector double vec_vsx_ld (int, const double *); +vector float vec_vsx_ld (int, const vector float *); +vector float vec_vsx_ld (int, const float *); +vector bool int vec_vsx_ld (int, const vector bool int *); +vector signed int vec_vsx_ld (int, const vector signed int *); +vector signed int vec_vsx_ld (int, const int *); +vector signed int vec_vsx_ld (int, const long *); +vector unsigned int vec_vsx_ld (int, const vector unsigned int *); +vector unsigned int vec_vsx_ld (int, const unsigned int *); +vector unsigned int vec_vsx_ld (int, const unsigned long *); +vector bool short vec_vsx_ld (int, const vector bool short *); +vector pixel vec_vsx_ld (int, const vector pixel *); +vector signed short vec_vsx_ld (int, const vector signed short *); +vector signed short vec_vsx_ld (int, const short *); +vector unsigned short vec_vsx_ld (int, const vector unsigned short *); +vector unsigned short vec_vsx_ld (int, const unsigned short *); +vector bool char vec_vsx_ld (int, const vector bool char *); +vector signed char vec_vsx_ld (int, const vector signed char *); +vector signed char vec_vsx_ld (int, const signed char *); +vector unsigned char vec_vsx_ld (int, const vector unsigned char *); +vector unsigned char vec_vsx_ld (int, const unsigned char *); + +void vec_vsx_st (vector double, int, vector double *); +void vec_vsx_st (vector double, int, double *); +void vec_vsx_st (vector float, int, vector float *); +void vec_vsx_st (vector float, int, float *); +void vec_vsx_st (vector signed int, int, vector signed int *); +void vec_vsx_st (vector signed int, int, int *); +void vec_vsx_st (vector unsigned int, int, vector unsigned int *); +void vec_vsx_st (vector unsigned int, int, unsigned int *); +void vec_vsx_st (vector bool int, int, vector bool int *); +void vec_vsx_st (vector bool int, int, unsigned int *); +void vec_vsx_st (vector bool int, int, int *); +void vec_vsx_st (vector signed short, int, vector signed short *); +void vec_vsx_st (vector signed short, int, short *); +void vec_vsx_st (vector unsigned short, int, vector unsigned short *); +void vec_vsx_st (vector unsigned short, int, unsigned short *); +void vec_vsx_st (vector bool short, int, vector bool short *); +void vec_vsx_st (vector bool short, int, unsigned short *); +void vec_vsx_st (vector pixel, int, vector pixel *); +void vec_vsx_st (vector pixel, int, unsigned short *); +void vec_vsx_st (vector pixel, int, short *); +void vec_vsx_st (vector bool short, int, short *); +void vec_vsx_st (vector signed char, int, vector signed char *); +void vec_vsx_st (vector signed char, int, signed char *); +void vec_vsx_st (vector unsigned char, int, vector unsigned char *); +void vec_vsx_st (vector unsigned char, int, unsigned char *); +void vec_vsx_st (vector bool char, int, vector bool char *); +void vec_vsx_st (vector bool char, int, unsigned char *); +void vec_vsx_st (vector bool char, int, signed char *); +@end smallexample + +Note that the @samp{vec_ld} and @samp{vec_st} builtins will always +generate the Altivec @samp{LVX} and @samp{STVX} instructions even +if the VSX instruction set is available. The @samp{vec_vsx_ld} and +@samp{vec_vsx_st} builtins will always generate the VSX @samp{LXVD2X}, +@samp{LXVW4X}, @samp{STXVD2X}, and @samp{STXVW4X} instructions. + +GCC provides a few other builtins on Powerpc to access certain instructions: +@smallexample +float __builtin_recipdivf (float, float); +float __builtin_rsqrtf (float); +double __builtin_recipdiv (double, double); +double __builtin_rsqrt (double); +long __builtin_bpermd (long, long); +int __builtin_bswap16 (int); +@end smallexample + +The @code{vec_rsqrt}, @code{__builtin_rsqrt}, and +@code{__builtin_rsqrtf} functions generate multiple instructions to +implement the reciprocal sqrt functionality using reciprocal sqrt +estimate instructions. + +The @code{__builtin_recipdiv}, and @code{__builtin_recipdivf} +functions generate multiple instructions to implement division using +the reciprocal estimate instructions. + +@node RX Built-in Functions +@subsection RX Built-in Functions +GCC supports some of the RX instructions which cannot be expressed in +the C programming language via the use of built-in functions. The +following functions are supported: + +@deftypefn {Built-in Function} void __builtin_rx_brk (void) +Generates the @code{brk} machine instruction. +@end deftypefn + +@deftypefn {Built-in Function} void __builtin_rx_clrpsw (int) +Generates the @code{clrpsw} machine instruction to clear the specified +bit in the processor status word. +@end deftypefn + +@deftypefn {Built-in Function} void __builtin_rx_int (int) +Generates the @code{int} machine instruction to generate an interrupt +with the specified value. +@end deftypefn + +@deftypefn {Built-in Function} void __builtin_rx_machi (int, int) +Generates the @code{machi} machine instruction to add the result of +multiplying the top 16-bits of the two arguments into the +accumulator. +@end deftypefn + +@deftypefn {Built-in Function} void __builtin_rx_maclo (int, int) +Generates the @code{maclo} machine instruction to add the result of +multiplying the bottom 16-bits of the two arguments into the +accumulator. +@end deftypefn + +@deftypefn {Built-in Function} void __builtin_rx_mulhi (int, int) +Generates the @code{mulhi} machine instruction to place the result of +multiplying the top 16-bits of the two arguments into the +accumulator. +@end deftypefn + +@deftypefn {Built-in Function} void __builtin_rx_mullo (int, int) +Generates the @code{mullo} machine instruction to place the result of +multiplying the bottom 16-bits of the two arguments into the +accumulator. +@end deftypefn + +@deftypefn {Built-in Function} int __builtin_rx_mvfachi (void) +Generates the @code{mvfachi} machine instruction to read the top +32-bits of the accumulator. +@end deftypefn + +@deftypefn {Built-in Function} int __builtin_rx_mvfacmi (void) +Generates the @code{mvfacmi} machine instruction to read the middle +32-bits of the accumulator. +@end deftypefn + +@deftypefn {Built-in Function} int __builtin_rx_mvfc (int) +Generates the @code{mvfc} machine instruction which reads the control +register specified in its argument and returns its value. +@end deftypefn + +@deftypefn {Built-in Function} void __builtin_rx_mvtachi (int) +Generates the @code{mvtachi} machine instruction to set the top +32-bits of the accumulator. +@end deftypefn + +@deftypefn {Built-in Function} void __builtin_rx_mvtaclo (int) +Generates the @code{mvtaclo} machine instruction to set the bottom +32-bits of the accumulator. +@end deftypefn + +@deftypefn {Built-in Function} void __builtin_rx_mvtc (int reg, int val) +Generates the @code{mvtc} machine instruction which sets control +register number @code{reg} to @code{val}. +@end deftypefn + +@deftypefn {Built-in Function} void __builtin_rx_mvtipl (int) +Generates the @code{mvtipl} machine instruction set the interrupt +priority level. +@end deftypefn + +@deftypefn {Built-in Function} void __builtin_rx_racw (int) +Generates the @code{racw} machine instruction to round the accumulator +according to the specified mode. +@end deftypefn + +@deftypefn {Built-in Function} int __builtin_rx_revw (int) +Generates the @code{revw} machine instruction which swaps the bytes in +the argument so that bits 0--7 now occupy bits 8--15 and vice versa, +and also bits 16--23 occupy bits 24--31 and vice versa. +@end deftypefn + +@deftypefn {Built-in Function} void __builtin_rx_rmpa (void) +Generates the @code{rmpa} machine instruction which initiates a +repeated multiply and accumulate sequence. +@end deftypefn + +@deftypefn {Built-in Function} void __builtin_rx_round (float) +Generates the @code{round} machine instruction which returns the +floating point argument rounded according to the current rounding mode +set in the floating point status word register. +@end deftypefn + +@deftypefn {Built-in Function} int __builtin_rx_sat (int) +Generates the @code{sat} machine instruction which returns the +saturated value of the argument. +@end deftypefn + +@deftypefn {Built-in Function} void __builtin_rx_setpsw (int) +Generates the @code{setpsw} machine instruction to set the specified +bit in the processor status word. +@end deftypefn + +@deftypefn {Built-in Function} void __builtin_rx_wait (void) +Generates the @code{wait} machine instruction. +@end deftypefn + +@node SPARC VIS Built-in Functions +@subsection SPARC VIS Built-in Functions + +GCC supports SIMD operations on the SPARC using both the generic vector +extensions (@pxref{Vector Extensions}) as well as built-in functions for +the SPARC Visual Instruction Set (VIS). When you use the @option{-mvis} +switch, the VIS extension is exposed as the following built-in functions: + +@smallexample +typedef int v2si __attribute__ ((vector_size (8))); +typedef short v4hi __attribute__ ((vector_size (8))); +typedef short v2hi __attribute__ ((vector_size (4))); +typedef char v8qi __attribute__ ((vector_size (8))); +typedef char v4qi __attribute__ ((vector_size (4))); + +void * __builtin_vis_alignaddr (void *, long); +int64_t __builtin_vis_faligndatadi (int64_t, int64_t); +v2si __builtin_vis_faligndatav2si (v2si, v2si); +v4hi __builtin_vis_faligndatav4hi (v4si, v4si); +v8qi __builtin_vis_faligndatav8qi (v8qi, v8qi); + +v4hi __builtin_vis_fexpand (v4qi); + +v4hi __builtin_vis_fmul8x16 (v4qi, v4hi); +v4hi __builtin_vis_fmul8x16au (v4qi, v4hi); +v4hi __builtin_vis_fmul8x16al (v4qi, v4hi); +v4hi __builtin_vis_fmul8sux16 (v8qi, v4hi); +v4hi __builtin_vis_fmul8ulx16 (v8qi, v4hi); +v2si __builtin_vis_fmuld8sux16 (v4qi, v2hi); +v2si __builtin_vis_fmuld8ulx16 (v4qi, v2hi); + +v4qi __builtin_vis_fpack16 (v4hi); +v8qi __builtin_vis_fpack32 (v2si, v2si); +v2hi __builtin_vis_fpackfix (v2si); +v8qi __builtin_vis_fpmerge (v4qi, v4qi); + +int64_t __builtin_vis_pdist (v8qi, v8qi, int64_t); +@end smallexample + +@node SPU Built-in Functions +@subsection SPU Built-in Functions + +GCC provides extensions for the SPU processor as described in the +Sony/Toshiba/IBM SPU Language Extensions Specification, which can be +found at @uref{http://cell.scei.co.jp/} or +@uref{http://www.ibm.com/developerworks/power/cell/}. GCC's +implementation differs in several ways. + +@itemize @bullet + +@item +The optional extension of specifying vector constants in parentheses is +not supported. + +@item +A vector initializer requires no cast if the vector constant is of the +same type as the variable it is initializing. + +@item +If @code{signed} or @code{unsigned} is omitted, the signedness of the +vector type is the default signedness of the base type. The default +varies depending on the operating system, so a portable program should +always specify the signedness. + +@item +By default, the keyword @code{__vector} is added. The macro +@code{vector} is defined in @code{<spu_intrinsics.h>} and can be +undefined. + +@item +GCC allows using a @code{typedef} name as the type specifier for a +vector type. + +@item +For C, overloaded functions are implemented with macros so the following +does not work: + +@smallexample + spu_add ((vector signed int)@{1, 2, 3, 4@}, foo); +@end smallexample + +Since @code{spu_add} is a macro, the vector constant in the example +is treated as four separate arguments. Wrap the entire argument in +parentheses for this to work. + +@item +The extended version of @code{__builtin_expect} is not supported. + +@end itemize + +@emph{Note:} Only the interface described in the aforementioned +specification is supported. Internally, GCC uses built-in functions to +implement the required functionality, but these are not supported and +are subject to change without notice. + +@node Target Format Checks +@section Format Checks Specific to Particular Target Machines + +For some target machines, GCC supports additional options to the +format attribute +(@pxref{Function Attributes,,Declaring Attributes of Functions}). + +@menu +* Solaris Format Checks:: +* Darwin Format Checks:: +@end menu + +@node Solaris Format Checks +@subsection Solaris Format Checks + +Solaris targets support the @code{cmn_err} (or @code{__cmn_err__}) format +check. @code{cmn_err} accepts a subset of the standard @code{printf} +conversions, and the two-argument @code{%b} conversion for displaying +bit-fields. See the Solaris man page for @code{cmn_err} for more information. + +@node Darwin Format Checks +@subsection Darwin Format Checks + +Darwin targets support the @code{CFString} (or @code{__CFString__}) in the format +attribute context. Declarations made with such attribution will be parsed for correct syntax +and format argument types. However, parsing of the format string itself is currently undefined +and will not be carried out by this version of the compiler. + +Additionally, @code{CFStringRefs} (defined by the @code{CoreFoundation} headers) may +also be used as format arguments. Note that the relevant headers are only likely to be +available on Darwin (OSX) installations. On such installations, the XCode and system +documentation provide descriptions of @code{CFString}, @code{CFStringRefs} and +associated functions. + +@node Pragmas +@section Pragmas Accepted by GCC +@cindex pragmas +@cindex @code{#pragma} + +GCC supports several types of pragmas, primarily in order to compile +code originally written for other compilers. Note that in general +we do not recommend the use of pragmas; @xref{Function Attributes}, +for further explanation. + +@menu +* ARM Pragmas:: +* M32C Pragmas:: +* MeP Pragmas:: +* RS/6000 and PowerPC Pragmas:: +* Darwin Pragmas:: +* Solaris Pragmas:: +* Symbol-Renaming Pragmas:: +* Structure-Packing Pragmas:: +* Weak Pragmas:: +* Diagnostic Pragmas:: +* Visibility Pragmas:: +* Push/Pop Macro Pragmas:: +* Function Specific Option Pragmas:: +@end menu + +@node ARM Pragmas +@subsection ARM Pragmas + +The ARM target defines pragmas for controlling the default addition of +@code{long_call} and @code{short_call} attributes to functions. +@xref{Function Attributes}, for information about the effects of these +attributes. + +@table @code +@item long_calls +@cindex pragma, long_calls +Set all subsequent functions to have the @code{long_call} attribute. + +@item no_long_calls +@cindex pragma, no_long_calls +Set all subsequent functions to have the @code{short_call} attribute. + +@item long_calls_off +@cindex pragma, long_calls_off +Do not affect the @code{long_call} or @code{short_call} attributes of +subsequent functions. +@end table + +@node M32C Pragmas +@subsection M32C Pragmas + +@table @code +@item GCC memregs @var{number} +@cindex pragma, memregs +Overrides the command-line option @code{-memregs=} for the current +file. Use with care! This pragma must be before any function in the +file, and mixing different memregs values in different objects may +make them incompatible. This pragma is useful when a +performance-critical function uses a memreg for temporary values, +as it may allow you to reduce the number of memregs used. + +@item ADDRESS @var{name} @var{address} +@cindex pragma, address +For any declared symbols matching @var{name}, this does three things +to that symbol: it forces the symbol to be located at the given +address (a number), it forces the symbol to be volatile, and it +changes the symbol's scope to be static. This pragma exists for +compatibility with other compilers, but note that the common +@code{1234H} numeric syntax is not supported (use @code{0x1234} +instead). Example: + +@example +#pragma ADDRESS port3 0x103 +char port3; +@end example + +@end table + +@node MeP Pragmas +@subsection MeP Pragmas + +@table @code + +@item custom io_volatile (on|off) +@cindex pragma, custom io_volatile +Overrides the command line option @code{-mio-volatile} for the current +file. Note that for compatibility with future GCC releases, this +option should only be used once before any @code{io} variables in each +file. + +@item GCC coprocessor available @var{registers} +@cindex pragma, coprocessor available +Specifies which coprocessor registers are available to the register +allocator. @var{registers} may be a single register, register range +separated by ellipses, or comma-separated list of those. Example: + +@example +#pragma GCC coprocessor available $c0...$c10, $c28 +@end example + +@item GCC coprocessor call_saved @var{registers} +@cindex pragma, coprocessor call_saved +Specifies which coprocessor registers are to be saved and restored by +any function using them. @var{registers} may be a single register, +register range separated by ellipses, or comma-separated list of +those. Example: + +@example +#pragma GCC coprocessor call_saved $c4...$c6, $c31 +@end example + +@item GCC coprocessor subclass '(A|B|C|D)' = @var{registers} +@cindex pragma, coprocessor subclass +Creates and defines a register class. These register classes can be +used by inline @code{asm} constructs. @var{registers} may be a single +register, register range separated by ellipses, or comma-separated +list of those. Example: + +@example +#pragma GCC coprocessor subclass 'B' = $c2, $c4, $c6 + +asm ("cpfoo %0" : "=B" (x)); +@end example + +@item GCC disinterrupt @var{name} , @var{name} @dots{} +@cindex pragma, disinterrupt +For the named functions, the compiler adds code to disable interrupts +for the duration of those functions. Any functions so named, which +are not encountered in the source, cause a warning that the pragma was +not used. Examples: + +@example +#pragma disinterrupt foo +#pragma disinterrupt bar, grill +int foo () @{ @dots{} @} +@end example + +@item GCC call @var{name} , @var{name} @dots{} +@cindex pragma, call +For the named functions, the compiler always uses a register-indirect +call model when calling the named functions. Examples: + +@example +extern int foo (); +#pragma call foo +@end example + +@end table + +@node RS/6000 and PowerPC Pragmas +@subsection RS/6000 and PowerPC Pragmas + +The RS/6000 and PowerPC targets define one pragma for controlling +whether or not the @code{longcall} attribute is added to function +declarations by default. This pragma overrides the @option{-mlongcall} +option, but not the @code{longcall} and @code{shortcall} attributes. +@xref{RS/6000 and PowerPC Options}, for more information about when long +calls are and are not necessary. + +@table @code +@item longcall (1) +@cindex pragma, longcall +Apply the @code{longcall} attribute to all subsequent function +declarations. + +@item longcall (0) +Do not apply the @code{longcall} attribute to subsequent function +declarations. +@end table + +@c Describe h8300 pragmas here. +@c Describe sh pragmas here. +@c Describe v850 pragmas here. + +@node Darwin Pragmas +@subsection Darwin Pragmas + +The following pragmas are available for all architectures running the +Darwin operating system. These are useful for compatibility with other +Mac OS compilers. + +@table @code +@item mark @var{tokens}@dots{} +@cindex pragma, mark +This pragma is accepted, but has no effect. + +@item options align=@var{alignment} +@cindex pragma, options align +This pragma sets the alignment of fields in structures. The values of +@var{alignment} may be @code{mac68k}, to emulate m68k alignment, or +@code{power}, to emulate PowerPC alignment. Uses of this pragma nest +properly; to restore the previous setting, use @code{reset} for the +@var{alignment}. + +@item segment @var{tokens}@dots{} +@cindex pragma, segment +This pragma is accepted, but has no effect. + +@item unused (@var{var} [, @var{var}]@dots{}) +@cindex pragma, unused +This pragma declares variables to be possibly unused. GCC will not +produce warnings for the listed variables. The effect is similar to +that of the @code{unused} attribute, except that this pragma may appear +anywhere within the variables' scopes. +@end table + +@node Solaris Pragmas +@subsection Solaris Pragmas + +The Solaris target supports @code{#pragma redefine_extname} +(@pxref{Symbol-Renaming Pragmas}). It also supports additional +@code{#pragma} directives for compatibility with the system compiler. + +@table @code +@item align @var{alignment} (@var{variable} [, @var{variable}]...) +@cindex pragma, align + +Increase the minimum alignment of each @var{variable} to @var{alignment}. +This is the same as GCC's @code{aligned} attribute @pxref{Variable +Attributes}). Macro expansion occurs on the arguments to this pragma +when compiling C and Objective-C@. It does not currently occur when +compiling C++, but this is a bug