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authorupstream source tree <ports@midipix.org>2015-03-15 20:14:05 -0400
committerupstream source tree <ports@midipix.org>2015-03-15 20:14:05 -0400
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tree976dc5ab7fddf506dadce60ae936f43f58787092 /gcc/gcse.c
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+/* Global common subexpression elimination/Partial redundancy elimination
+ and global constant/copy propagation for GNU compiler.
+ Copyright (C) 1997, 1998, 1999, 2000, 2001, 2002, 2003, 2004, 2005,
+ 2006, 2007, 2008, 2009, 2010, 2011 Free Software Foundation, Inc.
+
+This file is part of GCC.
+
+GCC is free software; you can redistribute it and/or modify it under
+the terms of the GNU General Public License as published by the Free
+Software Foundation; either version 3, or (at your option) any later
+version.
+
+GCC is distributed in the hope that it will be useful, but WITHOUT 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
+along with GCC; see the file COPYING3. If not see
+<http://www.gnu.org/licenses/>. */
+
+/* TODO
+ - reordering of memory allocation and freeing to be more space efficient
+ - do rough calc of how many regs are needed in each block, and a rough
+ calc of how many regs are available in each class and use that to
+ throttle back the code in cases where RTX_COST is minimal.
+ - a store to the same address as a load does not kill the load if the
+ source of the store is also the destination of the load. Handling this
+ allows more load motion, particularly out of loops.
+
+*/
+
+/* References searched while implementing this.
+
+ Compilers Principles, Techniques and Tools
+ Aho, Sethi, Ullman
+ Addison-Wesley, 1988
+
+ Global Optimization by Suppression of Partial Redundancies
+ E. Morel, C. Renvoise
+ communications of the acm, Vol. 22, Num. 2, Feb. 1979
+
+ A Portable Machine-Independent Global Optimizer - Design and Measurements
+ Frederick Chow
+ Stanford Ph.D. thesis, Dec. 1983
+
+ A Fast Algorithm for Code Movement Optimization
+ D.M. Dhamdhere
+ SIGPLAN Notices, Vol. 23, Num. 10, Oct. 1988
+
+ A Solution to a Problem with Morel and Renvoise's
+ Global Optimization by Suppression of Partial Redundancies
+ K-H Drechsler, M.P. Stadel
+ ACM TOPLAS, Vol. 10, Num. 4, Oct. 1988
+
+ Practical Adaptation of the Global Optimization
+ Algorithm of Morel and Renvoise
+ D.M. Dhamdhere
+ ACM TOPLAS, Vol. 13, Num. 2. Apr. 1991
+
+ Efficiently Computing Static Single Assignment Form and the Control
+ Dependence Graph
+ R. Cytron, J. Ferrante, B.K. Rosen, M.N. Wegman, and F.K. Zadeck
+ ACM TOPLAS, Vol. 13, Num. 4, Oct. 1991
+
+ Lazy Code Motion
+ J. Knoop, O. Ruthing, B. Steffen
+ ACM SIGPLAN Notices Vol. 27, Num. 7, Jul. 1992, '92 Conference on PLDI
+
+ What's In a Region? Or Computing Control Dependence Regions in Near-Linear
+ Time for Reducible Flow Control
+ Thomas Ball
+ ACM Letters on Programming Languages and Systems,
+ Vol. 2, Num. 1-4, Mar-Dec 1993
+
+ An Efficient Representation for Sparse Sets
+ Preston Briggs, Linda Torczon
+ ACM Letters on Programming Languages and Systems,
+ Vol. 2, Num. 1-4, Mar-Dec 1993
+
+ A Variation of Knoop, Ruthing, and Steffen's Lazy Code Motion
+ K-H Drechsler, M.P. Stadel
+ ACM SIGPLAN Notices, Vol. 28, Num. 5, May 1993
+
+ Partial Dead Code Elimination
+ J. Knoop, O. Ruthing, B. Steffen
+ ACM SIGPLAN Notices, Vol. 29, Num. 6, Jun. 1994
+
+ Effective Partial Redundancy Elimination
+ P. Briggs, K.D. Cooper
+ ACM SIGPLAN Notices, Vol. 29, Num. 6, Jun. 1994
+
+ The Program Structure Tree: Computing Control Regions in Linear Time
+ R. Johnson, D. Pearson, K. Pingali
+ ACM SIGPLAN Notices, Vol. 29, Num. 6, Jun. 1994
+
+ Optimal Code Motion: Theory and Practice
+ J. Knoop, O. Ruthing, B. Steffen
+ ACM TOPLAS, Vol. 16, Num. 4, Jul. 1994
+
+ The power of assignment motion
+ J. Knoop, O. Ruthing, B. Steffen
+ ACM SIGPLAN Notices Vol. 30, Num. 6, Jun. 1995, '95 Conference on PLDI
+
+ Global code motion / global value numbering
+ C. Click
+ ACM SIGPLAN Notices Vol. 30, Num. 6, Jun. 1995, '95 Conference on PLDI
+
+ Value Driven Redundancy Elimination
+ L.T. Simpson
+ Rice University Ph.D. thesis, Apr. 1996
+
+ Value Numbering
+ L.T. Simpson
+ Massively Scalar Compiler Project, Rice University, Sep. 1996
+
+ High Performance Compilers for Parallel Computing
+ Michael Wolfe
+ Addison-Wesley, 1996
+
+ Advanced Compiler Design and Implementation
+ Steven Muchnick
+ Morgan Kaufmann, 1997
+
+ Building an Optimizing Compiler
+ Robert Morgan
+ Digital Press, 1998
+
+ People wishing to speed up the code here should read:
+ Elimination Algorithms for Data Flow Analysis
+ B.G. Ryder, M.C. Paull
+ ACM Computing Surveys, Vol. 18, Num. 3, Sep. 1986
+
+ How to Analyze Large Programs Efficiently and Informatively
+ D.M. Dhamdhere, B.K. Rosen, F.K. Zadeck
+ ACM SIGPLAN Notices Vol. 27, Num. 7, Jul. 1992, '92 Conference on PLDI
+
+ People wishing to do something different can find various possibilities
+ in the above papers and elsewhere.
+*/
+
+#include "config.h"
+#include "system.h"
+#include "coretypes.h"
+#include "tm.h"
+#include "diagnostic-core.h"
+#include "toplev.h"
+
+#include "rtl.h"
+#include "tree.h"
+#include "tm_p.h"
+#include "regs.h"
+#include "hard-reg-set.h"
+#include "flags.h"
+#include "insn-config.h"
+#include "recog.h"
+#include "basic-block.h"
+#include "output.h"
+#include "function.h"
+#include "expr.h"
+#include "except.h"
+#include "ggc.h"
+#include "params.h"
+#include "cselib.h"
+#include "intl.h"
+#include "obstack.h"
+#include "timevar.h"
+#include "tree-pass.h"
+#include "hashtab.h"
+#include "df.h"
+#include "dbgcnt.h"
+#include "target.h"
+#include "gcse.h"
+
+/* We support GCSE via Partial Redundancy Elimination. PRE optimizations
+ are a superset of those done by classic GCSE.
+
+ We perform the following steps:
+
+ 1) Compute table of places where registers are set.
+
+ 2) Perform copy/constant propagation.
+
+ 3) Perform global cse using lazy code motion if not optimizing
+ for size, or code hoisting if we are.
+
+ 4) Perform another pass of copy/constant propagation. Try to bypass
+ conditional jumps if the condition can be computed from a value of
+ an incoming edge.
+
+ Two passes of copy/constant propagation are done because the first one
+ enables more GCSE and the second one helps to clean up the copies that
+ GCSE creates. This is needed more for PRE than for Classic because Classic
+ GCSE will try to use an existing register containing the common
+ subexpression rather than create a new one. This is harder to do for PRE
+ because of the code motion (which Classic GCSE doesn't do).
+
+ Expressions we are interested in GCSE-ing are of the form
+ (set (pseudo-reg) (expression)).
+ Function want_to_gcse_p says what these are.
+
+ In addition, expressions in REG_EQUAL notes are candidates for GCSE-ing.
+ This allows PRE to hoist expressions that are expressed in multiple insns,
+ such as complex address calculations (e.g. for PIC code, or loads with a
+ high part and a low part).
+
+ PRE handles moving invariant expressions out of loops (by treating them as
+ partially redundant).
+
+ **********************
+
+ We used to support multiple passes but there are diminishing returns in
+ doing so. The first pass usually makes 90% of the changes that are doable.
+ A second pass can make a few more changes made possible by the first pass.
+ Experiments show any further passes don't make enough changes to justify
+ the expense.
+
+ A study of spec92 using an unlimited number of passes:
+ [1 pass] = 1208 substitutions, [2] = 577, [3] = 202, [4] = 192, [5] = 83,
+ [6] = 34, [7] = 17, [8] = 9, [9] = 4, [10] = 4, [11] = 2,
+ [12] = 2, [13] = 1, [15] = 1, [16] = 2, [41] = 1
+
+ It was found doing copy propagation between each pass enables further
+ substitutions.
+
+ This study was done before expressions in REG_EQUAL notes were added as
+ candidate expressions for optimization, and before the GIMPLE optimizers
+ were added. Probably, multiple passes is even less efficient now than
+ at the time when the study was conducted.
+
+ PRE is quite expensive in complicated functions because the DFA can take
+ a while to converge. Hence we only perform one pass.
+
+ **********************
+
+ The steps for PRE are:
+
+ 1) Build the hash table of expressions we wish to GCSE (expr_hash_table).
+
+ 2) Perform the data flow analysis for PRE.
+
+ 3) Delete the redundant instructions
+
+ 4) Insert the required copies [if any] that make the partially
+ redundant instructions fully redundant.
+
+ 5) For other reaching expressions, insert an instruction to copy the value
+ to a newly created pseudo that will reach the redundant instruction.
+
+ The deletion is done first so that when we do insertions we
+ know which pseudo reg to use.
+
+ Various papers have argued that PRE DFA is expensive (O(n^2)) and others
+ argue it is not. The number of iterations for the algorithm to converge
+ is typically 2-4 so I don't view it as that expensive (relatively speaking).
+
+ PRE GCSE depends heavily on the second CPROP pass to clean up the copies
+ we create. To make an expression reach the place where it's redundant,
+ the result of the expression is copied to a new register, and the redundant
+ expression is deleted by replacing it with this new register. Classic GCSE
+ doesn't have this problem as much as it computes the reaching defs of
+ each register in each block and thus can try to use an existing
+ register. */
+
+/* GCSE global vars. */
+
+struct target_gcse default_target_gcse;
+#if SWITCHABLE_TARGET
+struct target_gcse *this_target_gcse = &default_target_gcse;
+#endif
+
+/* Set to non-zero if CSE should run after all GCSE optimizations are done. */
+int flag_rerun_cse_after_global_opts;
+
+/* An obstack for our working variables. */
+static struct obstack gcse_obstack;
+
+struct reg_use {rtx reg_rtx; };
+
+/* Hash table of expressions. */
+
+struct expr
+{
+ /* The expression (SET_SRC for expressions, PATTERN for assignments). */
+ rtx expr;
+ /* Index in the available expression bitmaps. */
+ int bitmap_index;
+ /* Next entry with the same hash. */
+ struct expr *next_same_hash;
+ /* List of anticipatable occurrences in basic blocks in the function.
+ An "anticipatable occurrence" is one that is the first occurrence in the
+ basic block, the operands are not modified in the basic block prior
+ to the occurrence and the output is not used between the start of
+ the block and the occurrence. */
+ struct occr *antic_occr;
+ /* List of available occurrence in basic blocks in the function.
+ An "available occurrence" is one that is the last occurrence in the
+ basic block and the operands are not modified by following statements in
+ the basic block [including this insn]. */
+ struct occr *avail_occr;
+ /* Non-null if the computation is PRE redundant.
+ The value is the newly created pseudo-reg to record a copy of the
+ expression in all the places that reach the redundant copy. */
+ rtx reaching_reg;
+ /* Maximum distance in instructions this expression can travel.
+ We avoid moving simple expressions for more than a few instructions
+ to keep register pressure under control.
+ A value of "0" removes restrictions on how far the expression can
+ travel. */
+ int max_distance;
+};
+
+/* Occurrence of an expression.
+ There is one per basic block. If a pattern appears more than once the
+ last appearance is used [or first for anticipatable expressions]. */
+
+struct occr
+{
+ /* Next occurrence of this expression. */
+ struct occr *next;
+ /* The insn that computes the expression. */
+ rtx insn;
+ /* Nonzero if this [anticipatable] occurrence has been deleted. */
+ char deleted_p;
+ /* Nonzero if this [available] occurrence has been copied to
+ reaching_reg. */
+ /* ??? This is mutually exclusive with deleted_p, so they could share
+ the same byte. */
+ char copied_p;
+};
+
+typedef struct occr *occr_t;
+DEF_VEC_P (occr_t);
+DEF_VEC_ALLOC_P (occr_t, heap);
+
+/* Expression and copy propagation hash tables.
+ Each hash table is an array of buckets.
+ ??? It is known that if it were an array of entries, structure elements
+ `next_same_hash' and `bitmap_index' wouldn't be necessary. However, it is
+ not clear whether in the final analysis a sufficient amount of memory would
+ be saved as the size of the available expression bitmaps would be larger
+ [one could build a mapping table without holes afterwards though].
+ Someday I'll perform the computation and figure it out. */
+
+struct hash_table_d
+{
+ /* The table itself.
+ This is an array of `expr_hash_table_size' elements. */
+ struct expr **table;
+
+ /* Size of the hash table, in elements. */
+ unsigned int size;
+
+ /* Number of hash table elements. */
+ unsigned int n_elems;
+
+ /* Whether the table is expression of copy propagation one. */
+ int set_p;
+};
+
+/* Expression hash table. */
+static struct hash_table_d expr_hash_table;
+
+/* Copy propagation hash table. */
+static struct hash_table_d set_hash_table;
+
+/* This is a list of expressions which are MEMs and will be used by load
+ or store motion.
+ Load motion tracks MEMs which aren't killed by
+ anything except itself. (i.e., loads and stores to a single location).
+ We can then allow movement of these MEM refs with a little special
+ allowance. (all stores copy the same value to the reaching reg used
+ for the loads). This means all values used to store into memory must have
+ no side effects so we can re-issue the setter value.
+ Store Motion uses this structure as an expression table to track stores
+ which look interesting, and might be moveable towards the exit block. */
+
+struct ls_expr
+{
+ struct expr * expr; /* Gcse expression reference for LM. */
+ rtx pattern; /* Pattern of this mem. */
+ rtx pattern_regs; /* List of registers mentioned by the mem. */
+ rtx loads; /* INSN list of loads seen. */
+ rtx stores; /* INSN list of stores seen. */
+ struct ls_expr * next; /* Next in the list. */
+ int invalid; /* Invalid for some reason. */
+ int index; /* If it maps to a bitmap index. */
+ unsigned int hash_index; /* Index when in a hash table. */
+ rtx reaching_reg; /* Register to use when re-writing. */
+};
+
+/* Array of implicit set patterns indexed by basic block index. */
+static rtx *implicit_sets;
+
+/* Head of the list of load/store memory refs. */
+static struct ls_expr * pre_ldst_mems = NULL;
+
+/* Hashtable for the load/store memory refs. */
+static htab_t pre_ldst_table = NULL;
+
+/* Bitmap containing one bit for each register in the program.
+ Used when performing GCSE to track which registers have been set since
+ the start of the basic block. */
+static regset reg_set_bitmap;
+
+/* Array, indexed by basic block number for a list of insns which modify
+ memory within that block. */
+static rtx * modify_mem_list;
+static bitmap modify_mem_list_set;
+
+/* This array parallels modify_mem_list, but is kept canonicalized. */
+static rtx * canon_modify_mem_list;
+
+/* Bitmap indexed by block numbers to record which blocks contain
+ function calls. */
+static bitmap blocks_with_calls;
+
+/* Various variables for statistics gathering. */
+
+/* Memory used in a pass.
