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------------------------------------------------------------------------------
-- --
-- GNAT COMPILER COMPONENTS --
-- --
-- T T Y P E S --
-- --
-- S p e c --
-- --
-- Copyright (C) 1992-2009, Free Software Foundation, Inc. --
-- --
-- GNAT is free software; you can redistribute it and/or modify it under --
-- terms of the GNU General Public License as published by the Free Soft- --
-- ware Foundation; either version 3, or (at your option) any later ver- --
-- sion. GNAT is distributed in the hope that it will be useful, but WITH- --
-- OUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY --
-- or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License --
-- for more details. You should have received a copy of the GNU General --
-- Public License distributed with GNAT; see file COPYING3. If not, go to --
-- http://www.gnu.org/licenses for a complete copy of the license. --
-- --
-- GNAT was originally developed by the GNAT team at New York University. --
-- Extensive contributions were provided by Ada Core Technologies Inc. --
-- --
------------------------------------------------------------------------------
-- This package contains constants describing target properties
with Types; use Types;
with Get_Targ; use Get_Targ;
package Ttypes is
------------------------------
-- Host/Target Dependencies --
------------------------------
-- It is vital to maintain a clear distinction between properties of
-- types on the host and types on the target, since in the general
-- case of a cross-compiler these will be different.
-- This package and its companion Ttypef provide definitions of values
-- that describe the properties of the target types. All instances of
-- target dependencies, including the definitions of such packages as
-- Standard and System depend directly or indirectly on the definitions
-- in the Ttypes and Ttypef packages.
-- In the source of the compiler, references to attributes such as
-- Integer'Size will give information regarding the host types (i.e.
-- the types within the compiler itself). Such references are therefore
-- almost always suspicious (it is hard for example to see that the
-- code in the compiler should even be using type Integer very much,
-- and certainly this code should not depend on the size of Integer).
-- On the other hand, it is perfectly reasonable for the compiler to
-- require access to the size of type Integer for the target machine,
-- e.g. in constructing the internal representation of package Standard.
-- For this purpose, instead of referencing the attribute Integer'Size,
-- a reference to Ttypes.Standard_Integer_Size will provide the needed
-- value for the target type.
-- Two approaches are used for handling target dependent values in the
-- standard library packages. Package Standard is handled specially,
-- being constructed internally (by package Stand). Target dependent
-- values needed in Stand are obtained by direct reference to Ttypes
-- and Ttypef.
-- For package System, the required constant values are obtained by
-- referencing appropriate attributes. Ada 95 already defines most of
-- the required attributes, and GNAT specific attributes have been
-- defined to cover the remaining cases (such as Storage_Unit). The
-- evaluation of these attributes obtains the required target dependent
-- values from Ttypes and Ttypef. The additional attributes that have
-- been added to GNAT (Address_Size, Storage_Unit, Word_Size, Max_Priority,
-- and Max_Interrupt_Priority) are for almost all purposes redundant with
-- respect to the corresponding references to System constants. For example
-- in a program, System.Address_Size and Standard'Address_Size yield the
-- same value. The critical use of the attribute is in writing the System
-- declaration of Address_Size which of course cannot refer to itself. By
-- this means we achieve complete target independence in the source code
-- of package System, i.e. there is only one copy of the source of System
-- for all targets.
-- Note that during compilation there are two versions of package System
-- around. The version that is directly with'ed by compiler packages
-- contains host-dependent definitions, which is what is needed in that
-- case (for example, System.Storage_Unit referenced in the source of the
-- compiler refers to the storage unit of the host, not the target). This
-- means that, like attribute references, any references to constants in
-- package System in the compiler code are suspicious, since it is strange
-- for the compiler to have such host dependencies. If the compiler needs
-- to access the target dependent values of such quantities as Storage_Unit
-- then it should reference the constants in this package (Ttypes), rather
-- than referencing System.Storage_Unit, or Standard'Storage_Unit, both of
-- which would yield the host value.
---------------------------------------------------
-- Target-Dependent Values for Types in Standard --
---------------------------------------------------
-- Note: GNAT always supplies all the following integer and float types,
-- but depending on the machine, some of the types may be identical. For
-- example, on some machines, Short_Float may be the same as Float, and
-- Long_Long_Float may be the same as Long_Float.