which may be fixed in a future +release. + +@item fini (@var{function} [, @var{function}]...) +@cindex pragma, fini + +This pragma causes each listed @var{function} to be called after +main, or during shared module unloading, by adding a call to the +@code{.fini} section. + +@item init (@var{function} [, @var{function}]...) +@cindex pragma, init + +This pragma causes each listed @var{function} to be called during +initialization (before @code{main}) or during shared module loading, by +adding a call to the @code{.init} section. + +@end table + +@node Symbol-Renaming Pragmas +@subsection Symbol-Renaming Pragmas + +For compatibility with the Solaris and Tru64 UNIX system headers, GCC +supports two @code{#pragma} directives which change the name used in +assembly for a given declaration. @code{#pragma extern_prefix} is only +available on platforms whose system headers need it. To get this effect +on all platforms supported by GCC, use the asm labels extension (@pxref{Asm +Labels}). + +@table @code +@item redefine_extname @var{oldname} @var{newname} +@cindex pragma, redefine_extname + +This pragma gives the C function @var{oldname} the assembly symbol +@var{newname}. The preprocessor macro @code{__PRAGMA_REDEFINE_EXTNAME} +will be defined if this pragma is available (currently on all platforms). + +@item extern_prefix @var{string} +@cindex pragma, extern_prefix + +This pragma causes all subsequent external function and variable +declarations to have @var{string} prepended to their assembly symbols. +This effect may be terminated with another @code{extern_prefix} pragma +whose argument is an empty string. The preprocessor macro +@code{__PRAGMA_EXTERN_PREFIX} will be defined if this pragma is +available (currently only on Tru64 UNIX)@. +@end table + +These pragmas and the asm labels extension interact in a complicated +manner. Here are some corner cases you may want to be aware of. + +@enumerate +@item Both pragmas silently apply only to declarations with external +linkage. Asm labels do not have this restriction. + +@item In C++, both pragmas silently apply only to declarations with +``C'' linkage. Again, asm labels do not have this restriction. + +@item If any of the three ways of changing the assembly name of a +declaration is applied to a declaration whose assembly name has +already been determined (either by a previous use of one of these +features, or because the compiler needed the assembly name in order to +generate code), and the new name is different, a warning issues and +the name does not change. + +@item The @var{oldname} used by @code{#pragma redefine_extname} is +always the C-language name. + +@item If @code{#pragma extern_prefix} is in effect, and a declaration +occurs with an asm label attached, the prefix is silently ignored for +that declaration. + +@item If @code{#pragma extern_prefix} and @code{#pragma redefine_extname} +apply to the same declaration, whichever triggered first wins, and a +warning issues if they contradict each other. (We would like to have +@code{#pragma redefine_extname} always win, for consistency with asm +labels, but if @code{#pragma extern_prefix} triggers first we have no +way of knowing that that happened.) +@end enumerate + +@node Structure-Packing Pragmas +@subsection Structure-Packing Pragmas + +For compatibility with Microsoft Windows compilers, GCC supports a +set of @code{#pragma} directives which change the maximum alignment of +members of structures (other than zero-width bitfields), unions, and +classes subsequently defined. The @var{n} value below always is required +to be a small power of two and specifies the new alignment in bytes. + +@enumerate +@item @code{#pragma pack(@var{n})} simply sets the new alignment. +@item @code{#pragma pack()} sets the alignment to the one that was in +effect when compilation started (see also command-line option +@option{-fpack-struct[=@var{n}]} @pxref{Code Gen Options}). +@item @code{#pragma pack(push[,@var{n}])} pushes the current alignment +setting on an internal stack and then optionally sets the new alignment. +@item @code{#pragma pack(pop)} restores the alignment setting to the one +saved at the top of the internal stack (and removes that stack entry). +Note that @code{#pragma pack([@var{n}])} does not influence this internal +stack; thus it is possible to have @code{#pragma pack(push)} followed by +multiple @code{#pragma pack(@var{n})} instances and finalized by a single +@code{#pragma pack(pop)}. +@end enumerate + +Some targets, e.g.@: i386 and powerpc, support the @code{ms_struct} +@code{#pragma} which lays out a structure as the documented +@code{__attribute__ ((ms_struct))}. +@enumerate +@item @code{#pragma ms_struct on} turns on the layout for structures +declared. +@item @code{#pragma ms_struct off} turns off the layout for structures +declared. +@item @code{#pragma ms_struct reset} goes back to the default layout. +@end enumerate + +@node Weak Pragmas +@subsection Weak Pragmas + +For compatibility with SVR4, GCC supports a set of @code{#pragma} +directives for declaring symbols to be weak, and defining weak +aliases. + +@table @code +@item #pragma weak @var{symbol} +@cindex pragma, weak +This pragma declares @var{symbol} to be weak, as if the declaration +had the attribute of the same name. The pragma may appear before +or after the declaration of @var{symbol}. It is not an error for +@var{symbol} to never be defined at all. + +@item #pragma weak @var{symbol1} = @var{symbol2} +This pragma declares @var{symbol1} to be a weak alias of @var{symbol2}. +It is an error if @var{symbol2} is not defined in the current +translation unit. +@end table + +@node Diagnostic Pragmas +@subsection Diagnostic Pragmas + +GCC allows the user to selectively enable or disable certain types of +diagnostics, and change the kind of the diagnostic. For example, a +project's policy might require that all sources compile with +@option{-Werror} but certain files might have exceptions allowing +specific types of warnings. Or, a project might selectively enable +diagnostics and treat them as errors depending on which preprocessor +macros are defined. + +@table @code +@item #pragma GCC diagnostic @var{kind} @var{option} +@cindex pragma, diagnostic + +Modifies the disposition of a diagnostic. Note that not all +diagnostics are modifiable; at the moment only warnings (normally +controlled by @samp{-W@dots{}}) can be controlled, and not all of them. +Use @option{-fdiagnostics-show-option} to determine which diagnostics +are controllable and which option controls them. + +@var{kind} is @samp{error} to treat this diagnostic as an error, +@samp{warning} to treat it like a warning (even if @option{-Werror} is +in effect), or @samp{ignored} if the diagnostic is to be ignored. +@var{option} is a double quoted string which matches the command-line +option. + +@example +#pragma GCC diagnostic warning "-Wformat" +#pragma GCC diagnostic error "-Wformat" +#pragma GCC diagnostic ignored "-Wformat" +@end example + +Note that these pragmas override any command-line options. GCC keeps +track of the location of each pragma, and issues diagnostics according +to the state as of that point in the source file. Thus, pragmas occurring +after a line do not affect diagnostics caused by that line. + +@item #pragma GCC diagnostic push +@itemx #pragma GCC diagnostic pop + +Causes GCC to remember the state of the diagnostics as of each +@code{push}, and restore to that point at each @code{pop}. If a +@code{pop} has no matching @code{push}, the command line options are +restored. + +@example +#pragma GCC diagnostic error "-Wuninitialized" + foo(a); /* error is given for this one */ +#pragma GCC diagnostic push +#pragma GCC diagnostic ignored "-Wuninitialized" + foo(b); /* no diagnostic for this one */ +#pragma GCC diagnostic pop + foo(c); /* error is given for this one */ +#pragma GCC diagnostic pop + foo(d); /* depends on command line options */ +@end example + +@end table + +GCC also offers a simple mechanism for printing messages during +compilation. + +@table @code +@item #pragma message @var{string} +@cindex pragma, diagnostic + +Prints @var{string} as a compiler message on compilation. The message +is informational only, and is neither a compilation warning nor an error. + +@smallexample +#pragma message "Compiling " __FILE__ "..." +@end smallexample + +@var{string} may be parenthesized, and is printed with location +information. For example, + +@smallexample +#define DO_PRAGMA(x) _Pragma (#x) +#define TODO(x) DO_PRAGMA(message ("TODO - " #x)) + +TODO(Remember to fix this) +@end smallexample + +prints @samp{/tmp/file.c:4: note: #pragma message: +TODO - Remember to fix this}. + +@end table + +@node Visibility Pragmas +@subsection Visibility Pragmas + +@table @code +@item #pragma GCC visibility push(@var{visibility}) +@itemx #pragma GCC visibility pop +@cindex pragma, visibility + +This pragma allows the user to set the visibility for multiple +declarations without having to give each a visibility attribute +@xref{Function Attributes}, for more information about visibility and +the attribute syntax. + +In C++, @samp{#pragma GCC visibility} affects only namespace-scope +declarations. Class members and template specializations are not +affected; if you want to override the visibility for a particular +member or instantiation, you must use an attribute. + +@end table + + +@node Push/Pop Macro Pragmas +@subsection Push/Pop Macro Pragmas + +For compatibility with Microsoft Windows compilers, GCC supports +@samp{#pragma push_macro(@var{"macro_name"})} +and @samp{#pragma pop_macro(@var{"macro_name"})}. + +@table @code +@item #pragma push_macro(@var{"macro_name"}) +@cindex pragma, push_macro +This pragma saves the value of the macro named as @var{macro_name} to +the top of the stack for this macro. + +@item #pragma pop_macro(@var{"macro_name"}) +@cindex pragma, pop_macro +This pragma sets the value of the macro named as @var{macro_name} to +the value on top of the stack for this macro. If the stack for +@var{macro_name} is empty, the value of the macro remains unchanged. +@end table + +For example: + +@smallexample +#define X 1 +#pragma push_macro("X") +#undef X +#define X -1 +#pragma pop_macro("X") +int x [X]; +@end smallexample + +In this example, the definition of X as 1 is saved by @code{#pragma +push_macro} and restored by @code{#pragma pop_macro}. + +@node Function Specific Option Pragmas +@subsection Function Specific Option Pragmas + +@table @code +@item #pragma GCC target (@var{"string"}...) +@cindex pragma GCC target + +This pragma allows you to set target specific options for functions +defined later in the source file. One or more strings can be +specified. Each function that is defined after this point will be as +if @code{attribute((target("STRING")))} was specified for that +function. The parenthesis around the options is optional. +@xref{Function Attributes}, for more information about the +@code{target} attribute and the attribute syntax. + +The @code{#pragma GCC target} attribute is not implemented in GCC versions earlier +than 4.4 for the i386/x86_64 and 4.6 for the PowerPC backends. At +present, it is not implemented for other backends. +@end table + +@table @code +@item #pragma GCC optimize (@var{"string"}...) +@cindex pragma GCC optimize + +This pragma allows you to set global optimization options for functions +defined later in the source file. One or more strings can be +specified. Each function that is defined after this point will be as +if @code{attribute((optimize("STRING")))} was specified for that +function. The parenthesis around the options is optional. +@xref{Function Attributes}, for more information about the +@code{optimize} attribute and the attribute syntax. + +The @samp{#pragma GCC optimize} pragma is not implemented in GCC +versions earlier than 4.4. +@end table + +@table @code +@item #pragma GCC push_options +@itemx #pragma GCC pop_options +@cindex pragma GCC push_options +@cindex pragma GCC pop_options + +These pragmas maintain a stack of the current target and optimization +options. It is intended for include files where you temporarily want +to switch to using a different @samp{#pragma GCC target} or +@samp{#pragma GCC optimize} and then to pop back to the previous +options. + +The @samp{#pragma GCC push_options} and @samp{#pragma GCC pop_options} +pragmas are not implemented in GCC versions earlier than 4.4. +@end table + +@table @code +@item #pragma GCC reset_options +@cindex pragma GCC reset_options + +This pragma clears the current @code{#pragma GCC target} and +@code{#pragma GCC optimize} to use the default switches as specified +on the command line. + +The @samp{#pragma GCC reset_options} pragma is not implemented in GCC +versions earlier than 4.4. +@end table + +@node Unnamed Fields +@section Unnamed struct/union fields within structs/unions +@cindex @code{struct} +@cindex @code{union} + +As permitted by ISO C1X and for compatibility with other compilers, +GCC allows you to define +a structure or union that contains, as fields, structures and unions +without names. For example: + +@smallexample +struct @{ + int a; + union @{ + int b; + float c; + @}; + int d; +@} foo; +@end smallexample + +In this example, the user would be able to access members of the unnamed +union with code like @samp{foo.b}. Note that only unnamed structs and +unions are allowed, you may not have, for example, an unnamed +@code{int}. + +You must never create such structures that cause ambiguous field definitions. +For example, this structure: + +@smallexample +struct @{ + int a; + struct @{ + int a; + @}; +@} foo; +@end smallexample + +It is ambiguous which @code{a} is being referred to with @samp{foo.a}. +The compiler gives errors for such constructs. + +@opindex fms-extensions +Unless @option{-fms-extensions} is used, the unnamed field must be a +structure or union definition without a tag (for example, @samp{struct +@{ int a; @};}). If @option{-fms-extensions} is used, the field may +also be a definition with a tag such as @samp{struct foo @{ int a; +@};}, a reference to a previously defined structure or union such as +@samp{struct foo;}, or a reference to a @code{typedef} name for a +previously defined structure or union type. + +@opindex fplan9-extensions +The option @option{-fplan9-extensions} enables +@option{-fms-extensions} as well as two other extensions. First, a +pointer to a structure is automatically converted to a pointer to an +anonymous field for assignments and function calls. For example: + +@smallexample +struct s1 @{ int a; @}; +struct s2 @{ struct s1; @}; +extern void f1 (struct s1 *); +void f2 (struct s2 *p) @{ f1 (p); @} +@end smallexample + +In the call to @code{f1} inside @code{f2}, the pointer @code{p} is +converted into a pointer to the anonymous field. + +Second, when the type of an anonymous field is a @code{typedef} for a +@code{struct} or @code{union}, code may refer to the field using the +name of the @code{typedef}. + +@smallexample +typedef struct @{ int a; @} s1; +struct s2 @{ s1; @}; +s1 f1 (struct s2 *p) @{ return p->s1; @} +@end smallexample + +These usages are only permitted when they are not ambiguous. + +@node Thread-Local +@section Thread-Local Storage +@cindex Thread-Local Storage +@cindex @acronym{TLS} +@cindex @code{__thread} + +Thread-local storage (@acronym{TLS}) is a mechanism by which variables +are allocated such that there is one instance of the variable per extant +thread. The run-time model GCC uses to implement this originates +in the IA-64 processor-specific ABI, but has since been migrated +to other processors as well. It requires significant support from +the linker (@command{ld}), dynamic linker (@command{ld.so}), and +system libraries (@file{libc.so} and @file{libpthread.so}), so it +is not available everywhere. + +At the user level, the extension is visible with a new storage +class keyword: @code{__thread}. For example: + +@smallexample +__thread int i; +extern __thread struct state s; +static __thread char *p; +@end smallexample + +The @code{__thread} specifier may be used alone, with the @code{extern} +or @code{static} specifiers, but with no other storage class specifier. +When used with @code{extern} or @code{static}, @code{__thread} must appear +immediately after the other storage class specifier. + +The @code{__thread} specifier may be applied to any global, file-scoped +static, function-scoped static, or static data member of a class. It may +not be applied to block-scoped automatic or non-static data member. + +When the address-of operator is applied to a thread-local variable, it is +evaluated at run-time and returns the address of the current thread's +instance of that variable. An address so obtained may be used by any +thread. When a thread terminates, any pointers to thread-local variables +in that thread become invalid. + +No static initialization may refer to the address of a thread-local variable. + +In C++, if an initializer is present for a thread-local variable, it must +be a @var{constant-expression}, as defined in 5.19.2 of the ANSI/ISO C++ +standard. + +See @uref{http://www.akkadia.org/drepper/tls.pdf, +ELF Handling For Thread-Local Storage} for a detailed explanation of +the four thread-local storage addressing models, and how the run-time +is expected to function. + +@menu +* C99 Thread-Local Edits:: +* C++98 Thread-Local Edits:: +@end menu + +@node C99 Thread-Local Edits +@subsection ISO/IEC 9899:1999 Edits for Thread-Local Storage + +The following are a set of changes to ISO/IEC 9899:1999 (aka C99) +that document the exact semantics of the language extension. + +@itemize @bullet +@item +@cite{5.1.2 Execution environments} + +Add new text after paragraph 1 + +@quotation +Within either execution environment, a @dfn{thread} is a flow of +control within a program. It is implementation defined whether +or not there may be more than one thread associated with a program. +It is implementation defined how threads beyond the first are +created, the name and type of the function called at thread +startup, and how threads may be terminated. However, objects +with thread storage duration shall be initialized before thread +startup. +@end quotation + +@item +@cite{6.2.4 Storage durations of objects} + +Add new text before paragraph 3 + +@quotation +An object whose identifier is declared with the storage-class +specifier @w{@code{__thread}} has @dfn{thread storage duration}. +Its lifetime is the entire execution of the thread, and its +stored value is initialized only once, prior to thread startup. +@end quotation + +@item +@cite{6.4.1 Keywords} + +Add @code{__thread}. + +@item +@cite{6.7.1 Storage-class specifiers} + +Add @code{__thread} to the list of storage class specifiers in +paragraph 1. + +Change paragraph 2 to + +@quotation +With the exception of @code{__thread}, at most one storage-class +specifier may be given [@dots{}]. The @code{__thread} specifier may +be used alone, or immediately following @code{extern} or +@code{static}. +@end quotation + +Add new text after paragraph 6 + +@quotation +The declaration of an identifier for a variable that has +block scope that specifies @code{__thread} shall also +specify either @code{extern} or @code{static}. + +The @code{__thread} specifier shall be used only with +variables. +@end quotation +@end itemize + +@node C++98 Thread-Local Edits +@subsection ISO/IEC 14882:1998 Edits for Thread-Local Storage + +The following are a set of changes to ISO/IEC 14882:1998 (aka C++98) +that document the exact semantics of the language extension. + +@itemize @bullet +@item +@b{[intro.execution]} + +New text after paragraph 4 + +@quotation +A @dfn{thread} is a flow of control within the abstract machine. +It is implementation defined whether or not there may be more than +one thread. +@end quotation + +New text after paragraph 7 + +@quotation +It is unspecified whether additional action must be taken to +ensure when and whether side effects are visible to other threads. +@end quotation + +@item +@b{[lex.key]} + +Add @code{__thread}. + +@item +@b{[basic.start.main]} + +Add after paragraph 5 + +@quotation +The thread that begins execution at the @code{main} function is called +the @dfn{main thread}. It is implementation defined how functions +beginning threads other than the main thread are designated or typed. +A function so designated, as well as the @code{main} function, is called +a @dfn{thread startup function}. It is implementation defined what +happens if a thread startup function returns. It is implementation +defined what happens to other threads when any thread calls @code{exit}. +@end quotation + +@item +@b{[basic.start.init]} + +Add after paragraph 4 + +@quotation +The storage for an object of thread storage duration shall be +statically initialized before the first statement of the thread startup +function. An object of thread storage duration shall not require +dynamic initialization. +@end quotation + +@item +@b{[basic.start.term]} + +Add after paragraph 3 + +@quotation +The type of an object with thread storage duration shall not have a +non-trivial destructor, nor shall it be an array type whose elements +(directly or indirectly) have non-trivial destructors. +@end quotation + +@item +@b{[basic.stc]} + +Add ``thread storage duration'' to the list in paragraph 1. + +Change paragraph 2 + +@quotation +Thread, static, and automatic storage durations are associated with +objects introduced by declarations [@dots{}]. +@end quotation + +Add @code{__thread} to the list of specifiers in paragraph 3. + +@item +@b{[basic.stc.thread]} + +New section before @b{[basic.stc.static]} + +@quotation +The keyword @code{__thread} applied to a non-local object gives the +object thread storage duration. + +A local variable or class data member declared both @code{static} +and @code{__thread} gives the variable or member thread storage +duration. +@end quotation + +@item +@b{[basic.stc.static]} + +Change paragraph 1 + +@quotation +All objects which have neither thread storage duration, dynamic +storage duration nor are local [@dots{}]. +@end quotation + +@item +@b{[dcl.stc]} + +Add @code{__thread} to the list in paragraph 1. + +Change paragraph 1 + +@quotation +With the exception of @code{__thread}, at most one +@var{storage-class-specifier} shall appear in a given +@var{decl-specifier-seq}. The @code{__thread} specifier may +be used alone, or immediately following the @code{extern} or +@code{static} specifiers. [@dots{}] +@end quotation + +Add after paragraph 5 + +@quotation +The @code{__thread} specifier can be applied only to the names of objects +and to anonymous unions. +@end quotation + +@item +@b{[class.mem]} + +Add after paragraph 6 + +@quotation +Non-@code{static} members shall not be @code{__thread}. +@end quotation +@end itemize + +@node Binary constants +@section Binary constants using the @samp{0b} prefix +@cindex Binary constants using the @samp{0b} prefix + +Integer constants can be written as binary constants, consisting of a +sequence of @samp{0} and @samp{1} digits, prefixed by @samp{0b} or +@samp{0B}. This is particularly useful in environments that operate a +lot on the bit-level (like microcontrollers). + +The following statements are identical: + +@smallexample +i = 42; +i = 0x2a; +i = 052; +i = 0b101010; +@end smallexample + +The type of these constants follows the same rules as for octal or +hexadecimal integer constants, so suffixes like @samp{L} or @samp{UL} +can be applied. + +@node C++ Extensions +@chapter Extensions to the C++ Language +@cindex extensions, C++ language +@cindex C++ language extensions + +The GNU compiler provides these extensions to the C++ language (and you +can also use most of the C language extensions in your C++ programs). If you +want to write code that checks whether these features are available, you can +test for the GNU compiler the same way as for C programs: check for a +predefined macro @code{__GNUC__}. You can also use @code{__GNUG__} to +test specifically for GNU C++ (@pxref{Common Predefined Macros,, +Predefined Macros,cpp,The GNU C Preprocessor}). + +@menu +* C++ Volatiles:: What constitutes an access to a volatile object. +* Restricted Pointers:: C99 restricted pointers and references. +* Vague Linkage:: Where G++ puts inlines, vtables and such. +* C++ Interface:: You can use a single C++ header file for both + declarations and definitions. +* Template Instantiation:: Methods for ensuring that exactly one copy of + each needed template instantiation is emitted. +* Bound member functions:: You can extract a function pointer to the + method denoted by a @samp{->*} or @samp{.*} expression. +* C++ Attributes:: Variable, function, and type attributes for C++ only. +* Namespace Association:: Strong using-directives for namespace association. +* Type Traits:: Compiler support for type traits +* Java Exceptions:: Tweaking exception handling to work with Java. +* Deprecated Features:: Things will disappear from g++. +* Backwards Compatibility:: Compatibilities with earlier definitions of C++. +@end menu + +@node C++ Volatiles +@section When is a Volatile C++ Object Accessed? +@cindex accessing volatiles +@cindex volatile read +@cindex volatile write +@cindex volatile access + +The C++ standard differs from the C standard in its treatment of +volatile objects. It fails to specify what constitutes a volatile +access, except to say that C++ should behave in a similar manner to C +with respect to volatiles, where possible. However, the different +lvalueness of expressions between C and C++ complicate the behavior. +G++ behaves the same as GCC for volatile access, @xref{C +Extensions,,Volatiles}, for a description of GCC's behavior. + +The C and C++ language specifications differ when an object is +accessed in a void context: + +@smallexample +volatile int *src = @var{somevalue}; +*src; +@end smallexample + +The C++ standard specifies that such expressions do not undergo lvalue +to rvalue conversion, and that the type of the dereferenced object may +be incomplete. The C++ standard does not specify explicitly that it +is lvalue to rvalue conversion which is responsible for causing an +access. There is reason to believe that it is, because otherwise +certain simple expressions become undefined. However, because it +would surprise most programmers, G++ treats dereferencing a pointer to +volatile object of complete type as GCC would do for an equivalent +type in C@. When the object has incomplete type, G++ issues a +warning; if you wish to force an error, you must force a conversion to +rvalue with, for instance, a static cast. + +When using a reference to volatile, G++ does not treat equivalent +expressions as accesses to volatiles, but instead issues a warning that +no volatile is accessed. The rationale for this is that otherwise it +becomes difficult to determine where volatile access occur, and not +possible to ignore the return value from functions returning volatile +references. Again, if you wish to force a read, cast the reference to +an rvalue. + +G++ implements the same behavior as GCC does when assigning to a +volatile object -- there is no reread of the assigned-to object, the +assigned rvalue is reused. Note that in C++ assignment expressions +are lvalues, and if used as an lvalue, the volatile object will be +referred to. For instance, @var{vref} will refer to @var{vobj}, as +expected, in the following example: + +@smallexample +volatile int vobj; +volatile int &vref = vobj = @var{something}; +@end smallexample + +@node Restricted Pointers +@section Restricting Pointer Aliasing +@cindex restricted pointers +@cindex restricted references +@cindex restricted this pointer + +As with the C front end, G++ understands the C99 feature of restricted pointers, +specified with the @code{__restrict__}, or @code{__restrict} type +qualifier. Because you cannot compile C++ by specifying the @option{-std=c99} +language flag, @code{restrict} is not a keyword in C++. + +In addition to allowing restricted pointers, you can specify restricted +references, which indicate that the reference is not aliased in the local +context. + +@smallexample +void fn (int *__restrict__ rptr, int &__restrict__ rref) +@{ + /* @r{@dots{}} */ +@} +@end smallexample + +@noindent +In the body of @code{fn}, @var{rptr} points to an unaliased integer and +@var{rref} refers to a (different) unaliased integer. + +You may also specify whether a member function's @var{this} pointer is +unaliased by using @code{__restrict__} as a member function qualifier. + +@smallexample +void T::fn () __restrict__ +@{ + /* @r{@dots{}} */ +@} +@end smallexample + +@noindent +Within the body of @code{T::fn}, @var{this} will have the effective +definition @code{T *__restrict__ const this}. Notice that the +interpretation of a @code{__restrict__} member function qualifier is +different to that of @code{const} or @code{volatile} qualifier, in that it +is applied to the pointer rather than the object. This is consistent with +other compilers which implement restricted pointers. + +As with all outermost parameter qualifiers, @code{__restrict__} is +ignored in function definition matching. This means you only need to +specify @code{__restrict__} in a function definition, rather than +in a function prototype as well. + +@node Vague Linkage +@section Vague Linkage +@cindex vague linkage + +There are several constructs in C++ which require space in the object +file but are not clearly tied to a single translation unit. We say that +these constructs have ``vague linkage''. Typically such constructs are +emitted wherever they are needed, though sometimes we can be more +clever. + +@table @asis +@item Inline Functions +Inline functions are typically defined in a header file which can be +included in many different compilations. Hopefully they can usually be +inlined, but sometimes an out-of-line copy is necessary, if the address +of the function is taken or if inlining fails. In general, we emit an +out-of-line copy in all translation units where one is needed. As an +exception, we only emit inline virtual functions with the vtable, since +it will always require a copy. + +Local static variables and string constants used in an inline function +are also considered to have vague linkage, since they must be shared +between all inlined and out-of-line instances of the function. + +@item VTables +@cindex vtable +C++ virtual functions are implemented in most compilers using a lookup +table, known as a vtable. The vtable contains pointers to the virtual +functions provided by a class, and each object of the class contains a +pointer to its vtable (or vtables, in some multiple-inheritance +situations). If the class declares any non-inline, non-pure virtual +functions, the first one is chosen as the ``key method'' for the class, +and the vtable is only emitted in the translation unit where the key +method is defined. + +@emph{Note:} If the chosen key method is later defined as inline, the +vtable will still be emitted in every translation unit which defines it. +Make sure that any inline virtuals are declared inline in the class +body, even if they are not defined there. + +@item @code{type_info} objects +@cindex @code{type_info} +@cindex RTTI +C++ requires information about types to be written out in order to +implement @samp{dynamic_cast}, @samp{typeid} and exception handling. +For polymorphic classes (classes with virtual functions), the @samp{type_info} +object is written out along with the vtable so that @samp{dynamic_cast} +can determine the dynamic type of a class object at runtime. For all +other types, we write out the @samp{type_info} object when it is used: when +applying @samp{typeid} to an expression, throwing an object, or +referring to a type in a catch clause or exception specification. + +@item Template Instantiations +Most everything in this section also applies to template instantiations, +but there are other options as well. +@xref{Template Instantiation,,Where's the Template?