+ This isn't intended to be absolutely precise. Its intent is only
+ to keep an eye on memory usage. */
+static int bytes_used;
+
+/* GCSE substitutions made. */
+static int gcse_subst_count;
+/* Number of copy instructions created. */
+static int gcse_create_count;
+/* Number of local constants propagated. */
+static int local_const_prop_count;
+/* Number of local copies propagated. */
+static int local_copy_prop_count;
+/* Number of global constants propagated. */
+static int global_const_prop_count;
+/* Number of global copies propagated. */
+static int global_copy_prop_count;
+
+/* Doing code hoisting. */
+static bool doing_code_hoisting_p = false;
+
+/* For available exprs */
+static sbitmap *ae_kill;
+
+static void compute_can_copy (void);
+static void *gmalloc (size_t) ATTRIBUTE_MALLOC;
+static void *gcalloc (size_t, size_t) ATTRIBUTE_MALLOC;
+static void *gcse_alloc (unsigned long);
+static void alloc_gcse_mem (void);
+static void free_gcse_mem (void);
+static void hash_scan_insn (rtx, struct hash_table_d *);
+static void hash_scan_set (rtx, rtx, struct hash_table_d *);
+static void hash_scan_clobber (rtx, rtx, struct hash_table_d *);
+static void hash_scan_call (rtx, rtx, struct hash_table_d *);
+static int want_to_gcse_p (rtx, int *);
+static bool gcse_constant_p (const_rtx);
+static int oprs_unchanged_p (const_rtx, const_rtx, int);
+static int oprs_anticipatable_p (const_rtx, const_rtx);
+static int oprs_available_p (const_rtx, const_rtx);
+static void insert_expr_in_table (rtx, enum machine_mode, rtx, int, int, int,
+ struct hash_table_d *);
+static void insert_set_in_table (rtx, rtx, struct hash_table_d *);
+static unsigned int hash_expr (const_rtx, enum machine_mode, int *, int);
+static unsigned int hash_set (int, int);
+static int expr_equiv_p (const_rtx, const_rtx);
+static void record_last_reg_set_info (rtx, int);
+static void record_last_mem_set_info (rtx);
+static void record_last_set_info (rtx, const_rtx, void *);
+static void compute_hash_table (struct hash_table_d *);
+static void alloc_hash_table (struct hash_table_d *, int);
+static void free_hash_table (struct hash_table_d *);
+static void compute_hash_table_work (struct hash_table_d *);
+static void dump_hash_table (FILE *, const char *, struct hash_table_d *);
+static struct expr *lookup_set (unsigned int, struct hash_table_d *);
+static struct expr *next_set (unsigned int, struct expr *);
+static void reset_opr_set_tables (void);
+static int oprs_not_set_p (const_rtx, const_rtx);
+static void mark_call (rtx);
+static void mark_set (rtx, rtx);
+static void mark_clobber (rtx, rtx);
+static void mark_oprs_set (rtx);
+static void alloc_cprop_mem (int, int);
+static void free_cprop_mem (void);
+static void compute_transp (const_rtx, int, sbitmap *, int);
+static void compute_local_properties (sbitmap *, sbitmap *, sbitmap *,
+ struct hash_table_d *);
+static void compute_cprop_data (void);
+static void find_used_regs (rtx *, void *);
+static int try_replace_reg (rtx, rtx, rtx);
+static struct expr *find_avail_set (int, rtx);
+static int cprop_jump (basic_block, rtx, rtx, rtx, rtx);
+static void mems_conflict_for_gcse_p (rtx, const_rtx, void *);
+static int load_killed_in_block_p (const_basic_block, int, const_rtx, int);
+static void canon_list_insert (rtx, const_rtx, void *);
+static int cprop_insn (rtx);
+static void find_implicit_sets (void);
+static int one_cprop_pass (void);
+static bool constprop_register (rtx, rtx, rtx);
+static struct expr *find_bypass_set (int, int);
+static bool reg_killed_on_edge (const_rtx, const_edge);
+static int bypass_block (basic_block, rtx, rtx);
+static int bypass_conditional_jumps (void);
+static void alloc_pre_mem (int, int);
+static void free_pre_mem (void);
+static void compute_pre_data (void);
+static int pre_expr_reaches_here_p (basic_block, struct expr *,
+ basic_block);
+static void insert_insn_end_basic_block (struct expr *, basic_block);
+static void pre_insert_copy_insn (struct expr *, rtx);
+static void pre_insert_copies (void);
+static int pre_delete (void);
+static int pre_gcse (void);
+static int one_pre_gcse_pass (void);
+static void add_label_notes (rtx, rtx);
+static void alloc_code_hoist_mem (int, int);
+static void free_code_hoist_mem (void);
+static void compute_code_hoist_vbeinout (void);
+static void compute_code_hoist_data (void);
+static int hoist_expr_reaches_here_p (basic_block, int, basic_block, char *,
+ int, int *);
+static int hoist_code (void);
+static int one_code_hoisting_pass (void);
+static rtx process_insert_insn (struct expr *);
+static int pre_edge_insert (struct edge_list *, struct expr **);
+static int pre_expr_reaches_here_p_work (basic_block, struct expr *,
+ basic_block, char *);
+static struct ls_expr * ldst_entry (rtx);
+static void free_ldst_entry (struct ls_expr *);
+static void free_ldst_mems (void);
+static void print_ldst_list (FILE *);
+static struct ls_expr * find_rtx_in_ldst (rtx);
+static inline struct ls_expr * first_ls_expr (void);
+static inline struct ls_expr * next_ls_expr (struct ls_expr *);
+static int simple_mem (const_rtx);
+static void invalidate_any_buried_refs (rtx);
+static void compute_ld_motion_mems (void);
+static void trim_ld_motion_mems (void);
+static void update_ld_motion_stores (struct expr *);
+static void free_insn_expr_list_list (rtx *);
+static void clear_modify_mem_tables (void);
+static void free_modify_mem_tables (void);
+static rtx gcse_emit_move_after (rtx, rtx, rtx);
+static void local_cprop_find_used_regs (rtx *, void *);
+static bool do_local_cprop (rtx, rtx);
+static int local_cprop_pass (void);
+static bool is_too_expensive (const char *);
+
+#define GNEW(T) ((T *) gmalloc (sizeof (T)))
+#define GCNEW(T) ((T *) gcalloc (1, sizeof (T)))
+
+#define GNEWVEC(T, N) ((T *) gmalloc (sizeof (T) * (N)))
+#define GCNEWVEC(T, N) ((T *) gcalloc ((N), sizeof (T)))
+
+#define GNEWVAR(T, S) ((T *) gmalloc ((S)))
+#define GCNEWVAR(T, S) ((T *) gcalloc (1, (S)))
+
+#define GOBNEW(T) ((T *) gcse_alloc (sizeof (T)))
+#define GOBNEWVAR(T, S) ((T *) gcse_alloc ((S)))
+
+/* Misc. utilities. */
+
+#define can_copy \
+ (this_target_gcse->x_can_copy)
+#define can_copy_init_p \
+ (this_target_gcse->x_can_copy_init_p)
+
+/* Compute which modes support reg/reg copy operations. */
+
+static void
+compute_can_copy (void)
+{
+ int i;
+#ifndef AVOID_CCMODE_COPIES
+ rtx reg, insn;
+#endif
+ memset (can_copy, 0, NUM_MACHINE_MODES);
+
+ start_sequence ();
+ for (i = 0; i < NUM_MACHINE_MODES; i++)
+ if (GET_MODE_CLASS (i) == MODE_CC)
+ {
+#ifdef AVOID_CCMODE_COPIES
+ can_copy[i] = 0;
+#else
+ reg = gen_rtx_REG ((enum machine_mode) i, LAST_VIRTUAL_REGISTER + 1);
+ insn = emit_insn (gen_rtx_SET (VOIDmode, reg, reg));
+ if (recog (PATTERN (insn), insn, NULL) >= 0)
+ can_copy[i] = 1;
+#endif
+ }
+ else
+ can_copy[i] = 1;
+
+ end_sequence ();
+}
+
+/* Returns whether the mode supports reg/reg copy operations. */
+
+bool
+can_copy_p (enum machine_mode mode)
+{
+ if (! can_copy_init_p)
+ {
+ compute_can_copy ();
+ can_copy_init_p = true;
+ }
+
+ return can_copy[mode] != 0;
+}
+
+
+/* Cover function to xmalloc to record bytes allocated. */
+
+static void *
+gmalloc (size_t size)
+{
+ bytes_used += size;
+ return xmalloc (size);
+}
+
+/* Cover function to xcalloc to record bytes allocated. */
+
+static void *
+gcalloc (size_t nelem, size_t elsize)
+{
+ bytes_used += nelem * elsize;
+ return xcalloc (nelem, elsize);
+}
+
+/* Cover function to obstack_alloc. */
+
+static void *
+gcse_alloc (unsigned long size)
+{
+ bytes_used += size;
+ return obstack_alloc (&gcse_obstack, size);
+}
+
+/* Allocate memory for the reg/memory set tracking tables.
+ This is called at the start of each pass. */
+
+static void
+alloc_gcse_mem (void)
+{
+ /* Allocate vars to track sets of regs. */
+ reg_set_bitmap = ALLOC_REG_SET (NULL);
+
+ /* Allocate array to keep a list of insns which modify memory in each
+ basic block. */
+ modify_mem_list = GCNEWVEC (rtx, last_basic_block);
+ canon_modify_mem_list = GCNEWVEC (rtx, last_basic_block);
+ modify_mem_list_set = BITMAP_ALLOC (NULL);
+ blocks_with_calls = BITMAP_ALLOC (NULL);
+}
+
+/* Free memory allocated by alloc_gcse_mem. */
+
+static void
+free_gcse_mem (void)
+{
+ free_modify_mem_tables ();
+ BITMAP_FREE (modify_mem_list_set);
+ BITMAP_FREE (blocks_with_calls);
+}
+
+/* Compute the local properties of each recorded expression.
+
+ Local properties are those that are defined by the block, irrespective of
+ other blocks.
+
+ An expression is transparent in a block if its operands are not modified
+ in the block.
+
+ An expression is computed (locally available) in a block if it is computed
+ at least once and expression would contain the same value if the
+ computation was moved to the end of the block.
+
+ An expression is locally anticipatable in a block if it is computed at
+ least once and expression would contain the same value if the computation
+ was moved to the beginning of the block.
+
+ We call this routine for cprop, pre and code hoisting. They all compute
+ basically the same information and thus can easily share this code.
+
+ TRANSP, COMP, and ANTLOC are destination sbitmaps for recording local
+ properties. If NULL, then it is not necessary to compute or record that
+ particular property.
+
+ TABLE controls which hash table to look at. If it is set hash table,
+ additionally, TRANSP is computed as ~TRANSP, since this is really cprop's
+ ABSALTERED. */
+
+static void
+compute_local_properties (sbitmap *transp, sbitmap *comp, sbitmap *antloc,
+ struct hash_table_d *table)
+{
+ unsigned int i;
+
+ /* Initialize any bitmaps that were passed in. */
+ if (transp)
+ {
+ if (table->set_p)
+ sbitmap_vector_zero (transp, last_basic_block);
+ else
+ sbitmap_vector_ones (transp, last_basic_block);
+ }
+
+ if (comp)
+ sbitmap_vector_zero (comp, last_basic_block);
+ if (antloc)
+ sbitmap_vector_zero (antloc, last_basic_block);
+
+ for (i = 0; i < table->size; i++)
+ {
+ struct expr *expr;
+
+ for (expr = table->table[i]; expr != NULL; expr = expr->next_same_hash)
+ {
+ int indx = expr->bitmap_index;
+ struct occr *occr;
+
+ /* The expression is transparent in this block if it is not killed.
+ We start by assuming all are transparent [none are killed], and
+ then reset the bits for those that are. */
+ if (transp)
+ compute_transp (expr->expr, indx, transp, table->set_p);
+
+ /* The occurrences recorded in antic_occr are exactly those that
+ we want to set to nonzero in ANTLOC. */
+ if (antloc)
+ for (occr = expr->antic_occr; occr != NULL; occr = occr->next)
+ {
+ SET_BIT (antloc[BLOCK_FOR_INSN (occr->insn)->index], indx);
+
+ /* While we're scanning the table, this is a good place to
+ initialize this. */
+ occr->deleted_p = 0;
+ }
+
+ /* The occurrences recorded in avail_occr are exactly those that
+ we want to set to nonzero in COMP. */
+ if (comp)
+ for (occr = expr->avail_occr; occr != NULL; occr = occr->next)
+ {
+ SET_BIT (comp[BLOCK_FOR_INSN (occr->insn)->index], indx);
+
+ /* While we're scanning the table, this is a good place to
+ initialize this. */
+ occr->copied_p = 0;
+ }
+
+ /* While we're scanning the table, this is a good place to
+ initialize this. */
+ expr->reaching_reg = 0;
+ }
+ }
+}
+
+/* Hash table support. */
+
+struct reg_avail_info
+{
+ basic_block last_bb;
+ int first_set;
+ int last_set;
+};
+
+static struct reg_avail_info *reg_avail_info;
+static basic_block current_bb;
+
+
+/* See whether X, the source of a set, is something we want to consider for
+ GCSE. */
+
+static int
+want_to_gcse_p (rtx x, int *max_distance_ptr)
+{
+#ifdef STACK_REGS
+ /* On register stack architectures, don't GCSE constants from the
+ constant pool, as the benefits are often swamped by the overhead
+ of shuffling the register stack between basic blocks. */
+ if (IS_STACK_MODE (GET_MODE (x)))
+ x = avoid_constant_pool_reference (x);
+#endif
+
+ /* GCSE'ing constants:
+
+ We do not specifically distinguish between constant and non-constant
+ expressions in PRE and Hoist. We use rtx_cost below to limit
+ the maximum distance simple expressions can travel.
+
+ Nevertheless, constants are much easier to GCSE, and, hence,
+ it is easy to overdo the optimizations. Usually, excessive PRE and
+ Hoisting of constant leads to increased register pressure.
+
+ RA can deal with this by rematerialing some of the constants.
+ Therefore, it is important that the back-end generates sets of constants
+ in a way that allows reload rematerialize them under high register
+ pressure, i.e., a pseudo register with REG_EQUAL to constant
+ is set only once. Failing to do so will result in IRA/reload
+ spilling such constants under high register pressure instead of
+ rematerializing them. */
+
+ switch (GET_CODE (x))
+ {
+ case REG:
+ case SUBREG:
+ case CALL:
+ return 0;
+
+ case CONST_INT:
+ case CONST_DOUBLE:
+ case CONST_FIXED:
+ case CONST_VECTOR:
+ if (!doing_code_hoisting_p)
+ /* Do not PRE constants. */
+ return 0;
+
+ /* FALLTHRU */
+
+ default:
+ if (doing_code_hoisting_p)
+ /* PRE doesn't implement max_distance restriction. */
+ {
+ int cost;
+ int max_distance;
+
+ gcc_assert (!optimize_function_for_speed_p (cfun)
+ && optimize_function_for_size_p (cfun));
+ cost = rtx_cost (x, SET, 0);
+
+ if (cost < COSTS_N_INSNS (GCSE_UNRESTRICTED_COST))
+ {
+ max_distance = (GCSE_COST_DISTANCE_RATIO * cost) / 10;
+ if (max_distance == 0)
+ return 0;
+
+ gcc_assert (max_distance > 0);
+ }
+ else
+ max_distance = 0;
+
+ if (max_distance_ptr)
+ *max_distance_ptr = max_distance;
+ }
+
+ return can_assign_to_reg_without_clobbers_p (x);
+ }
+}
+
+/* Used internally by can_assign_to_reg_without_clobbers_p. */
+
+static GTY(()) rtx test_insn;
+
+/* Return true if we can assign X to a pseudo register such that the
+ resulting insn does not result in clobbering a hard register as a
+ side-effect.
+
+ Additionally, if the target requires it, check that the resulting insn
+ can be copied. If it cannot, this means that X is special and probably
+ has hidden side-effects we don't want to mess with.