Standard_Short_Short_Integer_Size : constant Pos := Get_Char_Size;
Standard_Short_Short_Integer_Width : constant Pos :=
Width_From_Size (Standard_Short_Short_Integer_Size);
Standard_Short_Integer_Size : constant Pos := Get_Short_Size;
Standard_Short_Integer_Width : constant Pos :=
Width_From_Size (Standard_Short_Integer_Size);
Standard_Integer_Size : constant Pos := Get_Int_Size;
Standard_Integer_Width : constant Pos :=
Width_From_Size (Standard_Integer_Size);
Standard_Long_Integer_Size : constant Pos := Get_Long_Size;
Standard_Long_Integer_Width : constant Pos :=
Width_From_Size (Standard_Long_Integer_Size);
Standard_Long_Long_Integer_Size : constant Pos := Get_Long_Long_Size;
Standard_Long_Long_Integer_Width : constant Pos :=
Width_From_Size (Standard_Long_Long_Integer_Size);
Standard_Short_Float_Size : constant Pos := Get_Float_Size;
Standard_Short_Float_Digits : constant Pos :=
Digits_From_Size (Standard_Short_Float_Size);
Standard_Float_Size : constant Pos := Get_Float_Size;
Standard_Float_Digits : constant Pos :=
Digits_From_Size (Standard_Float_Size);
Standard_Long_Float_Size : constant Pos := Get_Double_Size;
Standard_Long_Float_Digits : constant Pos :=
Digits_From_Size (Standard_Long_Float_Size);
Standard_Long_Long_Float_Size : constant Pos := Get_Long_Double_Size;
Standard_Long_Long_Float_Digits : constant Pos :=
Digits_From_Size (Standard_Long_Long_Float_Size);
Standard_Character_Size : constant Pos := Get_Char_Size;
Standard_Wide_Character_Size : constant Pos := 16;
Standard_Wide_Wide_Character_Size : constant Pos := 32;
-- Standard wide character sizes
-- Note: there is no specific control over the representation of
-- enumeration types. The convention used is that if an enumeration
-- type has fewer than 2**(Character'Size) elements, then the size
-- used is Character'Size, otherwise Integer'Size is used.
-- Similarly, the size of fixed-point types depends on the size of the
-- corresponding integer type, which is the smallest predefined integer
-- type capable of representing the required range of values.
-------------------------------------------------
-- Target-Dependent Values for Types in System --
-------------------------------------------------
System_Address_Size : constant Pos := Get_Pointer_Size;
-- System.Address'Size (also size of all thin pointers)
System_Max_Binary_Modulus_Power : constant Pos :=
Standard_Long_Long_Integer_Size;
System_Max_Nonbinary_Modulus_Power : constant Pos := Standard_Integer_Size;
System_Storage_Unit : constant Pos := Get_Bits_Per_Unit;
System_Word_Size : constant Pos := Get_Bits_Per_Word;
System_Tick_Nanoseconds : constant Pos := 1_000_000_000;
-- Value of System.Tick in nanoseconds. At the moment, this is a fixed
-- constant (with value of 1.0 seconds), but later we should add this
-- value to the GCC configuration file so that its value can be made
-- configuration dependent.
-----------------------------------------------------
-- Target-Dependent Values for Types in Interfaces --
-----------------------------------------------------
Interfaces_Wchar_T_Size : constant Pos := Get_Wchar_T_Size;
----------------------------------------
-- Other Target-Dependent Definitions --
----------------------------------------
Maximum_Alignment : constant Pos := Get_Maximum_Alignment;
-- The maximum alignment, in storage units, that an object or
-- type may require on the target machine.
Max_Unaligned_Field : constant Pos := Get_Max_Unaligned_Field;
-- The maximum supported size in bits for a field that is not aligned
-- on a storage unit boundary.
Bytes_Big_Endian : Boolean := Get_Bytes_BE /= 0;
-- Important note: for Ada purposes, the important setting is the bytes
-- endianness (Bytes_Big_Endian), not the bits value (Bits_Big_Endian).
-- This is because Ada bit addressing must be compatible with the byte
-- ordering (otherwise we would end up with non-contiguous fields). It
-- is rare for the two to be different, but if they are, Bits_Big_Endian
-- is relevant only for the generation of instructions with bit numbers,
-- and thus relevant only to the back end. Note that this is a variable
-- rather than a constant, since it can be modified (flipped) by -gnatd8.
Target_Strict_Alignment : Boolean := Get_Strict_Alignment /= 0;
-- True if instructions will fail if data is misaligned
Target_Double_Float_Alignment : Nat := Get_Double_Float_Alignment;
-- The default alignment of "double" floating-point types, i.e. floating
-- point types whose size is equal to 64 bits, or 0 if this alignment is
-- not specifically capped.
Target_Double_Scalar_Alignment : Nat := Get_Double_Scalar_Alignment;
-- The default alignment of "double" or larger scalar types, i.e. scalar
-- types whose size is greater or equal to 64 bits, or 0 if this alignment
-- is not specifically capped.
end Ttypes;
|