}. + +@end table + +When used with GNU ld version 2.8 or later on an ELF system such as +GNU/Linux or Solaris 2, or on Microsoft Windows, duplicate copies of +these constructs will be discarded at link time. This is known as +COMDAT support. + +On targets that don't support COMDAT, but do support weak symbols, GCC +will use them. This way one copy will override all the others, but +the unused copies will still take up space in the executable. + +For targets which do not support either COMDAT or weak symbols, +most entities with vague linkage will be emitted as local symbols to +avoid duplicate definition errors from the linker. This will not happen +for local statics in inlines, however, as having multiple copies will +almost certainly break things. + +@xref{C++ Interface,,Declarations and Definitions in One Header}, for +another way to control placement of these constructs. + +@node C++ Interface +@section #pragma interface and implementation + +@cindex interface and implementation headers, C++ +@cindex C++ interface and implementation headers +@cindex pragmas, interface and implementation + +@code{#pragma interface} and @code{#pragma implementation} provide the +user with a way of explicitly directing the compiler to emit entities +with vague linkage (and debugging information) in a particular +translation unit. + +@emph{Note:} As of GCC 2.7.2, these @code{#pragma}s are not useful in +most cases, because of COMDAT support and the ``key method'' heuristic +mentioned in @ref{Vague Linkage}. Using them can actually cause your +program to grow due to unnecessary out-of-line copies of inline +functions. Currently (3.4) the only benefit of these +@code{#pragma}s is reduced duplication of debugging information, and +that should be addressed soon on DWARF 2 targets with the use of +COMDAT groups. + +@table @code +@item #pragma interface +@itemx #pragma interface "@var{subdir}/@var{objects}.h" +@kindex #pragma interface +Use this directive in @emph{header files} that define object classes, to save +space in most of the object files that use those classes. Normally, +local copies of certain information (backup copies of inline member +functions, debugging information, and the internal tables that implement +virtual functions) must be kept in each object file that includes class +definitions. You can use this pragma to avoid such duplication. When a +header file containing @samp{#pragma interface} is included in a +compilation, this auxiliary information will not be generated (unless +the main input source file itself uses @samp{#pragma implementation}). +Instead, the object files will contain references to be resolved at link +time. + +The second form of this directive is useful for the case where you have +multiple headers with the same name in different directories. If you +use this form, you must specify the same string to @samp{#pragma +implementation}. + +@item #pragma implementation +@itemx #pragma implementation "@var{objects}.h" +@kindex #pragma implementation +Use this pragma in a @emph{main input file}, when you want full output from +included header files to be generated (and made globally visible). The +included header file, in turn, should use @samp{#pragma interface}. +Backup copies of inline member functions, debugging information, and the +internal tables used to implement virtual functions are all generated in +implementation files. + +@cindex implied @code{#pragma implementation} +@cindex @code{#pragma implementation}, implied +@cindex naming convention, implementation headers +If you use @samp{#pragma implementation} with no argument, it applies to +an include file with the same basename@footnote{A file's @dfn{basename} +was the name stripped of all leading path information and of trailing +suffixes, such as @samp{.h} or @samp{.C} or @samp{.cc}.} as your source +file. For example, in @file{allclass.cc}, giving just +@samp{#pragma implementation} +by itself is equivalent to @samp{#pragma implementation "allclass.h"}. + +In versions of GNU C++ prior to 2.6.0 @file{allclass.h} was treated as +an implementation file whenever you would include it from +@file{allclass.cc} even if you never specified @samp{#pragma +implementation}. This was deemed to be more trouble than it was worth, +however, and disabled. + +Use the string argument if you want a single implementation file to +include code from multiple header files. (You must also use +@samp{#include} to include the header file; @samp{#pragma +implementation} only specifies how to use the file---it doesn't actually +include it.) + +There is no way to split up the contents of a single header file into +multiple implementation files. +@end table + +@cindex inlining and C++ pragmas +@cindex C++ pragmas, effect on inlining +@cindex pragmas in C++, effect on inlining +@samp{#pragma implementation} and @samp{#pragma interface} also have an +effect on function inlining. + +If you define a class in a header file marked with @samp{#pragma +interface}, the effect on an inline function defined in that class is +similar to an explicit @code{extern} declaration---the compiler emits +no code at all to define an independent version of the function. Its +definition is used only for inlining with its callers. + +@opindex fno-implement-inlines +Conversely, when you include the same header file in a main source file +that declares it as @samp{#pragma implementation}, the compiler emits +code for the function itself; this defines a version of the function +that can be found via pointers (or by callers compiled without +inlining). If all calls to the function can be inlined, you can avoid +emitting the function by compiling with @option{-fno-implement-inlines}. +If any calls were not inlined, you will get linker errors. + +@node Template Instantiation +@section Where's the Template? +@cindex template instantiation + +C++ templates are the first language feature to require more +intelligence from the environment than one usually finds on a UNIX +system. Somehow the compiler and linker have to make sure that each +template instance occurs exactly once in the executable if it is needed, +and not at all otherwise. There are two basic approaches to this +problem, which are referred to as the Borland model and the Cfront model. + +@table @asis +@item Borland model +Borland C++ solved the template instantiation problem by adding the code +equivalent of common blocks to their linker; the compiler emits template +instances in each translation unit that uses them, and the linker +collapses them together. The advantage of this model is that the linker +only has to consider the object files themselves; there is no external +complexity to worry about. This disadvantage is that compilation time +is increased because the template code is being compiled repeatedly. +Code written for this model tends to include definitions of all +templates in the header file, since they must be seen to be +instantiated. + +@item Cfront model +The AT&T C++ translator, Cfront, solved the template instantiation +problem by creating the notion of a template repository, an +automatically maintained place where template instances are stored. A +more modern version of the repository works as follows: As individual +object files are built, the compiler places any template definitions and +instantiations encountered in the repository. At link time, the link +wrapper adds in the objects in the repository and compiles any needed +instances that were not previously emitted. The advantages of this +model are more optimal compilation speed and the ability to use the +system linker; to implement the Borland model a compiler vendor also +needs to replace the linker. The disadvantages are vastly increased +complexity, and thus potential for error; for some code this can be +just as transparent, but in practice it can been very difficult to build +multiple programs in one directory and one program in multiple +directories. Code written for this model tends to separate definitions +of non-inline member templates into a separate file, which should be +compiled separately. +@end table + +When used with GNU ld version 2.8 or later on an ELF system such as +GNU/Linux or Solaris 2, or on Microsoft Windows, G++ supports the +Borland model. On other systems, G++ implements neither automatic +model. + +A future version of G++ will support a hybrid model whereby the compiler +will emit any instantiations for which the template definition is +included in the compile, and store template definitions and +instantiation context information into the object file for the rest. +The link wrapper will extract that information as necessary and invoke +the compiler to produce the remaining instantiations. The linker will +then combine