+
+ This function is typically used by code motion passes, to verify
+ that it is safe to insert an insn without worrying about clobbering
+ maybe live hard regs. */
+
+bool
+can_assign_to_reg_without_clobbers_p (rtx x)
+{
+ int num_clobbers = 0;
+ int icode;
+
+ /* If this is a valid operand, we are OK. If it's VOIDmode, we aren't. */
+ if (general_operand (x, GET_MODE (x)))
+ return 1;
+ else if (GET_MODE (x) == VOIDmode)
+ return 0;
+
+ /* Otherwise, check if we can make a valid insn from it. First initialize
+ our test insn if we haven't already. */
+ if (test_insn == 0)
+ {
+ test_insn
+ = make_insn_raw (gen_rtx_SET (VOIDmode,
+ gen_rtx_REG (word_mode,
+ FIRST_PSEUDO_REGISTER * 2),
+ const0_rtx));
+ NEXT_INSN (test_insn) = PREV_INSN (test_insn) = 0;
+ }
+
+ /* Now make an insn like the one we would make when GCSE'ing and see if
+ valid. */
+ PUT_MODE (SET_DEST (PATTERN (test_insn)), GET_MODE (x));
+ SET_SRC (PATTERN (test_insn)) = x;
+
+ icode = recog (PATTERN (test_insn), test_insn, &num_clobbers);
+ if (icode < 0)
+ return false;
+
+ if (num_clobbers > 0 && added_clobbers_hard_reg_p (icode))
+ return false;
+
+ if (targetm.cannot_copy_insn_p && targetm.cannot_copy_insn_p (test_insn))
+ return false;
+
+ return true;
+}
+
+/* Return nonzero if the operands of expression X are unchanged from the
+ start of INSN's basic block up to but not including INSN (if AVAIL_P == 0),
+ or from INSN to the end of INSN's basic block (if AVAIL_P != 0). */
+
+static int
+oprs_unchanged_p (const_rtx x, const_rtx insn, int avail_p)
+{
+ int i, j;
+ enum rtx_code code;
+ const char *fmt;
+
+ if (x == 0)
+ return 1;
+
+ code = GET_CODE (x);
+ switch (code)
+ {
+ case REG:
+ {
+ struct reg_avail_info *info = &reg_avail_info[REGNO (x)];
+
+ if (info->last_bb != current_bb)
+ return 1;
+ if (avail_p)
+ return info->last_set < DF_INSN_LUID (insn);
+ else
+ return info->first_set >= DF_INSN_LUID (insn);
+ }
+
+ case MEM:
+ if (load_killed_in_block_p (current_bb, DF_INSN_LUID (insn),
+ x, avail_p))
+ return 0;
+ else
+ return oprs_unchanged_p (XEXP (x, 0), insn, avail_p);
+
+ case PRE_DEC:
+ case PRE_INC:
+ case POST_DEC:
+ case POST_INC:
+ case PRE_MODIFY:
+ case POST_MODIFY:
+ return 0;
+
+ case PC:
+ case CC0: /*FIXME*/
+ case CONST:
+ case CONST_INT:
+ case CONST_DOUBLE:
+ case CONST_FIXED:
+ case CONST_VECTOR:
+ case SYMBOL_REF:
+ case LABEL_REF:
+ case ADDR_VEC:
+ case ADDR_DIFF_VEC:
+ return 1;
+
+ default:
+ break;
+ }
+
+ for (i = GET_RTX_LENGTH (code) - 1, fmt = GET_RTX_FORMAT (code); i >= 0; i--)
+ {
+ if (fmt[i] == 'e')
+ {
+ /* If we are about to do the last recursive call needed at this
+ level, change it into iteration. This function is called enough
+ to be worth it. */
+ if (i == 0)
+ return oprs_unchanged_p (XEXP (x, i), insn, avail_p);
+
+ else if (! oprs_unchanged_p (XEXP (x, i), insn, avail_p))
+ return 0;
+ }
+ else if (fmt[i] == 'E')
+ for (j = 0; j < XVECLEN (x, i); j++)
+ if (! oprs_unchanged_p (XVECEXP (x, i, j), insn, avail_p))
+ return 0;
+ }
+
+ return 1;
+}
+
+/* Used for communication between mems_conflict_for_gcse_p and
+ load_killed_in_block_p. Nonzero if mems_conflict_for_gcse_p finds a
+ conflict between two memory references. */
+static int gcse_mems_conflict_p;
+
+/* Used for communication between mems_conflict_for_gcse_p and
+ load_killed_in_block_p. A memory reference for a load instruction,
+ mems_conflict_for_gcse_p will see if a memory store conflicts with
+ this memory load. */
+static const_rtx gcse_mem_operand;
+
+/* DEST is the output of an instruction. If it is a memory reference, and
+ possibly conflicts with the load found in gcse_mem_operand, then set
+ gcse_mems_conflict_p to a nonzero value. */
+
+static void
+mems_conflict_for_gcse_p (rtx dest, const_rtx setter ATTRIBUTE_UNUSED,
+ void *data ATTRIBUTE_UNUSED)
+{
+ while (GET_CODE (dest) == SUBREG
+ || GET_CODE (dest) == ZERO_EXTRACT
+ || GET_CODE (dest) == STRICT_LOW_PART)
+ dest = XEXP (dest, 0);
+
+ /* If DEST is not a MEM, then it will not conflict with the load. Note
+ that function calls are assumed to clobber memory, but are handled
+ elsewhere. */
+ if (! MEM_P (dest))
+ return;
+
+ /* If we are setting a MEM in our list of specially recognized MEMs,
+ don't mark as killed this time. */
+
+ if (expr_equiv_p (dest, gcse_mem_operand) && pre_ldst_mems != NULL)
+ {
+ if (!find_rtx_in_ldst (dest))
+ gcse_mems_conflict_p = 1;
+ return;
+ }
+
+ if (true_dependence (dest, GET_MODE (dest), gcse_mem_operand,
+ rtx_addr_varies_p))
+ gcse_mems_conflict_p = 1;
+}
+
+/* Return nonzero if the expression in X (a memory reference) is killed
+ in block BB before or after the insn with the LUID in UID_LIMIT.
+ AVAIL_P is nonzero for kills after UID_LIMIT, and zero for kills
+ before UID_LIMIT.
+
+ To check the entire block, set UID_LIMIT to max_uid + 1 and
+ AVAIL_P to 0. */
+
+static int
+load_killed_in_block_p (const_basic_block bb, int uid_limit, const_rtx x, int avail_p)
+{
+ rtx list_entry = modify_mem_list[bb->index];
+
+ /* If this is a readonly then we aren't going to be changing it. */
+ if (MEM_READONLY_P (x))
+ return 0;
+
+ while (list_entry)
+ {
+ rtx setter;
+ /* Ignore entries in the list that do not apply. */
+ if ((avail_p
+ && DF_INSN_LUID (XEXP (list_entry, 0)) < uid_limit)
+ || (! avail_p
+ && DF_INSN_LUID (XEXP (list_entry, 0)) > uid_limit))
+ {
+ list_entry = XEXP (list_entry, 1);
+ continue;
+ }
+
+ setter = XEXP (list_entry, 0);
+
+ /* If SETTER is a call everything is clobbered. Note that calls
+ to pure functions are never put on the list, so we need not
+ worry about them. */
+ if (CALL_P (setter))
+ return 1;
+
+ /* SETTER must be an INSN of some kind that sets memory. Call
+ note_stores to examine each hunk of memory that is modified.
+
+ The note_stores interface is pretty limited, so we have to
+ communicate via global variables. Yuk. */
+ gcse_mem_operand = x;
+ gcse_mems_conflict_p = 0;
+ note_stores (PATTERN (setter), mems_conflict_for_gcse_p, NULL);
+ if (gcse_mems_conflict_p)
+ return 1;
+ list_entry = XEXP (list_entry, 1);
+ }
+ return 0;
+}
+
+/* Return nonzero if the operands of expression X are unchanged from
+ the start of INSN's basic block up to but not including INSN. */
+
+static int
+oprs_anticipatable_p (const_rtx x, const_rtx insn)
+{
+ return oprs_unchanged_p (x, insn, 0);
+}
+
+/* Return nonzero if the operands of expression X are unchanged from
+ INSN to the end of INSN's basic block. */
+
+static int
+oprs_available_p (const_rtx x, const_rtx insn)
+{
+ return oprs_unchanged_p (x, insn, 1);
+}
+
+/* Hash expression X.
+
+ MODE is only used if X is a CONST_INT. DO_NOT_RECORD_P is a boolean
+ indicating if a volatile operand is found or if the expression contains
+ something we don't want to insert in the table. HASH_TABLE_SIZE is
+ the current size of the hash table to be probed. */
+
+static unsigned int
+hash_expr (const_rtx x, enum machine_mode mode, int *do_not_record_p,
+ int hash_table_size)
+{
+ unsigned int hash;
+
+ *do_not_record_p = 0;
+
+ hash = hash_rtx (x, mode, do_not_record_p,
+ NULL, /*have_reg_qty=*/false);
+ return hash % hash_table_size;
+}
+
+/* Hash a set of register REGNO.
+
+ Sets are hashed on the register that is set. This simplifies the PRE copy
+ propagation code.
+
+ ??? May need to make things more elaborate. Later, as necessary. */
+
+static unsigned int
+hash_set (int regno, int hash_table_size)
+{
+ unsigned int hash;
+
+ hash = regno;
+ return hash % hash_table_size;
+}
+
+/* Return nonzero if exp1 is equivalent to exp2. */
+
+static int
+expr_equiv_p (const_rtx x, const_rtx y)
+{
+ return exp_equiv_p (x, y, 0, true);
+}
+
+/* Insert expression X in INSN in the hash TABLE.
+ If it is already present, record it as the last occurrence in INSN's
+ basic block.
+
+ MODE is the mode of the value X is being stored into.
+ It is only used if X is a CONST_INT.
+
+ ANTIC_P is nonzero if X is an anticipatable expression.
+ AVAIL_P is nonzero if X is an available expression.
+
+ MAX_DISTANCE is the maximum distance in instructions this expression can
+ be moved. */
+
+static void
+insert_expr_in_table (rtx x, enum machine_mode mode, rtx insn, int antic_p,
+ int avail_p, int max_distance, struct hash_table_d *table)
+{
+ int found, do_not_record_p;
+ unsigned int hash;
+ struct expr *cur_expr, *last_expr = NULL;
+ struct occr *antic_occr, *avail_occr;
+
+ hash = hash_expr (x, mode, &do_not_record_p, table->size);
+
+ /* Do not insert expression in table if it contains volatile operands,
+ or if hash_expr determines the expression is something we don't want
+ to or can't handle. */
+ if (do_not_record_p)
+ return;
+
+ cur_expr = table->table[hash];
+ found = 0;
+
+ while (cur_expr && 0 == (found = expr_equiv_p (cur_expr->expr, x)))
+ {
+ /* If the expression isn't found, save a pointer to the end of
+ the list. */
+ last_expr = cur_expr;
+ cur_expr = cur_expr->next_same_hash;
+ }
+
+ if (! found)
+ {
+ cur_expr = GOBNEW (struct expr);
+ bytes_used += sizeof (struct expr);
+ if (table->table[hash] == NULL)
+ /* This is the first pattern that hashed to this index. */
+ table->table[hash] = cur_expr;
+ else
+ /* Add EXPR to end of this hash chain. */
+ last_expr->next_same_hash = cur_expr;
+
+ /* Set the fields of the expr element. */
+ cur_expr->expr = x;
+ cur_expr->bitmap_index = table->n_elems++;
+ cur_expr->next_same_hash = NULL;
+ cur_expr->antic_occr = NULL;
+ cur_expr->avail_occr = NULL;
+ gcc_assert (max_distance >= 0);
+ cur_expr->max_distance = max_distance;
+ }
+ else
+ gcc_assert (cur_expr->max_distance == max_distance);
+
+ /* Now record the occurrence(s). */
+ if (antic_p)
+ {
+ antic_occr = cur_expr->antic_occr;
+
+ if (antic_occr
+ && BLOCK_FOR_INSN (antic_occr->insn) != BLOCK_FOR_INSN (insn))
+ antic_occr = NULL;
+
+ if (antic_occr)
+ /* Found another instance of the expression in the same basic block.
+ Prefer the currently recorded one. We want the first one in the
+ block and the block is scanned from start to end. */
+ ; /* nothing to do */
+ else
+ {
+ /* First occurrence of this expression in this basic block. */
+ antic_occr = GOBNEW (struct occr);
+ bytes_used += sizeof (struct occr);
+ antic_occr->insn = insn;
+ antic_occr->next = cur_expr->antic_occr;
+ antic_occr->deleted_p = 0;
+ cur_expr->antic_occr = antic_occr;
+ }
+ }
+
+ if (avail_p)
+ {
+ avail_occr = cur_expr->avail_occr;
+
+ if (avail_occr
+ && BLOCK_FOR_INSN (avail_occr->insn) == BLOCK_FOR_INSN (insn))
+ {
+ /* Found another instance of the expression in the same basic block.
+ Prefer this occurrence to the currently recorded one. We want
+ the last one in the block and the block is scanned from start
+ to end. */
+ avail_occr->insn = insn;
+ }
+ else
+ {
+ /* First occurrence of this expression in this basic block. */
+ avail_occr = GOBNEW (struct occr);
+ bytes_used += sizeof (struct occr);
+ avail_occr->insn = insn;
+ avail_occr->next = cur_expr->avail_occr;
+ avail_occr->deleted_p = 0;
+ cur_expr->avail_occr = avail_occr;
+ }
+ }
+}
+
+/* Insert pattern X in INSN in the hash table.
+ X is a SET of a reg to either another reg or a constant.
+ If it is already present, record it as the last occurrence in INSN's
+ basic block. */
+
+static void
+insert_set_in_table (rtx x, rtx insn, struct hash_table_d *table)
+{
+ int found;
+ unsigned int hash;
+ struct expr *cur_expr, *last_expr = NULL;
+ struct occr *cur_occr;
+
+ gcc_assert (GET_CODE (x) == SET && REG_P (SET_DEST (x)));
+
+ hash = hash_set (REGNO (SET_DEST (x)), table->size);
+
+ cur_expr = table->table[hash];
+ found = 0;
+
+ while (cur_expr && 0 == (found = expr_equiv_p (cur_expr->expr, x)))
+ {
+ /* If the expression isn't found, save a pointer to the end of
+ the list. */
+ last_expr = cur_expr;
+ cur_expr = cur_expr->next_same_hash;
+ }
+
+ if (! found)
+ {
+ cur_expr = GOBNEW (struct expr);
+ bytes_used += sizeof (struct expr);
+ if (table->table[hash] == NULL)
+ /* This is the first pattern that hashed to this index. */
+ table->table[hash] = cur_expr;
+ else
+ /* Add EXPR to end of this hash chain. */
+ last_expr->next_same_hash = cur_expr;
+
+ /* Set the fields of the expr element.
+ We must copy X because it can be modified when copy propagation is
+ performed on its operands. */
+ cur_expr->expr = copy_rtx (x);
+ cur_expr->bitmap_index = table->n_elems++;
+ cur_expr->next_same_hash = NULL;
+ cur_expr->antic_occr = NULL;
+ cur_expr->avail_occr = NULL;
+ /* Not used for set_p tables. */
+ cur_expr->max_distance = 0;
+ }
+
+ /* Now record the occurrence. */
+ cur_occr = cur_expr->avail_occr;
+
+ if (cur_occr
+ && BLOCK_FOR_INSN (cur_occr->insn) == BLOCK_FOR_INSN (insn))
+ {
+ /* Found another instance of the expression in the same basic block.
+ Prefer this occurrence to the currently recorded one. We want
+ the last one in the block and the block is scanned from start
+ to end. */
+ cur_occr->insn = insn;
+ }
+ else
+ {
+ /* First occurrence of this expression in this basic block. */
+ cur_occr = GOBNEW (struct occr);
+ bytes_used += sizeof (struct occr);
+ cur_occr->insn = insn;
+ cur_occr->next = cur_expr->avail_occr;
+ cur_occr->deleted_p = 0;
+ cur_expr->avail_occr = cur_occr;
+ }
+}
+
+/* Determine whether the rtx X should be treated as a constant for
+ the purposes of GCSE's constant propagation. */
+
+static bool
+gcse_constant_p (const_rtx x)
+{
+ /* Consider a COMPARE of two integers constant. */
+ if (GET_CODE (x) == COMPARE
+ && CONST_INT_P (XEXP (x, 0))
+ && CONST_INT_P (XEXP (x, 1)))
+ return true;
+
+ /* Consider a COMPARE of the same registers is a constant
+ if they are not floating point registers. */
+ if (GET_CODE(x) == COMPARE
+ && REG_P (XEXP (x, 0)) && REG_P (XEXP (x, 1))
+ && REGNO (XEXP (x, 0)) == REGNO (XEXP (x, 1))
+ && ! FLOAT_MODE_P (GET_MODE (XEXP (x, 0)))
+ && ! FLOAT_MODE_P (GET_MODE (XEXP (x, 1))))
+ return true;
+
+ /* Since X might be inserted more than once we have to take care that it
+ is sharable. */
+ return CONSTANT_P (x) && (GET_CODE (x) != CONST || shared_const_p (x));
+}
+
+/* Scan pattern PAT of INSN and add an entry to the hash TABLE (set or
+ expression one). */
+
+static void
+hash_scan_set (rtx pat, rtx insn, struct hash_table_d *table)
+{
+ rtx src = SET_SRC (pat);
+ rtx dest = SET_DEST (pat);
+ rtx note;
+
+ if (GET_CODE (src) == CALL)
+ hash_scan_call (src, insn, table);
+
+ else if (REG_P (dest))
+ {
+ unsigned int regno = REGNO (dest);
+ rtx tmp;
+ int max_distance = 0;
+
+ /* See if a REG_EQUAL note shows this equivalent to a simpler expression.