duplicate instantiations. + +In the mean time, you have the following options for dealing with +template instantiations: + +@enumerate +@item +@opindex frepo +Compile your template-using code with @option{-frepo}. The compiler will +generate files with the extension @samp{.rpo} listing all of the +template instantiations used in the corresponding object files which +could be instantiated there; the link wrapper, @samp{collect2}, will +then update the @samp{.rpo} files to tell the compiler where to place +those instantiations and rebuild any affected object files. The +link-time overhead is negligible after the first pass, as the compiler +will continue to place the instantiations in the same files. + +This is your best option for application code written for the Borland +model, as it will just work. Code written for the Cfront model will +need to be modified so that the template definitions are available at +one or more points of instantiation; usually this is as simple as adding +@code{#include <tmethods.cc>} to the end of each template header. + +For library code, if you want the library to provide all of the template +instantiations it needs, just try to link all of its object files +together; the link will fail, but cause the instantiations to be +generated as a side effect. Be warned, however, that this may cause +conflicts if multiple libraries try to provide the same instantiations. +For greater control, use explicit instantiation as described in the next +option. + +@item +@opindex fno-implicit-templates +Compile your code with @option{-fno-implicit-templates} to disable the +implicit generation of template instances, and explicitly instantiate +all the ones you use. This approach requires more knowledge of exactly +which instances you need than do the others, but it's less +mysterious and allows greater control. You can scatter the explicit +instantiations throughout your program, perhaps putting them in the +translation units where the instances are used or the translation units +that define the templates themselves; you can put all of the explicit +instantiations you need into one big file; or you can create small files +like + +@smallexample +#include "Foo.h" +#include "Foo.cc" + +template class Foo<int>; +template ostream& operator << + (ostream&, const Foo<int>&); +@end smallexample + +for each of the instances you need, and create a template instantiation +library from those. + +If you are using Cfront-model code, you can probably get away with not +using @option{-fno-implicit-templates} when compiling files that don't +@samp{#include} the member template definitions. + +If you use one big file to do the instantiations, you may want to +compile it without @option{-fno-implicit-templates} so you get all of the +instances required by your explicit instantiations (but not by any +other files) without having to specify them as well. + +G++ has extended the template instantiation syntax given in the ISO +standard to allow forward declaration of explicit instantiations +(with @code{extern}), instantiation of the compiler support data for a +template class (i.e.@: the vtable) without instantiating any of its +members (with @code{inline}), and instantiation of only the static data +members of a template class, without the support data or member +functions (with (@code{static}): + +@smallexample +extern template int max (int, int); +inline template class Foo<int>; +static template class Foo<int>; +@end smallexample + +@item +Do nothing. Pretend G++ does implement automatic instantiation +management. Code written for the Borland model will work fine, but +each translation unit will contain instances of each of the templates it +uses. In a large program, this can lead to an unacceptable amount of code +duplication. +@end enumerate + +@node Bound member functions +@section Extracting the function pointer from a bound pointer to member function +@cindex pmf +@cindex pointer to member function +@cindex bound pointer to member function + +In C++, pointer to member functions (PMFs) are implemented using a wide +pointer of sorts to handle all the possible call mechanisms; the PMF +needs to store information about how to adjust the @samp{this} pointer, +and if the function pointed to is virtual, where to find the vtable, and +where in the vtable to look for the member function. If you are using +PMFs in an inner loop, you should really reconsider that decision. If +that is not an option, you can extract the pointer to the function that +would be called for a given object/PMF pair and call it directly inside +the inner loop, to save a bit of time. + +Note that you will still be paying the penalty for the call through a +function pointer; on most modern architectures, such a call defeats the +branch prediction features of the CPU@. This is also true of normal +virtual function calls. + +The syntax for this extension is + +@smallexample +extern A a; +extern int (A::*fp)(); +typedef int (*fptr)(A *); + +fptr p = (fptr)(a.*fp); +@end smallexample + +For PMF constants (i.e.@: expressions of the form @samp{&Klasse::Member}), +no object is needed to obtain the address of the function. They can be +converted to function pointers directly: + +@smallexample +fptr p1 = (fptr)(&A::foo); +@end smallexample + +@opindex Wno-pmf-conversions +You must specify @option{-Wno-pmf-conversions} to use this extension. + +@node C++ Attributes +@section C++-Specific Variable, Function, and Type Attributes + +Some attributes only make sense for C++ programs. + +@table @code +@item init_priority (@var{priority}) +@cindex @code{init_priority} attribute + + +In Standard C++, objects defined at namespace scope are guaranteed to be +initialized in an order in strict accordance with that of their definitions +@emph{in a given translation unit}. No guarantee is made for initializations +across translation units. However, GNU C++ allows users to control the +order of initialization of objects defined at namespace scope with the +@code{init_priority} attribute by specifying a relative @var{priority}, +a constant integral expression currently bounded between 101 and 65535 +inclusive. Lower numbers indicate a higher priority. + +In the following example, @code{A} would normally be created before +@code{B}, but the @code{init_priority} attribute has reversed that order: + +@smallexample +Some_Class A __attribute__ ((init_priority (2000))); +Some_Class B __attribute__ ((init_priority (543))); +@end smallexample + +@noindent +Note that the particular values of @var{priority} do not matter; only their +relative ordering. + +@item java_interface +@cindex @code{java_interface} attribute + +This type attribute informs C++ that the class is a Java interface. It may +only be applied to classes declared within an @code{extern "Java"} block. +Calls to methods declared in this interface will be dispatched using GCJ's +interface table mechanism, instead of regular virtual table dispatch. + +@end table + +See also @ref{Namespace Association}. + +@node Namespace Association +@section Namespace Association + +@strong{Caution:} The semantics of this extension are not fully +defined. Users should refrain from using this extension as its +semantics may change subtly over time. It is possible that this +extension will be removed in future versions of G++. + +A using-directive with @code{__attribute ((strong))} is stronger +than a normal using-directive in two ways: + +@itemize @bullet +@item +Templates from the used namespace can be specialized and explicitly +instantiated as though they were members of the using namespace. + +@item +The using namespace is considered an associated namespace of all +templates in the used namespace for purposes of argument-dependent +name lookup. +@end itemize + +The used namespace must be nested within the using namespace so that +normal unqualified lookup works properly. + +This is useful for composing a namespace transparently from +implementation namespaces. For example: + +@smallexample +namespace std @{ + namespace debug @{ + template <class T> struct A @{ @}; + @} + using namespace debug __attribute ((__strong__)); + template <> struct A<int> @{ @}; // @r{ok to specialize} + + template <class T> void f (A<T>); +@} + +int main() +@{ + f (std::A<float>()); // @r{lookup finds} std::f + f (std::A<int>()); +@} +@end smallexample + +@node Type Traits +@section Type Traits + +The C++ front-end implements syntactic extensions that allow to +determine at compile time various characteristics of a type (or of a +pair of types). + +@table @code +@item __has_nothrow_assign (type) +If @code{type} is const qualified or is a reference type then the trait is +false. Otherwise if @code{__has_trivial_assign (type)} is true then the trait +is true, else if @code{type} is a cv class or union type with copy assignment +operators that are known not to throw an exception then the trait is true, +else it is false. Requires: @code{type} shall be a complete type, +(possibly cv-qualified) @code{void}, or an array of unknown bound. + +@item __has_nothrow_copy (type) +If @code{__has_trivial_copy (type)} is true then the trait is true, else if +@code{type} is a cv class or union type with copy constructors that +are known not to throw an exception then the trait is true, else it is false. +Requires: @code{type} shall be a complete type, (possibly cv-qualified) +@code{void}, or an array of unknown bound. + +@item __has_nothrow_constructor (type) +If @code{__has_trivial_constructor (type)} is true then the trait is +true, else if @code{type} is a cv class or union type (or array +thereof) with a default constructor that is known not to throw an +exception then the trait is true, else it is false. Requires: +@code{type} shall be a complete type, (possibly cv-qualified) +@code{void}, or an array of unknown bound. + +@item __has_trivial_assign (type) +If @code{type} is const qualified or is a reference type then the trait is +false. Otherwise if @code{__is_pod (type)} is true then the trait is +true, else if @code{type} is a cv class or union type with a trivial +copy assignment ([class.copy]) then the trait is true, else it is +false. Requires: @code{type} shall be a complete type, (possibly +cv-qualified) @code{void}, or an array of unknown bound. + +@item __has_trivial_copy (type) +If @code{__is_pod (type)} is true or @code{type} is a reference type +then the trait is true, else if @code{type} is a cv class or union type +with a trivial copy constructor ([class.copy]) then the trait +is true, else it is false. Requires: @code{type} shall be a complete +type, (possibly cv-qualified) @code{void}, or an array of unknown bound. + +@item __has_trivial_constructor (type) +If @code{__is_pod (type)} is true then the trait is true, else if +@code{type} is a cv class or union type (or array thereof) with a +trivial default constructor ([class.ctor]) then the trait is true, +else it is false. Requires: @code{type} shall be a complete +type, (possibly cv-qualified) @code{void}, or an array of unknown bound. + +@item __has_trivial_destructor (type) +If @code{__is_pod (type)} is true or @code{type} is a reference type then +the trait is true, else if @code{type} is a cv class or union type (or +array thereof) with a trivial destructor ([class.dtor]) then the trait +is true, else it is false. Requires: @code{type} shall be a complete +type, (possibly cv-qualified) @code{void}, or an array of unknown bound. + +@item __has_virtual_destructor (type) +If @code{type} is a class type with a virtual destructor +([class.dtor]) then the trait is true, else it is false. Requires: +@code{type} shall be a complete type, (possibly cv-qualified) +@code{void}, or an array of unknown bound. + +@item __is_abstract (type) +If @code{type} is an abstract class ([class.abstract]) then the trait +is true, else it is false. Requires: @code{type} shall be a complete +type, (possibly cv-qualified) @code{void}, or an array of unknown bound. + +@item __is_base_of (base_type, derived_type) +If @code{base_type} is a base class of @code{derived_type} +([class.derived]) then the trait is true, otherwise it is false. +Top-level cv qualifications of @code{base_type} and +@code{derived_type} are ignored. For the purposes of this trait, a +class type is considered is own base. Requires: if @code{__is_class +(base_type)} and @code{__is_class (derived_type)} are true and +@code{base_type} and @code{derived_type} are not the same type +(disregarding cv-qualifiers), @code{derived_type} shall be a complete +type. Diagnostic is produced if this requirement is not met. + +@item __is_class (type) +If @code{type} is a cv class type, and not a union type +([basic.compound]) the trait is true, else it is false. + +@item __is_empty (type) +If @code{__is_class (type)} is false then the trait is false. +Otherwise @code{type} is considered empty if and only if: @code{type} +has no non-static data members, or all non-static data members, if +any, are bit-fields of length 0, and @code{type} has no virtual +members, and @code{type} has no virtual base classes, and @code{type} +has no base classes @code{base_type} for which +@code{__is_empty (base_type)} is false. Requires: @code{type} shall +be a complete type, (possibly cv-qualified) @code{void}, or an array +of unknown bound. + +@item __is_enum (type) +If @code{type} is a cv enumeration type ([basic.compound]) the trait is +true, else it is false. + +@item __is_literal_type (type) +If @code{type} is a literal type ([basic.types]) the trait is +true, else it is false. Requires: @code{type} shall be a complete type, +(possibly cv-qualified) @code{void}, or an array of unknown bound. + +@item __is_pod (type) +If @code{type} is a cv POD type ([basic.types]) then the trait is true, +else it is false. Requires: @code{type} shall be a complete type, +(possibly cv-qualified) @code{void}, or an array of unknown bound. + +@item __is_polymorphic (type) +If @code{type} is a polymorphic class ([class.virtual]) then the trait +is true, else it is false. Requires: @code{type} shall be a complete +type, (possibly cv-qualified) @code{void}, or an array of unknown bound. + +@item __is_standard_layout (type) +If @code{type} is a standard-layout type ([basic.types]) the trait is +true, else it is false. Requires: @code{type} shall be a complete +type, (possibly cv-qualified) @code{void}, or an array of unknown bound. + +@item __is_trivial (type) +If @code{type} is a trivial type ([basic.types]) the trait is +true, else it is false. Requires: @code{type} shall be a complete +type, (possibly cv-qualified) @code{void}, or an array of unknown bound. + +@item __is_union (type) +If @code{type} is a cv union type ([basic.compound]) the trait is +true, else it is false. + +@end table + +@node Java Exceptions +@section Java Exceptions + +The Java language uses a slightly different exception handling model +from C++. Normally, GNU C++ will automatically detect when you are +writing C++ code that uses Java exceptions, and handle them +appropriately. However, if C++ code only needs to execute destructors +when Java exceptions are thrown through it, GCC will guess incorrectly. +Sample problematic code is: + +@smallexample + struct S @{ ~S(); @}; + extern void bar(); // @r{is written in Java, and may throw exceptions} + void foo() + @{ + S s; + bar(); + @} +@end smallexample + +@noindent +The usual effect of an incorrect guess is a link failure, complaining of +a missing routine called @samp{__gxx_personality_v0}. + +You can inform the compiler that Java exceptions are to be used in a +translation unit, irrespective of what it might think, by writing +@samp{@w{#pragma GCC java_exceptions}} at the head of the file. This +@samp{#pragma} must appear before any functions that throw or catch +exceptions, or run destructors when exceptions are thrown through them. + +You cannot mix Java and C++ exceptions in the same translation unit. It +is believed to be safe to throw a C++ exception from one file through +another file compiled for the Java exception model, or vice versa, but +there may be bugs in this area. + +@node Deprecated Features +@section Deprecated Features + +In the past, the GNU C++ compiler was extended to experiment with new +features, at a time when the C++ language was still evolving. Now that +the C++ standard is complete, some of those features are superseded by +superior alternatives. Using the old features might cause a warning in +some cases that the feature will be dropped in the future. In other +cases, the feature might be gone already. + +While the list below is not exhaustive, it documents some of the options +that are now deprecated: + +@table @code +@item -fexternal-templates +@itemx -falt-external-templates +These are two of the many ways for G++ to implement template +instantiation. @xref{Template Instantiation}. The C++ standard clearly +defines how template definitions have to be organized across +implementation units. G++ has an implicit instantiation mechanism that +should work just fine for standard-conforming code. + +@item -fstrict-prototype +@itemx -fno-strict-prototype +Previously it was possible to use an empty prototype parameter list to +indicate an unspecified number of parameters (like C), rather than no +parameters, as C++ demands. This feature has been removed, except where +it is required for backwards compatibility. @xref{Backwards Compatibility}. +@end table + +G++ allows a virtual function returning @samp{void *} to be overridden +by one returning a different pointer type. This extension to the +covariant return type rules is now deprecated and will be removed from a +future version. + +The G++ minimum and maximum operators (@samp{<?} and @samp{>?}) and +their compound forms (@samp{<?=}) and @samp{>?=}) have been deprecated +and are now removed from G++. Code using these operators should be +modified to use @code{std::min} and @code{std::max} instead. + +The named return value extension has been deprecated, and is now +removed from G++. + +The use of initializer lists with new expressions has been deprecated, +and is now removed from G++. + +Floating and complex non-type template parameters have been deprecated, +and are now removed from G++. + +The implicit typename extension has been deprecated and is now +removed from G++. + +The use of default arguments in function pointers, function typedefs +and other places where they are not permitted by the standard is +deprecated and will be removed from a future version of G++. + +G++ allows floating-point literals to appear in integral constant expressions, +e.g. @samp{ enum E @{ e = int(2.2 * 3.7) @} } +This extension is deprecated and will be removed from a future version. + +G++ allows static data members of const floating-point type to be declared +with an initializer in a class definition. The standard only allows +initializers for static members of const integral types and const +enumeration types so this extension has been deprecated and will be removed +from a future version. + +@node Backwards Compatibility +@section Backwards Compatibility +@cindex Backwards Compatibility +@cindex ARM [Annotated C++ Reference Manual] + +Now that there is a definitive ISO standard C++, G++ has a specification +to adhere to. The C++ language evolved over time, and features that +used to be acceptable in previous drafts of the standard, such as the ARM +[Annotated C++ Reference Manual], are no longer accepted. In order to allow +compilation of C++ written to such drafts, G++ contains some backwards +compatibilities. @emph{All such backwards compatibility features are +liable to disappear in future versions of G++.} They should be considered +deprecated. @xref{Deprecated Features}. + +@table @code +@item For scope +If a variable is declared at for scope, it used to remain in scope until +the end of the scope which contained the for statement (rather than just +within the for scope). G++ retains this, but issues a warning, if such a +variable is accessed outside the for scope. + +@item Implicit C language +Old C system header files did not contain an @code{extern "C" @{@dots{}@}} +scope to set the language. On such systems, all header files are +implicitly scoped inside a C language scope. Also, an empty prototype +@code{()} will be treated as an unspecified number of arguments, rather +than no arguments, as C++ demands. +@end table |