+
+ This allows us to do a single GCSE pass and still eliminate
+ redundant constants, addresses or other expressions that are
+ constructed with multiple instructions.
+
+ However, keep the original SRC if INSN is a simple reg-reg move. In
+ In this case, there will almost always be a REG_EQUAL note on the
+ insn that sets SRC. By recording the REG_EQUAL value here as SRC
+ for INSN, we miss copy propagation opportunities and we perform the
+ same PRE GCSE operation repeatedly on the same REG_EQUAL value if we
+ do more than one PRE GCSE pass.
+
+ Note that this does not impede profitable constant propagations. We
+ "look through" reg-reg sets in lookup_avail_set. */
+ note = find_reg_equal_equiv_note (insn);
+ if (note != 0
+ && REG_NOTE_KIND (note) == REG_EQUAL
+ && !REG_P (src)
+ && (table->set_p
+ ? gcse_constant_p (XEXP (note, 0))
+ : want_to_gcse_p (XEXP (note, 0), NULL)))
+ src = XEXP (note, 0), pat = gen_rtx_SET (VOIDmode, dest, src);
+
+ /* Only record sets of pseudo-regs in the hash table. */
+ if (! table->set_p
+ && regno >= FIRST_PSEUDO_REGISTER
+ /* Don't GCSE something if we can't do a reg/reg copy. */
+ && can_copy_p (GET_MODE (dest))
+ /* GCSE commonly inserts instruction after the insn. We can't
+ do that easily for EH edges so disable GCSE on these for now. */
+ /* ??? We can now easily create new EH landing pads at the
+ gimple level, for splitting edges; there's no reason we
+ can't do the same thing at the rtl level. */
+ && !can_throw_internal (insn)
+ /* Is SET_SRC something we want to gcse? */
+ && want_to_gcse_p (src, &max_distance)
+ /* Don't CSE a nop. */
+ && ! set_noop_p (pat)
+ /* Don't GCSE if it has attached REG_EQUIV note.
+ At this point this only function parameters should have
+ REG_EQUIV notes and if the argument slot is used somewhere
+ explicitly, it means address of parameter has been taken,
+ so we should not extend the lifetime of the pseudo. */
+ && (note == NULL_RTX || ! MEM_P (XEXP (note, 0))))
+ {
+ /* An expression is not anticipatable if its operands are
+ modified before this insn or if this is not the only SET in
+ this insn. The latter condition does not have to mean that
+ SRC itself is not anticipatable, but we just will not be
+ able to handle code motion of insns with multiple sets. */
+ int antic_p = oprs_anticipatable_p (src, insn)
+ && !multiple_sets (insn);
+ /* An expression is not available if its operands are
+ subsequently modified, including this insn. It's also not
+ available if this is a branch, because we can't insert
+ a set after the branch. */
+ int avail_p = (oprs_available_p (src, insn)
+ && ! JUMP_P (insn));
+
+ insert_expr_in_table (src, GET_MODE (dest), insn, antic_p, avail_p,
+ max_distance, table);
+ }
+
+ /* Record sets for constant/copy propagation. */
+ else if (table->set_p
+ && regno >= FIRST_PSEUDO_REGISTER
+ && ((REG_P (src)
+ && REGNO (src) >= FIRST_PSEUDO_REGISTER
+ && can_copy_p (GET_MODE (dest))
+ && REGNO (src) != regno)
+ || gcse_constant_p (src))
+ /* A copy is not available if its src or dest is subsequently
+ modified. Here we want to search from INSN+1 on, but
+ oprs_available_p searches from INSN on. */
+ && (insn == BB_END (BLOCK_FOR_INSN (insn))
+ || (tmp = next_nonnote_nondebug_insn (insn)) == NULL_RTX
+ || BLOCK_FOR_INSN (tmp) != BLOCK_FOR_INSN (insn)
+ || oprs_available_p (pat, tmp)))
+ insert_set_in_table (pat, insn, table);
+ }
+ /* In case of store we want to consider the memory value as available in
+ the REG stored in that memory. This makes it possible to remove
+ redundant loads from due to stores to the same location. */
+ else if (flag_gcse_las && REG_P (src) && MEM_P (dest))
+ {
+ unsigned int regno = REGNO (src);
+ int max_distance = 0;
+
+ /* Do not do this for constant/copy propagation. */
+ if (! table->set_p
+ /* Only record sets of pseudo-regs in the hash table. */
+ && regno >= FIRST_PSEUDO_REGISTER
+ /* Don't GCSE something if we can't do a reg/reg copy. */
+ && can_copy_p (GET_MODE (src))
+ /* GCSE commonly inserts instruction after the insn. We can't
+ do that easily for EH edges so disable GCSE on these for now. */
+ && !can_throw_internal (insn)
+ /* Is SET_DEST something we want to gcse? */
+ && want_to_gcse_p (dest, &max_distance)
+ /* Don't CSE a nop. */
+ && ! set_noop_p (pat)
+ /* Don't GCSE if it has attached REG_EQUIV note.
+ At this point this only function parameters should have
+ REG_EQUIV notes and if the argument slot is used somewhere
+ explicitly, it means address of parameter has been taken,
+ so we should not extend the lifetime of the pseudo. */
+ && ((note = find_reg_note (insn, REG_EQUIV, NULL_RTX)) == 0
+ || ! MEM_P (XEXP (note, 0))))
+ {
+ /* Stores are never anticipatable. */
+ int antic_p = 0;
+ /* An expression is not available if its operands are
+ subsequently modified, including this insn. It's also not
+ available if this is a branch, because we can't insert
+ a set after the branch. */
+ int avail_p = oprs_available_p (dest, insn)
+ && ! JUMP_P (insn);
+
+ /* Record the memory expression (DEST) in the hash table. */
+ insert_expr_in_table (dest, GET_MODE (dest), insn,
+ antic_p, avail_p, max_distance, table);
+ }
+ }
+}
+
+static void
+hash_scan_clobber (rtx x ATTRIBUTE_UNUSED, rtx insn ATTRIBUTE_UNUSED,
+ struct hash_table_d *table ATTRIBUTE_UNUSED)
+{
+ /* Currently nothing to do. */
+}
+
+static void
+hash_scan_call (rtx x ATTRIBUTE_UNUSED, rtx insn ATTRIBUTE_UNUSED,
+ struct hash_table_d *table ATTRIBUTE_UNUSED)
+{
+ /* Currently nothing to do. */
+}
+
+/* Process INSN and add hash table entries as appropriate.
+
+ Only available expressions that set a single pseudo-reg are recorded.
+
+ Single sets in a PARALLEL could be handled, but it's an extra complication
+ that isn't dealt with right now. The trick is handling the CLOBBERs that
+ are also in the PARALLEL. Later.
+
+ If SET_P is nonzero, this is for the assignment hash table,
+ otherwise it is for the expression hash table. */
+
+static void
+hash_scan_insn (rtx insn, struct hash_table_d *table)
+{
+ rtx pat = PATTERN (insn);
+ int i;
+
+ /* Pick out the sets of INSN and for other forms of instructions record
+ what's been modified. */
+
+ if (GET_CODE (pat) == SET)
+ hash_scan_set (pat, insn, table);
+ else if (GET_CODE (pat) == PARALLEL)
+ for (i = 0; i < XVECLEN (pat, 0); i++)
+ {
+ rtx x = XVECEXP (pat, 0, i);
+
+ if (GET_CODE (x) == SET)
+ hash_scan_set (x, insn, table);
+ else if (GET_CODE (x) == CLOBBER)
+ hash_scan_clobber (x, insn, table);
+ else if (GET_CODE (x) == CALL)
+ hash_scan_call (x, insn, table);
+ }
+
+ else if (GET_CODE (pat) == CLOBBER)
+ hash_scan_clobber (pat, insn, table);
+ else if (GET_CODE (pat) == CALL)
+ hash_scan_call (pat, insn, table);
+}
+
+static void
+dump_hash_table (FILE *file, const char *name, struct hash_table_d *table)
+{
+ int i;
+ /* Flattened out table, so it's printed in proper order. */
+ struct expr **flat_table;
+ unsigned int *hash_val;
+ struct expr *expr;
+
+ flat_table = XCNEWVEC (struct expr *, table->n_elems);
+ hash_val = XNEWVEC (unsigned int, table->n_elems);
+
+ for (i = 0; i < (int) table->size; i++)
+ for (expr = table->table[i]; expr != NULL; expr = expr->next_same_hash)
+ {
+ flat_table[expr->bitmap_index] = expr;
+ hash_val[expr->bitmap_index] = i;
+ }
+
+ fprintf (file, "%s hash table (%d buckets, %d entries)\n",
+ name, table->size, table->n_elems);
+
+ for (i = 0; i < (int) table->n_elems; i++)
+ if (flat_table[i] != 0)
+ {
+ expr = flat_table[i];
+ fprintf (file, "Index %d (hash value %d; max distance %d)\n ",
+ expr->bitmap_index, hash_val[i], expr->max_distance);
+ print_rtl (file, expr->expr);
+ fprintf (file, "\n");
+ }
+
+ fprintf (file, "\n");
+
+ free (flat_table);
+ free (hash_val);
+}
+
+/* Record register first/last/block set information for REGNO in INSN.
+
+ first_set records the first place in the block where the register
+ is set and is used to compute "anticipatability".
+
+ last_set records the last place in the block where the register
+ is set and is used to compute "availability".
+
+ last_bb records the block for which first_set and last_set are
+ valid, as a quick test to invalidate them. */
+
+static void
+record_last_reg_set_info (rtx insn, int regno)
+{
+ struct reg_avail_info *info = &reg_avail_info[regno];
+ int luid = DF_INSN_LUID (insn);
+
+ info->last_set = luid;
+ if (info->last_bb != current_bb)
+ {
+ info->last_bb = current_bb;
+ info->first_set = luid;
+ }
+}
+
+
+/* Record all of the canonicalized MEMs of record_last_mem_set_info's insn.
+ Note we store a pair of elements in the list, so they have to be
+ taken off pairwise. */
+
+static void
+canon_list_insert (rtx dest ATTRIBUTE_UNUSED, const_rtx unused1 ATTRIBUTE_UNUSED,
+ void * v_insn)
+{
+ rtx dest_addr, insn;
+ int bb;
+
+ while (GET_CODE (dest) == SUBREG
+ || GET_CODE (dest) == ZERO_EXTRACT
+ || GET_CODE (dest) == STRICT_LOW_PART)
+ dest = XEXP (dest, 0);
+
+ /* If DEST is not a MEM, then it will not conflict with a load. Note
+ that function calls are assumed to clobber memory, but are handled
+ elsewhere. */
+
+ if (! MEM_P (dest))
+ return;
+
+ dest_addr = get_addr (XEXP (dest, 0));
+ dest_addr = canon_rtx (dest_addr);
+ insn = (rtx) v_insn;
+ bb = BLOCK_FOR_INSN (insn)->index;
+
+ canon_modify_mem_list[bb] =
+ alloc_EXPR_LIST (VOIDmode, dest_addr, canon_modify_mem_list[bb]);
+ canon_modify_mem_list[bb] =
+ alloc_EXPR_LIST (VOIDmode, dest, canon_modify_mem_list[bb]);
+}
+
+/* Record memory modification information for INSN. We do not actually care
+ about the memory location(s) that are set, or even how they are set (consider
+ a CALL_INSN). We merely need to record which insns modify memory. */
+
+static void
+record_last_mem_set_info (rtx insn)
+{
+ int bb = BLOCK_FOR_INSN (insn)->index;
+
+ /* load_killed_in_block_p will handle the case of calls clobbering
+ everything. */
+ modify_mem_list[bb] = alloc_INSN_LIST (insn, modify_mem_list[bb]);
+ bitmap_set_bit (modify_mem_list_set, bb);
+
+ if (CALL_P (insn))
+ {
+ /* Note that traversals of this loop (other than for free-ing)
+ will break after encountering a CALL_INSN. So, there's no
+ need to insert a pair of items, as canon_list_insert does. */
+ canon_modify_mem_list[bb] =
+ alloc_INSN_LIST (insn, canon_modify_mem_list[bb]);
+ bitmap_set_bit (blocks_with_calls, bb);
+ }
+ else
+ note_stores (PATTERN (insn), canon_list_insert, (void*) insn);
+}
+
+/* Called from compute_hash_table via note_stores to handle one
+ SET or CLOBBER in an insn. DATA is really the instruction in which
+ the SET is taking place. */
+
+static void
+record_last_set_info (rtx dest, const_rtx setter ATTRIBUTE_UNUSED, void *data)
+{
+ rtx last_set_insn = (rtx) data;
+
+ if (GET_CODE (dest) == SUBREG)
+ dest = SUBREG_REG (dest);
+
+ if (REG_P (dest))
+ record_last_reg_set_info (last_set_insn, REGNO (dest));
+ else if (MEM_P (dest)
+ /* Ignore pushes, they clobber nothing. */
+ && ! push_operand (dest, GET_MODE (dest)))
+ record_last_mem_set_info (last_set_insn);
+}
+
+/* Top level function to create an expression or assignment hash table.
+
+ Expression entries are placed in the hash table if
+ - they are of the form (set (pseudo-reg) src),
+ - src is something we want to perform GCSE on,
+ - none of the operands are subsequently modified in the block
+
+ Assignment entries are placed in the hash table if
+ - they are of the form (set (pseudo-reg) src),
+ - src is something we want to perform const/copy propagation on,
+ - none of the operands or target are subsequently modified in the block
+
+ Currently src must be a pseudo-reg or a const_int.
+
+ TABLE is the table computed. */
+
+static void
+compute_hash_table_work (struct hash_table_d *table)
+{
+ int i;
+
+ /* re-Cache any INSN_LIST nodes we have allocated. */
+ clear_modify_mem_tables ();
+ /* Some working arrays used to track first and last set in each block. */
+ reg_avail_info = GNEWVEC (struct reg_avail_info, max_reg_num ());
+
+ for (i = 0; i < max_reg_num (); ++i)
+ reg_avail_info[i].last_bb = NULL;
+
+ FOR_EACH_BB (current_bb)
+ {
+ rtx insn;
+ unsigned int regno;
+
+ /* First pass over the instructions records information used to
+ determine when registers and memory are first and last set. */
+ FOR_BB_INSNS (current_bb, insn)
+ {
+ if (!NONDEBUG_INSN_P (insn))
+ continue;
+
+ if (CALL_P (insn))
+ {
+ for (regno = 0; regno < FIRST_PSEUDO_REGISTER; regno++)
+ if (TEST_HARD_REG_BIT (regs_invalidated_by_call, regno))
+ record_last_reg_set_info (insn, regno);
+
+ mark_call (insn);
+ }
+
+ note_stores (PATTERN (insn), record_last_set_info, insn);
+ }
+
+ /* Insert implicit sets in the hash table. */
+ if (table->set_p
+ && implicit_sets[current_bb->index] != NULL_RTX)
+ hash_scan_set (implicit_sets[current_bb->index],
+ BB_HEAD (current_bb), table);
+
+ /* The next pass builds the hash table. */
+ FOR_BB_INSNS (current_bb, insn)
+ if (NONDEBUG_INSN_P (insn))
+ hash_scan_insn (insn, table);
+ }
+
+ free (reg_avail_info);
+ reg_avail_info = NULL;
+}
+
+/* Allocate space for the set/expr hash TABLE.
+ It is used to determine the number of buckets to use.
+ SET_P determines whether set or expression table will
+ be created. */
+
+static void
+alloc_hash_table (struct hash_table_d *table, int set_p)
+{
+ int n;
+
+ n = get_max_insn_count ();
+
+ table->size = n / 4;
+ if (table->size < 11)
+ table->size = 11;
+
+ /* Attempt to maintain efficient use of hash table.
+ Making it an odd number is simplest for now.
+ ??? Later take some measurements. */
+ table->size |= 1;
+ n = table->size * sizeof (struct expr *);
+ table->table = GNEWVAR (struct expr *, n);
+ table->set_p = set_p;
+}
+
+/* Free things allocated by alloc_hash_table. */
+
+static void
+free_hash_table (struct hash_table_d *table)
+{
+ free (table->table);
+}
+
+/* Compute the hash TABLE for doing copy/const propagation or
+ expression hash table. */
+
+static void
+compute_hash_table (struct hash_table_d *table)
+{
+ /* Initialize count of number of entries in hash table. */
+ table->n_elems = 0;
+ memset (table->table, 0, table->size * sizeof (struct expr *));
+
+ compute_hash_table_work (table);
+}
+
+/* Expression tracking support. */
+
+/* Lookup REGNO in the set TABLE. The result is a pointer to the
+ table entry, or NULL if not found. */
+
+static struct expr *
+lookup_set (unsigned int regno, struct hash_table_d *table)
+{
+ unsigned int hash = hash_set (regno, table->size);
+ struct expr *expr;
+
+ expr = table->table[hash];
+
+ while (expr && REGNO (SET_DEST (expr->expr)) != regno)
+ expr = expr->next_same_hash;
+
+ return expr;
+}
+
+/* Return the next entry for REGNO in list EXPR. */
+
+static struct expr *
+next_set (unsigned int regno, struct expr *expr)
+{
+ do
+ expr = expr->next_same_hash;
+ while (expr && REGNO (SET_DEST (expr->expr)) != regno);
+
+ return expr;
+}
+
+/* Like free_INSN_LIST_list or free_EXPR_LIST_list, except that the node
+ types may be mixed. */
+
+static void
+free_insn_expr_list_list (rtx *listp)
+{
+ rtx list, next;
+
+ for (list = *listp; list ; list = next)
+ {
+ next = XEXP (list, 1);
+ if (GET_CODE (list) == EXPR_LIST)
+ free_EXPR_LIST_node (list);
+ else
+ free_INSN_LIST_node (list);
+ }
+
+ *listp = NULL;
+}
+
+/* Clear canon_modify_mem_list and modify_mem_list tables. */
+static void
+clear_modify_mem_tables (void)
+{
+ unsigned i;
+ bitmap_iterator bi;
+
+ EXECUTE_IF_SET_IN_BITMAP (modify_mem_list_set, 0, i, bi)
+ {
+ free_INSN_LIST_list (modify_mem_list + i);
+ free_insn_expr_list_list (canon_modify_mem_list + i);
+ }
+ bitmap_clear (modify_mem_list_set);
+ bitmap_clear (blocks_with_calls);
+}
+
+/* Release memory used by modify_mem_list_set. */
+
+static void
+free_modify_mem_tables (void)
+{
+ clear_modify_mem_tables ();
+ free (modify_mem_list);
+ free (canon_modify_mem_list);
+ modify_mem_list = 0;
+ canon_modify_mem_list = 0;
+}
+
+/* Reset tables used to keep track of what's still available [since the
+ start of the block]. */
+
+static void
+reset_opr_set_tables (void)
+{
+ /* Maintain a bitmap of which regs have been set since beginning of
+ the block. */
+ CLEAR_REG_SET (reg_set_bitmap);
+
+ /* Also keep a record of the last instruction to modify memory.
+ For now this is very trivial, we only record whether any memory
+ location has been modified. */
+ clear_modify_mem_tables ();
+}
+
+/* Return nonzero if the operands of X are not set before INSN in
+ INSN's basic block. */
+
+static int
+oprs_not_set_p (const_rtx x, const_rtx insn)
+{
+ int i, j;
+ enum rtx_code code;
+ const char *fmt;
+
+ if (x == 0)
+ return 1;
+
+ code = GET_CODE (x);
+ switch (code)
+ {
+ case PC:
+ case CC0:
+ case CONST:
+ case CONST_INT:
+ case CONST_DOUBLE:
+ case CONST_FIXED:
+ case CONST_VECTOR:
+ case SYMBOL_REF:
+ case LABEL_REF:
+ case ADDR_VEC:
+ case ADDR_DIFF_VEC:
+ return 1;
+
+ case MEM:
+ if (load_killed_in_block_p (BLOCK_FOR_INSN (insn),
+ DF_INSN_LUID (insn), x, 0))
+ return 0;
+ else
+ return oprs_not_set_p (XEXP (x, 0), insn);
+
+ case REG:
+ return ! REGNO_REG_SET_P (reg_set_bitmap, REGNO (x));
+
+ default:
+ break;
+ }
+
+ for (i = GET_RTX_LENGTH (code) - 1, fmt = GET_RTX_FORMAT (code); i >= 0; i--)
+ {
+ if (fmt[i] == 'e')
+ {
+ /* If we are about to do the last recursive call
+ needed at this level, change it into iteration.
+ This function is called enough to be worth it. */
+ if (i == 0)
+ return oprs_not_set_p (XEXP (x, i), insn);
+
+ if (! oprs_not_set_p (XEXP (x, i), insn))
+ return 0;
+ }
+ else if (fmt[i] == 'E')
+ for (j = 0; j < XVECLEN (x, i); j++)
+ if (! oprs_not_set_p (XVECEXP (x, i, j), insn))
+ return 0;
+ }
+
+ return 1;
+}
+
+/* Mark things set by a CALL. */
+
+static void
+mark_call (rtx insn)
+{
+ if (! RTL_CONST_OR_PURE_CALL_P (insn))
+ record_last_mem_set_info (insn);
+}
+
+/* Mark things set by a SET. */
+
+static void
+mark_set (rtx pat, rtx insn)
+{
+ rtx dest = SET_DEST (pat);
+
+ while (GET_CODE (dest) == SUBREG
+ || GET_CODE (dest) == ZERO_EXTRACT
+ || GET_CODE (dest) == STRICT_LOW_PART)
+ dest = XEXP (dest, 0);
+
+ if (REG_P (dest))
+ SET_REGNO_REG_SET (reg_set_bitmap, REGNO (dest));
+ else if (MEM_P (dest))
+ record_last_mem_set_info (insn);
+
+ if (GET_CODE (SET_SRC (pat)) == CALL)
+ mark_call (insn);
+}
+
+/* Record things set by a CLOBBER. */
+
+static void
+mark_clobber (rtx pat, rtx insn)
+{
+ rtx clob = XEXP (pat, 0);
+
+ while (GET_CODE (clob) == SUBREG || GET_CODE (clob) == STRICT_LOW_PART)
+ clob = XEXP (clob, 0);
+
+ if (REG_P (clob))
+ SET_REGNO_REG_SET (reg_set_bitmap, REGNO (clob));
+ else
+ record_last_mem_set_info (insn);
+}
+
+/* Record things set by INSN.
+ This data is used by oprs_not_set_p. */
+
+static void
+mark_oprs_set (rtx insn)
+{
+ rtx pat = PATTERN (insn);
+ int i;
+
+ if (GET_CODE (pat) == SET)
+ mark_set (pat, insn);
+ else if (GET_CODE (pat) == PARALLEL)
+ for (i = 0; i < XVECLEN (pat, 0); i++)
+ {
+ rtx x = XVECEXP (pat, 0, i);
+
+ if (GET_CODE (x) == SET)
+ mark_set (x, insn);
+ else if (GET_CODE (x) == CLOBBER)
+ mark_clobber (x, insn);
+ else if (GET_CODE (x) == CALL)
+ mark_call (insn);
+ }
+
+ else if (GET_CODE (pat) == CLOBBER)
+ mark_clobber (pat, insn);
+ else if (GET_CODE (pat) == CALL)
+ mark_call (insn);
+}
+
+
+/* Compute copy/constant propagation working variables. */
+
+/* Local properties of assignments. */
+static sbitmap *cprop_pavloc;
+static sbitmap *cprop_absaltered;
+
+/* Global properties of assignments (computed from the local properties). */
+static sbitmap *cprop_avin;
+static sbitmap *cprop_avout;
+
+/* Allocate vars used for copy/const propagation. N_BLOCKS is the number of
+ basic blocks. N_SETS is the number of sets. */
+
+static void
+alloc_cprop_mem (int n_blocks, int n_sets)
+{
+ cprop_pavloc = sbitmap_vector_alloc (n_blocks, n_sets);
+ cprop_absaltered = sbitmap_vector_alloc (n_blocks, n_sets);
+
+ cprop_avin = sbitmap_vector_alloc (n_blocks, n_sets);
+ cprop_avout = sbitmap_vector_alloc (n_blocks, n_sets);
+}
+
+/* Free vars used by copy/const propagation. */
+
+static void
+free_cprop_mem (void)
+{
+ sbitmap_vector_free (cprop_pavloc);
+ sbitmap_vector_free (cprop_absaltered);
+ sbitmap_vector_free (cprop_avin);
+ sbitmap_vector_free (cprop_avout);
+}
+
+/* For each block, compute whether X is transparent. X is either an
+ expression or an assignment [though we don't care which, for this context
+ an assignment is treated as an expression]. For each block where an
+ element of X is modified, set (SET_P == 1) or reset (SET_P == 0) the INDX
+ bit in BMAP. */
+
+static void
+compute_transp (const_rtx x, int indx, sbitmap *bmap, int set_p)
+{
+ int i, j;
+ enum rtx_code code;
+ const char *fmt;
+
+ /* repeat is used to turn tail-recursion into iteration since GCC
+ can't do it when there's no return value. */
+ repeat:
+
+ if (x == 0)
+ return;
+
+ code = GET_CODE (x);
+ switch (code)
+ {
+ case REG:
+ if (set_p)
+ {
+ df_ref def;
+ for (def = DF_REG_DEF_CHAIN (REGNO (x));
+ def;
+ def = DF_REF_NEXT_REG (def))
+ SET_BIT (bmap[DF_REF_BB (def)->index], indx);
+ }
+ else
+ {
+ df_ref def;
+ for (def = DF_REG_DEF_CHAIN (REGNO (x));
+ def;
+ def = DF_REF_NEXT_REG (def))
+ RESET_BIT (bmap[DF_REF_BB (def)->index], indx);
+ }
+
+ return;
+
+ case MEM:
+ if (! MEM_READONLY_P (x))
+ {
+ bitmap_iterator bi;
+ unsigned bb_index;
+
+ /* First handle all the blocks with calls. We don't need to
+ do any list walking for them. */
+ EXECUTE_IF_SET_IN_BITMAP (blocks_with_calls, 0, bb_index, bi)
+ {
+ if (set_p)
+ SET_BIT (bmap[bb_index], indx);
+ else
+ RESET_BIT (bmap[bb_index], indx);
+ }
+
+ /* Now iterate over the blocks which have memory modifications
+ but which do not have any calls. */
+ EXECUTE_IF_AND_COMPL_IN_BITMAP (modify_mem_list_set,
+ blocks_with_calls,
+ 0, bb_index, bi)
+ {
+ rtx list_entry = canon_modify_mem_list[bb_index];
+
+ while (list_entry)
+ {
+ rtx dest, dest_addr;
+
+ /* LIST_ENTRY must be an INSN of some kind that sets memory.
+ Examine each hunk of memory that is modified. */
+
+ dest = XEXP (list_entry, 0);
+ list_entry = XEXP (list_entry, 1);
+ dest_addr = XEXP (list_entry, 0);
+
+ if (canon_true_dependence (dest, GET_MODE (dest), dest_addr,
+ x, NULL_RTX, rtx_addr_varies_p))
+ {
+ if (set_p)
+ SET_BIT (bmap[bb_index], indx);
+ else
+ RESET_BIT (bmap[bb_index], indx);
+ break;
+ }
+ list_entry = XEXP (list_entry, 1);
+ }
+ }
+ }
+
+ x = XEXP (x, 0);
+ goto repeat;
+
+ case PC:
+ case CC0: /*FIXME*/
+ case CONST:
+ case CONST_INT:
+ case CONST_DOUBLE:
+ case CONST_FIXED:
+ case CONST_VECTOR:
+ case SYMBOL_REF:
+ case LABEL_REF:
+ case ADDR_VEC:
+ case ADDR_DIFF_VEC:
+ return;
+
+ default:
+ break;
+ }
+
+ for (i = GET_RTX_LENGTH (code) - 1, fmt = GET_RTX_FORMAT (code); i >= 0; i--)
+ {
+ if (fmt[i] == 'e')
+ {
+ /* If we are about to do the last recursive call
+ needed at this level, change it into iteration.
+ This function is called enough to be worth it. */
+ if (i == 0)
+ {
+ x = XEXP (x, i);
+ goto repeat;
+ }
+
+ compute_transp (XEXP (x, i), indx, bmap, set_p);
+ }
+ else if (fmt[i] == 'E')
+ for (j = 0; j < XVECLEN (x, i); j++)
+ compute_transp (XVECEXP (x, i, j), indx, bmap, set_p);
+ }
+}
+
+/* Top level routine to do the dataflow analysis needed by copy/const
+ propagation. */
+
+static void
+compute_cprop_data (void)
+{
+ compute_local_properties (cprop_absaltered, cprop_pavloc, NULL, &set_hash_table);
+ compute_available (cprop_pavloc, cprop_absaltered,
+ cprop_avout, cprop_avin);
+}
+
+/* Copy/constant propagation. */
+
+/* Maximum number of register uses in an insn that we handle. */
+#define MAX_USES 8
+
+/* Table of uses found in an insn.
+ Allocated statically to avoid alloc/free complexity and overhead. */
+static struct reg_use reg_use_table[MAX_USES];
+
+/* Index into `reg_use_table' while building it. */
+static int reg_use_count;
+
+/* Set up a list of register numbers used in INSN. The found uses are stored
+ in `reg_use_table'. `reg_use_count' is initialized to zero before entry,
+ and contains the number of uses in the table upon exit.
+
+ ??? If a register appears multiple times we will record it multiple times.
+ This doesn't hurt anything but it will slow things down. */
+
+static void
+find_used_regs (rtx *xptr, void *data ATTRIBUTE_UNUSED)
+{
+ int i, j;
+ enum rtx_code code;
+ const char *fmt;
+ rtx x = *xptr;
+
+ /* repeat is used to turn tail-recursion into iteration since GCC
+ can't do it when there's no return value. */
+ repeat:
+ if (x == 0)
+ return;
+
+ code = GET_CODE (x);
+ if (REG_P (x))
+ {
+ if (reg_use_count == MAX_USES)
+ return;
+
+ reg_use_table[reg_use_count].reg_rtx = x;
+ reg_use_count++;
+ }
+
+ /* Recursively scan the operands of this expression. */
+
+ for (i = GET_RTX_LENGTH (code) - 1, fmt = GET_RTX_FORMAT (code); i >= 0; i--)
+ {
+ if (fmt[i] == 'e')
+ {
+ /* If we are about to do the last recursive call
+ needed at this level, change it into iteration.
+ This function is called enough to be worth it. */
+ if (i == 0)
+ {
+ x = XEXP (x, 0);
+ goto repeat;
+ }
+
+ find_used_regs (&XEXP (x, i), data);
+ }
+ else if (fmt[i] == 'E')
+ for (j = 0; j < XVECLEN (x, i); j++)
+ find_used_regs (&XVECEXP (x, i, j), data);
+ }
+}
+
+/* Try to replace all non-SET_DEST occurrences of FROM in INSN with TO.
+ Returns nonzero is successful. */
+
+static int
+try_replace_reg (rtx from, rtx to, rtx insn)
+{
+ rtx note = find_reg_equal_equiv_note (insn);
+ rtx src = 0;
+ int success = 0;
+ rtx set = single_set (insn);
+
+ /* Usually we substitute easy stuff, so we won't copy everything.
+ We however need to take care to not duplicate non-trivial CONST
+ expressions. */
+ to = copy_rtx (to);
+
+ validate_replace_src_group (from, to, insn);
+ if (num_changes_pending () && apply_change_group ())
+ success = 1;
+
+ /* Try to simplify SET_SRC if we have substituted a constant. */
+ if (success && set && CONSTANT_P (to))
+ {
+ src = simplify_rtx (SET_SRC (set));
+
+ if (src)
+ validate_change (insn, &SET_SRC (set), src, 0);
+ }
+
+ /* If there is already a REG_EQUAL note, update the expression in it
+ with our replacement. */
+ if (note != 0 && REG_NOTE_KIND (note) == REG_EQUAL)
+ set_unique_reg_note (insn, REG_EQUAL,
+ simplify_replace_rtx (XEXP (note, 0), from, to));
+ if (!success && set && reg_mentioned_p (from, SET_SRC (set)))
+ {
+ /* If above failed and this is a single set, try to simplify the source of
+ the set given our substitution. We could perhaps try this for multiple
+ SETs, but it probably won't buy us anything. */
+ src = simplify_replace_rtx (SET_SRC (set), from, to);
+
+ if (!rtx_equal_p (src, SET_SRC (set))
+ && validate_change (insn, &SET_SRC (set), src, 0))
+ success = 1;
+
+ /* If we've failed perform the replacement, have a single SET to
+ a REG destination and don't yet have a note, add a REG_EQUAL note
+ to not lose information. */
+ if (!success && note == 0 && set != 0 && REG_P (SET_DEST (set)))
+ note = set_unique_reg_note (insn, REG_EQUAL, copy_rtx (src));
+ }
+
+ /* REG_EQUAL may get simplified into register.
+ We don't allow that. Remove that note. This code ought
+ not to happen, because previous code ought to synthesize
+ reg-reg move, but be on the safe side. */
+ if (note && REG_NOTE_KIND (note) == REG_EQUAL && REG_P (XEXP (note, 0)))
+ remove_note (insn, note);
+
+ return success;
+}
+
+/* Find a set of REGNOs that are available on entry to INSN's block. Returns
+ NULL no such set is found. */
+
+static struct expr *
+find_avail_set (int regno, rtx insn)
+{
+ /* SET1 contains the last set found that can be returned to the caller for
+ use in a substitution. */
+ struct expr *set1 = 0;
+
+ /* Loops are not possible here. To get a loop we would need two sets
+ available at the start of the block containing INSN. i.e. we would
+ need two sets like this available at the start of the block:
+
+ (set (reg X) (reg Y))
+ (set (reg Y) (reg X))
+
+ This can not happen since the set of (reg Y) would have killed the
+ set of (reg X) making it unavailable at the start of this block. */
+ while (1)
+ {
+ rtx src;
+ struct expr *set = lookup_set (regno, &set_hash_table);
+
+ /* Find a set that is available at the start of the block
+ which contains INSN. */
+ while (set)
+ {
+ if (TEST_BIT (cprop_avin[BLOCK_FOR_INSN (insn)->index],
+ set->bitmap_index))
+ break;
+ set = next_set (regno, set);
+ }
+
+ /* If no available set was found we've reached the end of the
+ (possibly empty) copy chain. */
+ if (set == 0)
+ break;
+
+ gcc_assert (GET_CODE (set->expr) == SET);
+
+ src = SET_SRC (set->expr);
+
+ /* We know the set is available.
+ Now check that SRC is ANTLOC (i.e. none of the source operands
+ have changed since the start of the block).
+
+ If the source operand changed, we may still use it for the next
+ iteration of this loop, but we may not use it for substitutions. */
+
+ if (gcse_constant_p (src) || oprs_not_set_p (src, insn))
+ set1 = set;
+
+ /* If the source of the set is anything except a register, then
+ we have reached the end of the copy chain. */
+ if (! REG_P (src))
+ break;
+
+ /* Follow the copy chain, i.e. start another iteration of the loop
+ and see if we have an available copy into SRC. */
+ regno = REGNO (src);
+ }
+
+ /* SET1 holds the last set that was available and anticipatable at
+ INSN. */
+ return set1;
+}
+
+/* Subroutine of cprop_insn that tries to propagate constants into
+ JUMP_INSNS. JUMP must be a conditional jump. If SETCC is non-NULL
+ it is the instruction that immediately precedes JUMP, and must be a
+ single SET of a register. FROM is what we will try to replace,
+ SRC is the constant we will try to substitute for it. Returns nonzero
+ if a change was made. */
+
+static int
+cprop_jump (basic_block bb, rtx setcc, rtx jump, rtx from, rtx src)
+{
+ rtx new_rtx, set_src, note_src;
+ rtx set = pc_set (jump);
+ rtx note = find_reg_equal_equiv_note (jump);
+
+ if (note)
+ {
+ note_src = XEXP (note, 0);
+ if (GET_CODE (note_src) == EXPR_LIST)
+ note_src = NULL_RTX;
+ }
+ else note_src = NULL_RTX;
+
+ /* Prefer REG_EQUAL notes except those containing EXPR_LISTs. */
+ set_src = note_src ? note_src : SET_SRC (set);
+
+ /* First substitute the SETCC condition into the JUMP instruction,
+ then substitute that given values into this expanded JUMP. */
+ if (setcc != NULL_RTX
+ && !modified_between_p (from, setcc, jump)
+ && !modified_between_p (src, setcc, jump))
+ {
+ rtx setcc_src;
+ rtx setcc_set = single_set (setcc);
+ rtx setcc_note = find_reg_equal_equiv_note (setcc);
+ setcc_src = (setcc_note && GET_CODE (XEXP (setcc_note, 0)) != EXPR_LIST)
+ ? XEXP (setcc_note, 0) : SET_SRC (setcc_set);
+ set_src = simplify_replace_rtx (set_src, SET_DEST (setcc_set),
+ setcc_src);
+ }
+ else
+ setcc = NULL_RTX;
+
+ new_rtx = simplify_replace_rtx (set_src, from, src);
+
+ /* If no simplification can be made, then try the next register. */
+ if (rtx_equal_p (new_rtx, SET_SRC (set)))
+ return 0;
+
+ /* If this is now a no-op delete it, otherwise this must be a valid insn. */
+ if (new_rtx == pc_rtx)
+ delete_insn (jump);
+ else
+ {
+ /* Ensure the value computed inside the jump insn to be equivalent
+ to one computed by setcc. */
+ if (setcc && modified_in_p (new_rtx, setcc))
+ return 0;
+ if (! validate_unshare_change (jump, &SET_SRC (set), new_rtx, 0))
+ {
+ /* When (some) constants are not valid in a comparison, and there
+ are two registers to be replaced by constants before the entire
+ comparison can be folded into a constant, we need to keep
+ intermediate information in REG_EQUAL notes. For targets with
+ separate compare insns, such notes are added by try_replace_reg.
+ When we have a combined compare-and-branch instruction, however,
+ we need to attach a note to the branch itself to make this
+ optimization work. */
+
+ if (!rtx_equal_p (new_rtx, note_src))
+ set_unique_reg_note (jump, REG_EQUAL, copy_rtx (new_rtx));
+ return 0;
+ }
+
+ /* Remove REG_EQUAL note after simplification. */
+ if (note_src)
+ remove_note (jump, note);
+ }
+
+#ifdef HAVE_cc0
+ /* Delete the cc0 setter. */
+ if (setcc != NULL && CC0_P (SET_DEST (single_set (setcc))))
+ delete_insn (setcc);
+#endif
+
+ global_const_prop_count++;
+ if (dump_file != NULL)
+ {
+ fprintf (dump_file,
+ "GLOBAL CONST-PROP: Replacing reg %d in jump_insn %d with constant ",
+ REGNO (from), INSN_UID (jump));
+ print_rtl (dump_file, src);
+ fprintf (dump_file, "\n");
+ }
+ purge_dead_edges (bb);
+
+ /* If a conditional jump has been changed into unconditional jump, remove
+ the jump and make the edge fallthru - this is always called in
+ cfglayout mode. */
+ if (new_rtx != pc_rtx && simplejump_p (jump))
+ {
+ edge e;
+ edge_iterator ei;
+
+ for (ei = ei_start (bb->succs); (e = ei_safe_edge (ei)); ei_next (&ei))
+ if (e->dest != EXIT_BLOCK_PTR
+ && BB_HEAD (e->dest) == JUMP_LABEL (jump))
+ {
+ e->flags |= EDGE_FALLTHRU;
+ break;
+ }
+ delete_insn (jump);
+ }
+
+ return 1;
+}
+
+static bool
+constprop_register (rtx insn, rtx from, rtx to)
+{
+ rtx sset;
+
+ /* Check for reg or cc0 setting instructions followed by
+ conditional branch instructions first. */
+ if ((sset = single_set (insn)) != NULL
+ && NEXT_INSN (insn)
+ && any_condjump_p (NEXT_INSN (insn)) && onlyjump_p (NEXT_INSN (insn)))
+ {
+ rtx dest = SET_DEST (sset);
+ if ((REG_P (dest) || CC0_P (dest))
+ && cprop_jump (BLOCK_FOR_INSN (insn), insn, NEXT_INSN (insn), from, to))
+ return 1;
+ }
+
+ /* Handle normal insns next. */
+ if (NONJUMP_INSN_P (insn)
+ && try_replace_reg (from, to, insn))
+ return 1;
+
+ /* Try to propagate a CONST_INT into a conditional jump.
+ We're pretty specific about what we will handle in this
+ code, we can extend this as necessary over time.
+
+ Right now the insn in question must look like
+ (set (pc) (if_then_else ...)) */
+ else if (any_condjump_p (insn) && onlyjump_p (insn))
+ return cprop_jump (BLOCK_FOR_INSN (insn), NULL, insn, from, to);
+ return 0;
+}
+
+/* Perform constant and copy propagation on INSN.
+ The result is nonzero if a change was made. */
+
+static int
+cprop_insn (rtx insn)
+{
+ struct reg_use *reg_used;
+ int changed = 0;
+ rtx note;
+
+ if (!INSN_P (insn))
+ return 0;
+
+ reg_use_count = 0;
+ note_uses (&PATTERN (insn), find_used_regs, NULL);
+
+ note = find_reg_equal_equiv_note (insn);
+
+ /* We may win even when propagating constants into notes. */
+ if (note)
+ find_used_regs (&XEXP (note, 0), NULL);
+
+ for (reg_used = &reg_use_table[0]; reg_use_count > 0;
+ reg_used++, reg_use_count--)
+ {
+ unsigned int regno = REGNO (reg_used->reg_rtx);
+ rtx pat, src;
+ struct expr *set;
+
+ /* If the register has already been set in this block, there's
+ nothing we can do. */
+ if (! oprs_not_set_p (reg_used->reg_rtx, insn))
+ continue;
+
+ /* Find an assignment that sets reg_used and is available
+ at the start of the block. */
+ set = find_avail_set (regno, insn);
+ if (! set)
+ continue;
+
+ pat = set->expr;
+ /* ??? We might be able to handle PARALLELs. Later. */
+ gcc_assert (GET_CODE (pat) == SET);
+
+ src = SET_SRC (pat);
+
+ /* Constant propagation. */
+ if (gcse_constant_p (src))
+ {
+ if (constprop_register (insn, reg_used->reg_rtx, src))
+ {
+ changed = 1;
+ global_const_prop_count++;
+ if (dump_file != NULL)
+ {
+ fprintf (dump_file, "GLOBAL CONST-PROP: Replacing reg %d in ", regno);
+ fprintf (dump_file, "insn %d with constant ", INSN_UID (insn));
+ print_rtl (dump_file, src);
+ fprintf (dump_file, "\n");
+ }
+ if (INSN_DELETED_P (insn))
+ return 1;
+ }
+ }
+ else if (REG_P (src)
+ && REGNO (src) >= FIRST_PSEUDO_REGISTER
+ && REGNO (src) != regno)
+ {
+ if (try_replace_reg (reg_used->reg_rtx, src, insn))
+ {
+ changed = 1;
+ global_copy_prop_count++;
+ if (dump_file != NULL)
+ {
+ fprintf (dump_file, "GLOBAL COPY-PROP: Replacing reg %d in insn %d",
+ regno, INSN_UID (insn));
+ fprintf (dump_file, " with reg %d\n", REGNO (src));
+ }
+
+ /* The original insn setting reg_used may or may not now be
+ deletable. We leave the deletion to flow. */
+ /* FIXME: If it turns out that the insn isn't deletable,
+ then we may have unnecessarily extended register lifetimes
+ and made things worse. */
+ }
+ }
+ }
+
+ if (changed && DEBUG_INSN_P (insn))
+ return 0;
+
+ return changed;
+}
+
+/* Like find_used_regs, but avoid recording uses that appear in
+ input-output contexts such as zero_extract or pre_dec. This
+ restricts the cases we consider to those for which local cprop
+ can legitimately make replacements. */
+
+static void
+local_cprop_find_used_regs (rtx *xptr, void *data)
+{
+ rtx x = *xptr;
+
+ if (x == 0)
+ return;
+
+ switch (GET_CODE (x))
+ {
+ case ZERO_EXTRACT:
+ case SIGN_EXTRACT:
+ case STRICT_LOW_PART:
+ return;
+
+ case PRE_DEC:
+ case PRE_INC:
+ case POST_DEC:
+ case POST_INC:
+ case PRE_MODIFY:
+ case POST_MODIFY:
+ /* Can only legitimately appear this early in the context of
+ stack pushes for function arguments, but handle all of the
+ codes nonetheless. */
+ return;
+
+ case SUBREG:
+ /* Setting a subreg of a register larger than word_mode leaves
+ the non-written words unchanged. */
+ if (GET_MODE_BITSIZE (GET_MODE (SUBREG_REG (x))) > BITS_PER_WORD)
+ return;
+ break;
+
+ default:
+ break;
+ }
+
+ find_used_regs (xptr, data);
+}
+
+/* Try to perform local const/copy propagation on X in INSN. */
+
+static bool
+do_local_cprop (rtx x, rtx insn)
+{
+ rtx newreg = NULL, newcnst = NULL;
+
+ /* Rule out USE instructions and ASM statements as we don't want to
+ change the hard registers mentioned. */
+ if (REG_P (x)
+ && (REGNO (x) >= FIRST_PSEUDO_REGISTER
+ || (GET_CODE (PATTERN (insn)) != USE
+ && asm_noperands (PATTERN (insn)) < 0)))
+ {
+ cselib_val *val = cselib_lookup (x, GET_MODE (x), 0, VOIDmode);
+ struct elt_loc_list *l;
+
+ if (!val)
+ return false;
+ for (l = val->locs; l; l = l->next)
+ {
+ rtx this_rtx = l->loc;
+ rtx note;
+
+ if (gcse_constant_p (this_rtx))
+ newcnst = this_rtx;
+ if (REG_P (this_rtx) && REGNO (this_rtx) >= FIRST_PSEUDO_REGISTER
+ /* Don't copy propagate if it has attached REG_EQUIV note.
+ At this point this only function parameters should have
+ REG_EQUIV notes and if the argument slot is used somewhere
+ explicitly, it means address of parameter has been taken,
+ so we should not extend the lifetime of the pseudo. */
+ && (!(note = find_reg_note (l->setting_insn, REG_EQUIV, NULL_RTX))
+ || ! MEM_P (XEXP (note, 0))))
+ newreg = this_rtx;
+ }
+ if (newcnst && constprop_register (insn, x, newcnst))
+ {
+ if (dump_file != NULL)
+ {
+ fprintf (dump_file, "LOCAL CONST-PROP: Replacing reg %d in ",
+ REGNO (x));
+ fprintf (dump_file, "insn %d with constant ",
+ INSN_UID (insn));
+ print_rtl (dump_file, newcnst);
+ fprintf (dump_file, "\n");
+ }
+ local_const_prop_count++;
+ return true;
+ }
+ else if (newreg && newreg != x && try_replace_reg (x, newreg, insn))
+ {
+ if (dump_file != NULL)
+ {
+ fprintf (dump_file,
+ "LOCAL COPY-PROP: Replacing reg %d in insn %d",
+ REGNO (x), INSN_UID (insn));
+ fprintf (dump_file, " with reg %d\n", REGNO (newreg));
+ }
+ local_copy_prop_count++;
+ return true;
+ }
+ }
+ return false;
+}
+
+/* Do local const/copy propagation (i.e. within each basic block). */
+
+static int
+local_cprop_pass (void)
+{
+ basic_block bb;
+ rtx insn;
+ struct reg_use *reg_used;
+ bool changed = false;
+
+ cselib_init (0);
+ FOR_EACH_BB (bb)
+ {
+ FOR_BB_INSNS (bb, insn)
+ {
+ if (INSN_P (insn))
+ {
+ rtx note = find_reg_equal_equiv_note (insn);
+ do
+ {
+ reg_use_count = 0;
+ note_uses (&PATTERN (insn), local_cprop_find_used_regs,
+ NULL);
+ if (note)
+ local_cprop_find_used_regs (&XEXP (note, 0), NULL);
+
+ for (reg_used = &reg_use_table[0]; reg_use_count > 0;
+ reg_used++, reg_use_count--)
+ {
+ if (do_local_cprop (reg_used->reg_rtx, insn))
+ {
+ changed = true;
+ break;
+ }
+ }
+ if (INSN_DELETED_P (insn))
+ break;
+ }
+ while (reg_use_count);
+ }
+ cselib_process_insn (insn);
+ }
+
+ /* Forget everything at the end of a basic block. */
+ cselib_clear_table ();
+ }
+
+ cselib_finish ();
+
+ return changed;
+}
+
+/* Similar to get_condition, only the resulting condition must be
+ valid at JUMP, instead of at EARLIEST.
+
+ This differs from noce_get_condition in ifcvt.c in that we prefer not to
+ settle for the condition variable in the jump instruction being integral.
+ We prefer to be able to record the value of a user variable, rather than
+ the value of a temporary used in a condition. This could be solved by
+ recording the value of *every* register scanned by canonicalize_condition,
+ but this would require some code reorganization. */
+
+rtx
+fis_get_condition (rtx jump)
+{
+ return get_condition (jump, NULL, false, true);
+}
+
+/* Check the comparison COND to see if we can safely form an implicit set from
+ it. COND is either an EQ or NE comparison. */
+
+static bool
+implicit_set_cond_p (const_rtx cond)
+{
+ const enum machine_mode mode = GET_MODE (XEXP (cond, 0));
+ const_rtx cst = XEXP (cond, 1);
+
+ /* We can't perform this optimization if either operand might be or might
+ contain a signed zero. */
+ if (HONOR_SIGNED_ZEROS (mode))
+ {
+ /* It is sufficient to check if CST is or contains a zero. We must
+ handle float, complex, and vector. If any subpart is a zero, then
+ the optimization can't be performed. */
+ /* ??? The complex and vector checks are not implemented yet. We just
+ always return zero for them. */
+ if (GET_CODE (cst) == CONST_DOUBLE)
+ {
+ REAL_VALUE_TYPE d;
+ REAL_VALUE_FROM_CONST_DOUBLE (d, cst);
+ if (REAL_VALUES_EQUAL (d, dconst0))
+ return 0;
+ }
+ else
+ return 0;
+ }
+
+ return gcse_constant_p (cst);
+}
+
+/* Find the implicit sets of a function. An "implicit set" is a constraint
+ on the value of a variable, implied by a conditional jump. For example,
+ following "if (x == 2)", the then branch may be optimized as though the
+ conditional performed an "explicit set", in this example, "x = 2". This
+ function records the set patterns that are implicit at the start of each
+ basic block.
+
+ FIXME: This would be more effective if critical edges are pre-split. As
+ it is now, we can't record implicit sets for blocks that have
+ critical successor edges. This results in missed optimizations
+ and in more (unnecessary) work in cfgcleanup.c:thread_jump(). */
+
+static void
+find_implicit_sets (void)
+{
+ basic_block bb, dest;
+ unsigned int count;
+ rtx cond, new_rtx;
+
+ count = 0;
+ FOR_EACH_BB (bb)
+ /* Check for more than one successor. */
+ if (EDGE_COUNT (bb->succs) > 1)
+ {
+ cond = fis_get_condition (BB_END (bb));
+
+ if (cond
+ && (GET_CODE (cond) == EQ || GET_CODE (cond) == NE)
+ && REG_P (XEXP (cond, 0))
+ && REGNO (XEXP (cond, 0)) >= FIRST_PSEUDO_REGISTER
+ && implicit_set_cond_p (cond))
+ {
+ dest = GET_CODE (cond) == EQ ? BRANCH_EDGE (bb)->dest
+ : FALLTHRU_EDGE (bb)->dest;
+
+ if (dest
+ /* Record nothing for a critical edge. */
+ && single_pred_p (dest)
+ && dest != EXIT_BLOCK_PTR)
+ {
+ new_rtx = gen_rtx_SET (VOIDmode, XEXP (cond, 0),
+ XEXP (cond, 1));
+ implicit_sets[dest->index] = new_rtx;
+ if (dump_file)
+ {
+ fprintf(dump_file, "Implicit set of reg %d in ",
+ REGNO (XEXP (cond, 0)));
+ fprintf(dump_file, "basic block %d\n", dest->index);
+ }
+ count++;
+ }
+ }
+ }
+
+ if (dump_file)
+ fprintf (dump_file, "Found %d implicit sets\n", count);
+}
+
+/* Bypass conditional jumps. */
+
+/* The value of last_basic_block at the beginning of the jump_bypass
+ pass. The use of redirect_edge_and_branch_force may introduce new
+ basic blocks, but the data flow analysis is only valid for basic
+ block indices less than bypass_last_basic_block. */
+
+static int bypass_last_basic_block;
+
+/* Find a set of REGNO to a constant that is available at the end of basic
+ block BB. Returns NULL if no such set is found. Based heavily upon
+ find_avail_set. */
+
+static struct expr *
+find_bypass_set (int regno, int bb)
+{
+ struct expr *result = 0;
+
+ for (;;)
+ {
+ rtx src;
+ struct expr *set = lookup_set (regno, &set_hash_table);
+
+ while (set)
+ {
+ if (TEST_BIT (cprop_avout[bb], set->bitmap_index))
+ break;
+ set = next_set (regno, set);
+ }
+
+ if (set == 0)
+ break;
+
+ gcc_assert (GET_CODE (set->expr) == SET);
+
+ src = SET_SRC (set->expr);
+ if (gcse_constant_p (src))
+ result = set;
+
+ if (! REG_P (src))
+ break;
+
+ regno = REGNO (src);
+ }
+ return result;
+}
+
+
+/* Subroutine of bypass_block that checks whether a pseudo is killed by
+ any of the instructions inserted on an edge. Jump bypassing places
+ condition code setters on CFG edges using insert_insn_on_edge. This
+ function is required to check that our data flow analysis is still
+ valid prior to commit_edge_insertions. */
+
+static bool
+reg_killed_on_edge (const_rtx reg, const_edge e)
+{
+ rtx insn;
+
+ for (insn = e->insns.r; insn; insn = NEXT_INSN (insn))
+ if (INSN_P (insn) && reg_set_p (reg, insn))
+ return true;
+
+ return false;
+}
+
+/* Subroutine of bypass_conditional_jumps that attempts to bypass the given
+ basic block BB which has more than one predecessor. If not NULL, SETCC
+ is the first instruction of BB, which is immediately followed by JUMP_INSN
+ JUMP. Otherwise, SETCC is NULL, and JUMP is the first insn of BB.
+ Returns nonzero if a change was made.
+
+ During the jump bypassing pass, we may place copies of SETCC instructions
+ on CFG edges. The following routine must be careful to pay attention to
+ these inserted insns when performing its transformations. */
+
+static int
+bypass_block (basic_block bb, rtx setcc, rtx jump)
+{
+ rtx insn, note;
+ edge e, edest;
+ int i, change;
+ int may_be_loop_header;
+ unsigned removed_p;
+ edge_iterator ei;
+
+ insn = (setcc != NULL) ? setcc : jump;
+
+ /* Determine set of register uses in INSN. */
+ reg_use_count = 0;
+ note_uses (&PATTERN (insn), find_used_regs, NULL);
+ note = find_reg_equal_equiv_note (insn);
+ if (note)
+ find_used_regs (&XEXP (note, 0), NULL);
+
+ may_be_loop_header = false;
+ FOR_EACH_EDGE (e, ei, bb->preds)
+ if (e->flags & EDGE_DFS_BACK)
+ {
+ may_be_loop_header = true;
+ break;
+ }
+
+ change = 0;
+ for (ei = ei_start (bb->preds); (e = ei_safe_edge (ei)); )
+ {
+ removed_p = 0;
+
+ if (e->flags & EDGE_COMPLEX)
+ {
+ ei_next (&ei);
+ continue;
+ }
+
+ /* We can't redirect edges from new basic blocks. */
+ if (e->src->index >= bypass_last_basic_block)
+ {
+ ei_next (&ei);
+ continue;
+ }
+
+ /* The irreducible loops created by redirecting of edges entering the
+ loop from outside would decrease effectiveness of some of the following
+ optimizations, so prevent this. */
+ if (may_be_loop_header
+ && !(e->flags & EDGE_DFS_BACK))
+ {
+ ei_next (&ei);
+ continue;
+ }
+
+ for (i = 0; i < reg_use_count; i++)
+ {
+ struct reg_use *reg_used = &reg_use_table[i];
+ unsigned int regno = REGNO (reg_used->reg_rtx);
+ basic_block dest, old_dest;
+ struct expr *set;
+ rtx src, new_rtx;
+
+ set = find_bypass_set (regno, e->src->index);
+
+ if (! set)
+ continue;
+
+ /* Check the data flow is valid after edge insertions. */
+ if (e->insns.r && reg_killed_on_edge (reg_used->reg_rtx, e))
+ continue;
+
+ src = SET_SRC (pc_set (jump));
+
+ if (setcc != NULL)
+ src = simplify_replace_rtx (src,
+ SET_DEST (PATTERN (setcc)),
+ SET_SRC (PATTERN (setcc)));
+
+ new_rtx = simplify_replace_rtx (src, reg_used->reg_rtx,
+ SET_SRC (set->expr));
+
+ /* Jump bypassing may have already placed instructions on
+ edges of the CFG. We can't bypass an outgoing edge that
+ has instructions associated with it, as these insns won't
+ get executed if the incoming edge is redirected. */
+
+ if (new_rtx == pc_rtx)
+ {
+ edest = FALLTHRU_EDGE (bb);
+ dest = edest->insns.r ? NULL : edest->dest;
+ }
+ else if (GET_CODE (new_rtx) == LABEL_REF)
+ {
+ dest = BLOCK_FOR_INSN (XEXP (new_rtx, 0));
+ /* Don't bypass edges containing instructions. */
+ edest = find_edge (bb, dest);
+ if (edest && edest->insns.r)
+ dest = NULL;
+ }
+ else
+ dest = NULL;
+
+ /* Avoid unification of the edge with other edges from original
+ branch. We would end up emitting the instruction on "both"
+ edges. */
+
+ if (dest && setcc && !CC0_P (SET_DEST (PATTERN (setcc)))
+ && find_edge (e->src, dest))
+ dest = NULL;
+
+ old_dest = e->dest;
+ if (dest != NULL
+ && dest != old_dest
+ && dest != EXIT_BLOCK_PTR)
+ {
+ redirect_edge_and_branch_force (e, dest);
+
+ /* Copy the register setter to the redirected edge.
+ Don't copy CC0 setters, as CC0 is dead after jump. */
+ if (setcc)
+ {
+ rtx pat = PATTERN (setcc);
+ if (!CC0_P (SET_DEST (pat)))
+ insert_insn_on_edge (copy_insn (pat), e);
+ }
+
+ if (dump_file != NULL)
+ {
+ fprintf (dump_file, "JUMP-BYPASS: Proved reg %d "
+ "in jump_insn %d equals constant ",
+ regno, INSN_UID (jump));
+ print_rtl (dump_file, SET_SRC (set->expr));
+ fprintf (dump_file, "\nBypass edge from %d->%d to %d\n",
+ e->src->index, old_dest->index, dest->index);
+ }
+ change = 1;
+ removed_p = 1;
+ break;
+ }
+ }
+ if (!removed_p)
+ ei_next (&ei);
+ }
+ return change;
+}
+
+/* Find basic blocks with more than one predecessor that only contain a
+ single conditional jump. If the result of the comparison is known at
+ compile-time from any incoming edge, redirect that edge to the
+ appropriate target. Returns nonzero if a change was made.
+
+ This function is now mis-named, because we also handle indirect jumps. */
+
+static int
+bypass_conditional_jumps (void)
+{
+ basic_block bb;
+ int changed;
+ rtx setcc;
+ rtx insn;
+ rtx dest;
+
+ /* Note we start at block 1. */
+ if (ENTRY_BLOCK_PTR->next_bb == EXIT_BLOCK_PTR)
+ return 0;
+
+ bypass_last_basic_block = last_basic_block;
+ mark_dfs_back_edges ();
+
+ changed = 0;
+ FOR_BB_BETWEEN (bb, ENTRY_BLOCK_PTR->next_bb->next_bb,
+ EXIT_BLOCK_PTR, next_bb)
+ {
+ /* Check for more than one predecessor. */
+ if (!single_pred_p (bb))
+ {
+ setcc = NULL_RTX;
+ FOR_BB_INSNS (bb, insn)
+ if (DEBUG_INSN_P (insn))
+ continue;
+ else if (NONJUMP_INSN_P (insn))
+ {
+ if (setcc)
+ break;
+ if (GET_CODE (PATTERN (insn)) != SET)
+ break;
+
+ dest = SET_DEST (PATTERN (insn));
+ if (REG_P (dest) || CC0_P (dest))
+ setcc = insn;
+ else
+ break;
+ }
+ else if (JUMP_P (insn))
+ {
+ if ((any_condjump_p (insn) || computed_jump_p (insn))
+ && onlyjump_p (insn))
+ changed |= bypass_block (bb, setcc, insn);
+ break;
+ }
+ else if (INSN_P (insn))
+ break;
+ }
+ }
+
+ /* If we bypassed any register setting insns, we inserted a
+ copy on the redirected edge. These need to be committed. */
+ if (changed)
+ commit_edge_insertions ();
+
+ return changed;
+}
+
+/* Compute PRE+LCM working variables. */
+
+/* Local properties of expressions. */
+/* Nonzero for expressions that are transparent in the block. */
+static sbitmap *transp;
+
+/* Nonzero for expressions that are computed (available) in the block. */
+static sbitmap *comp;
+
+/* Nonzero for expressions that are locally anticipatable in the block. */
+static sbitmap *antloc;
+
+/* Nonzero for expressions where this block is an optimal computation
+ point. */
+static sbitmap *pre_optimal;
+
+/* Nonzero for expressions which are redundant in a particular block. */
+static sbitmap *pre_redundant;
+
+/* Nonzero for expressions which should be inserted on a specific edge. */
+static sbitmap *pre_insert_map;
+
+/* Nonzero for expressions which should be deleted in a specific block. */
+static sbitmap *pre_delete_map;
+
+/* Contains the edge_list returned by pre_edge_lcm. */
+static struct edge_list *edge_list;
+
+/* Allocate vars used for PRE analysis. */
+
+static void
+alloc_pre_mem (int n_blocks, int n_exprs)
+{
+ transp = sbitmap_vector_alloc (n_blocks, n_exprs);
+ comp = sbitmap_vector_alloc (n_blocks, n_exprs);
+ antloc = sbitmap_vector_alloc (n_blocks, n_exprs);
+
+ pre_optimal = NULL;
+ pre_redundant = NULL;
+ pre_insert_map = NULL;
+ pre_delete_map = NULL;
+ ae_kill = sbitmap_vector_alloc (n_blocks, n_exprs);
+
+ /* pre_insert and pre_delete are allocated later. */
+}
+
+/* Free vars used for PRE analysis. */
+
+static void
+free_pre_mem (void)
+{
+ sbitmap_vector_free (transp);
+ sbitmap_vector_free (comp);
+
+ /* ANTLOC and AE_KILL are freed just after pre_lcm finishes. */
+
+ if (pre_optimal)
+ sbitmap_vector_free (pre_optimal);
+ if (pre_redundant)
+ sbitmap_vector_free (pre_redundant);
+ if (pre_insert_map)
+ sbitmap_vector_free (pre_insert_map);
+ if (pre_delete_map)
+ sbitmap_vector_free (pre_delete_map);
+
+ transp = comp = NULL;
+ pre_optimal = pre_redundant = pre_insert_map = pre_delete_map = NULL;
+}
+
+/* Remove certain expressions from anticipatable and transparent
+ sets of basic blocks that have incoming abnormal edge.
+ For PRE remove potentially trapping expressions to avoid placing
+ them on abnormal edges. For hoisting remove memory references that
+ can be clobbered by calls. */
+
+static void
+prune_expressions (bool pre_p)
+{
+ sbitmap prune_exprs;
+ unsigned int ui;
+ basic_block bb;
+
+ prune_exprs = sbitmap_alloc (expr_hash_table.n_elems);
+ sbitmap_zero (prune_exprs);
+ for (ui = 0; ui < expr_hash_table.size; ui++)
+ {
+ struct expr *e;
+ for (e = expr_hash_table.table[ui]; e != NULL; e = e->next_same_hash)
+ {
+ /* Note potentially trapping expressions. */
+ if (may_trap_p (e->expr))
+ {
+ SET_BIT (prune_exprs, e->bitmap_index);
+ continue;
+ }
+
+ if (!pre_p && MEM_P (e->expr))
+ /* Note memory references that can be clobbered by a call.
+ We do not split abnormal edges in hoisting, so would
+ a memory reference get hoisted along an abnormal edge,
+ it would be placed /before/ the call. Therefore, only
+ constant memory references can be hoisted along abnormal
+ edges. */
+ {
+ if (GET_CODE (XEXP (e->expr, 0)) == SYMBOL_REF
+ && CONSTANT_POOL_ADDRESS_P (XEXP (e->expr, 0)))
+ continue;
+
+ if (MEM_READONLY_P (e->expr)
+ && !MEM_VOLATILE_P (e->expr)
+ && MEM_NOTRAP_P (e->expr))
+ /* Constant memory reference, e.g., a PIC address. */
+ continue;
+
+ /* ??? Optimally, we would use interprocedural alias
+ analysis to determine if this mem is actually killed
+ by this call. */
+
+ SET_BIT (prune_exprs, e->bitmap_index);
+ }
+ }
+ }
+
+ FOR_EACH_BB (bb)
+ {
+ edge e;
+ edge_iterator ei;
+
+ /* If the current block is the destination of an abnormal edge, we
+ kill all trapping (for PRE) and memory (for hoist) expressions
+ because we won't be able to properly place the instruction on
+ the edge. So make them neither anticipatable nor transparent.
+ This is fairly conservative.
+
+ ??? For hoisting it may be necessary to check for set-and-jump
+ instructions here, not just for abnormal edges. The general problem
+ is that when an expression cannot not be placed right at the end of
+ a basic block we should account for any side-effects of a subsequent
+ jump instructions that could clobber the expression. It would
+ be best to implement this check along the lines of
+ hoist_expr_reaches_here_p where the target block is already known
+ and, hence, there's no need to conservatively prune expressions on
+ "intermediate" set-and-jump instructions. */
+ FOR_EACH_EDGE (e, ei, bb->preds)
+ if ((e->flags & EDGE_ABNORMAL)
+ && (pre_p || CALL_P (BB_END (e->src))))
+ {
+ sbitmap_difference (antloc[bb->index],
+ antloc[bb->index], prune_exprs);
+ sbitmap_difference (transp[bb->index],
+ transp[bb->index], prune_exprs);
+ break;
+ }
+ }
+
+ sbitmap_free (prune_exprs);
+}
+
+/* It may be necessary to insert a large number of insns on edges to
+ make the existing occurrences of expressions fully redundant. This
+ routine examines the set of insertions and deletions and if the ratio
+ of insertions to deletions is too high for a particular expression, then
+ the expression is removed from the insertion/deletion sets.
+
+ N_ELEMS is the number of elements in the hash table. */
+
+static void
+prune_insertions_deletions (int n_elems)
+{
+ sbitmap_iterator sbi;
+ sbitmap prune_exprs;
+
+ /* We always use I to iterate over blocks/edges and J to iterate over
+ expressions. */
+ unsigned int i, j;
+
+ /* Counts for the number of times an expression needs to be inserted and
+ number of times an expression can be removed as a result. */
+ int *insertions = GCNEWVEC (int, n_elems);
+ int *deletions = GCNEWVEC (int, n_elems);
+
+ /* Set of expressions which require too many insertions relative to
+ the number of deletions achieved. We will prune these out of the
+ insertion/deletion sets. */
+ prune_exprs = sbitmap_alloc (n_elems);
+ sbitmap_zero (prune_exprs);
+
+ /* Iterate over the edges counting the number of times each expression
+ needs to be inserted. */
+ for (i = 0; i < (unsigned) n_edges; i++)
+ {
+ EXECUTE_IF_SET_IN_SBITMAP (pre_insert_map[i], 0, j, sbi)
+ insertions[j]++;
+ }
+
+ /* Similarly for deletions, but those occur in blocks rather than on
+ edges. */
+ for (i = 0; i < (unsigned) last_basic_block; i++)
+ {
+ EXECUTE_IF_SET_IN_SBITMAP (pre_delete_map[i], 0, j, sbi)
+ deletions[j]++;
+ }
+
+ /* Now that we have accurate counts, iterate over the elements in the
+ hash table and see if any need too many insertions relative to the
+ number of evaluations that can be removed. If so, mark them in
+ PRUNE_EXPRS. */
+ for (j = 0; j < (unsigned) n_elems; j++)
+ if (deletions[j]
+ && ((unsigned) insertions[j] / deletions[j]) > MAX_GCSE_INSERTION_RATIO)
+ SET_BIT (prune_exprs, j);
+
+ /* Now prune PRE_INSERT_MAP and PRE_DELETE_MAP based on PRUNE_EXPRS. */
+ EXECUTE_IF_SET_IN_SBITMAP (prune_exprs, 0, j, sbi)
+ {
+ for (i = 0; i < (unsigned) n_edges; i++)
+ RESET_BIT (pre_insert_map[i], j);
+
+ for (i = 0; i < (unsigned) last_basic_block; i++)
+ RESET_BIT (pre_delete_map[i], j);
+ }
+
+ sbitmap_free (prune_exprs);
+ free (insertions);
+ free (deletions);
+}
+
+/* Top level routine to do the dataflow analysis needed by PRE. */
+
+static void
+compute_pre_data (void)
+{
+ basic_block bb;
+
+ compute_local_properties (transp, comp, antloc, &expr_hash_table);
+ prune_expressions (true);
+ sbitmap_vector_zero (ae_kill, last_basic_block);
+
+ /* Compute ae_kill for each basic block using:
+
+ ~(TRANSP | COMP)
+ */
+
+ FOR_EACH_BB (bb)
+ {
+ sbitmap_a_or_b (ae_kill[bb->index], transp[bb->index], comp[bb->index]);
+ sbitmap_not (ae_kill[bb->index], ae_kill[bb->index]);
+ }
+
+ edge_list = pre_edge_lcm (expr_hash_table.n_elems, transp, comp, antloc,
+ ae_kill, &pre_insert_map, &pre_delete_map);
+ sbitmap_vector_free (antloc);
+ antloc = NULL;
+ sbitmap_vector_free (ae_kill);
+ ae_kill = NULL;
+
+ prune_insertions_deletions (expr_hash_table.n_elems);
+}
+
+/* PRE utilities */
+
+/* Return nonzero if an occurrence of expression EXPR in OCCR_BB would reach
+ block BB.
+
+ VISITED is a pointer to a working buffer for tracking which BB's have
+ been visited. It is NULL for the top-level call.
+
+ We treat reaching expressions that go through blocks containing the same
+ reaching expression as "not reaching". E.g. if EXPR is generated in blocks
+ 2 and 3, INSN is in block 4, and 2->3->4, we treat the expression in block
+ 2 as not reaching. The intent is to improve the probability of finding
+ only one reaching expression and to reduce register lifetimes by picking
+ the closest such expression. */
+
+static int
+pre_expr_reaches_here_p_work (basic_block occr_bb, struct expr *expr, basic_block bb, char *visited)
+{
+ edge pred;
+ edge_iterator ei;
+
+ FOR_EACH_EDGE (pred, ei, bb->preds)
+ {
+ basic_block pred_bb = pred->src;
+
+ if (pred->src == ENTRY_BLOCK_PTR
+ /* Has predecessor has already been visited? */
+ || visited[pred_bb->index])
+ ;/* Nothing to do. */
+
+ /* Does this predecessor generate this expression? */
+ else if (TEST_BIT (comp[pred_bb->index], expr->bitmap_index))
+ {
+ /* Is this the occurrence we're looking for?
+ Note that there's only one generating occurrence per block
+ so we just need to check the block number. */
+ if (occr_bb == pred_bb)
+ return 1;
+
+ visited[pred_bb->index] = 1;
+ }
+ /* Ignore this predecessor if it kills the expression. */
+ else if (! TEST_BIT (transp[pred_bb->index], expr->bitmap_index))
+ visited[pred_bb->index] = 1;
+
+ /* Neither gen nor kill. */
+ else
+ {
+ visited[pred_bb->index] = 1;
+ if (pre_expr_reaches_here_p_work (occr_bb, expr, pred_bb, visited))
+ return 1;
+ }
+ }
+
+ /* All paths have been checked. */
+ return 0;
+}
+
+/* The wrapper for pre_expr_reaches_here_work that ensures that any
+ memory allocated for that function is returned. */
+
+static int
+pre_expr_reaches_here_p (basic_block occr_bb, struct expr *expr, basic_block bb)
+{
+ int rval;
+ char *visited = XCNEWVEC (char, last_basic_block);
+
+ rval = pre_expr_reaches_here_p_work (occr_bb, expr, bb, visited);
+
+ free (visited);
+ return rval;
+}
+
+
+/* Given an expr, generate RTL which we can insert at the end of a BB,
+ or on an edge. Set the block number of any insns generated to
+ the value of BB. */
+
+static rtx
+process_insert_insn (struct expr *expr)
+{
+ rtx reg = expr->reaching_reg;
+ rtx exp = copy_rtx (expr->expr);
+ rtx pat;
+
+ start_sequence ();
+
+ /* If the expression is something that's an operand, like a constant,
+ just copy it to a register. */
+ if (general_operand (exp, GET_MODE (reg)))
+ emit_move_insn (reg, exp);
+
+ /* Otherwise, make a new insn to compute this expression and make sure the
+ insn will be recognized (this also adds any needed CLOBBERs). Copy the
+ expression to make sure we don't have any sharing issues. */
+ else
+ {
+ rtx insn = emit_insn (gen_rtx_SET (VOIDmode, reg, exp));
+
+ if (insn_invalid_p (insn))
+ gcc_unreachable ();
+ }
+
+
+ pat = get_insns ();
+ end_sequence ();
+
+ return pat;
+}
+
+/* Add EXPR to the end of basic block BB.
+
+ This is used by both the PRE and code hoisting. */
+
+static void
+insert_insn_end_basic_block (struct expr *expr, basic_block bb)
+{
+ rtx insn = BB_END (bb);
+ rtx new_insn;
+ rtx reg = expr->reaching_reg;
+ int regno = REGNO (reg);
+ rtx pat, pat_end;
+
+ pat = process_insert_insn (expr);
+ gcc_assert (pat && INSN_P (pat));
+
+ pat_end = pat;
+ while (NEXT_INSN (pat_end) != NULL_RTX)
+ pat_end = NEXT_INSN (pat_end);
+
+ /* If the last insn is a jump, insert EXPR in front [taking care to
+ handle cc0, etc. properly]. Similarly we need to care trapping
+ instructions in presence of non-call exceptions. */
+
+ if (JUMP_P (insn)
+ || (NONJUMP_INSN_P (insn)
+ && (!single_succ_p (bb)
+ || single_succ_edge (bb)->flags & EDGE_ABNORMAL)))
+ {
+#ifdef HAVE_cc0
+ rtx note;
+#endif
+
+ /* If this is a jump table, then we can't insert stuff here. Since
+ we know the previous real insn must be the tablejump, we insert
+ the new instruction just before the tablejump. */
+ if (GET_CODE (PATTERN (insn)) == ADDR_VEC
+ || GET_CODE (PATTERN (insn)) == ADDR_DIFF_VEC)
+ insn = prev_active_insn (insn);
+
+#ifdef HAVE_cc0
+ /* FIXME: 'twould be nice to call prev_cc0_setter here but it aborts
+ if cc0 isn't set. */
+ note = find_reg_note (insn, REG_CC_SETTER, NULL_RTX);
+ if (note)
+ insn = XEXP (note, 0);
+ else
+ {
+ rtx maybe_cc0_setter = prev_nonnote_insn (insn);
+ if (maybe_cc0_setter
+ && INSN_P (maybe_cc0_setter)
+ && sets_cc0_p (PATTERN (maybe_cc0_setter)))
+ insn = maybe_cc0_setter;
+ }
+#endif
+ /* FIXME: What if something in cc0/jump uses value set in new insn? */
+ new_insn = emit_insn_before_noloc (pat, insn, bb);
+ }
+
+ /* Likewise if the last insn is a call, as will happen in the presence
+ of exception handling. */
+ else if (CALL_P (insn)
+ && (!single_succ_p (bb)
+ || single_succ_edge (bb)->flags & EDGE_ABNORMAL))
+ {
+ /* Keeping in mind targets with small register classes and parameters
+ in registers, we search backward and place the instructions before
+ the first parameter is loaded. Do this for everyone for consistency
+ and a presumption that we'll get better code elsewhere as well. */
+
+ /* Since different machines initialize their parameter registers
+ in different orders, assume nothing. Collect the set of all
+ parameter registers. */
+ insn = find_first_parameter_load (insn, BB_HEAD (bb));
+
+ /* If we found all the parameter loads, then we want to insert
+ before the first parameter load.
+
+ If we did not find all the parameter loads, then we might have
+ stopped on the head of the block, which could be a CODE_LABEL.
+ If we inserted before the CODE_LABEL, then we would be putting
+ the insn in the wrong basic block. In that case, put the insn
+ after the CODE_LABEL. Also, respect NOTE_INSN_BASIC_BLOCK. */
+ while (LABEL_P (insn)
+ || NOTE_INSN_BASIC_BLOCK_P (insn))
+ insn = NEXT_INSN (insn);
+
+ new_insn = emit_insn_before_noloc (pat, insn, bb);
+ }
+ else
+ new_insn = emit_insn_after_noloc (pat, insn, bb);
+
+ while (1)
+ {
+ if (INSN_P (pat))
+ add_label_notes (PATTERN (pat), new_insn);
+ if (pat == pat_end)
+ break;
+ pat = NEXT_INSN (pat);
+ }
+
+ gcse_create_count++;
+
+ if (dump_file)
+ {
+ fprintf (dump_file, "PRE/HOIST: end of bb %d, insn %d, ",
+ bb->index, INSN_UID (new_insn));
+ fprintf (dump_file, "copying expression %d to reg %d\n",
+ expr->bitmap_index, regno);
+ }
+}
+
+/* Insert partially redundant expressions on edges in the CFG to make
+ the expressions fully redundant. */
+
+static int
+pre_edge_insert (struct edge_list *edge_list, struct expr **index_map)
+{
+ int e, i, j, num_edges, set_size, did_insert = 0;
+ sbitmap *inserted;
+
+ /* Where PRE_INSERT_MAP is nonzero, we add the expression on that edge
+ if it reaches any of the deleted expressions. */
+
+ set_size = pre_insert_map[0]->size;
+ num_edges = NUM_EDGES (edge_list);
+ inserted = sbitmap_vector_alloc (num_edges, expr_hash_table.n_elems);
+ sbitmap_vector_zero (inserted, num_edges);
+
+ for (e = 0; e < num_edges; e++)
+ {
+ int indx;
+ basic_block bb = INDEX_EDGE_PRED_BB (edge_list, e);
+
+ for (i = indx = 0; i < set_size; i++, indx += SBITMAP_ELT_BITS)
+ {
+ SBITMAP_ELT_TYPE insert = pre_insert_map[e]->elms[i];
+
+ for (j = indx; insert && j < (int) expr_hash_table.n_elems; j++, insert >>= 1)
+ if ((insert & 1) != 0 && index_map[j]->reaching_reg != NULL_RTX)
+ {
+ struct expr *expr = index_map[j];
+ struct occr *occr;
+
+ /* Now look at each deleted occurrence of this expression. */
+ for (occr = expr->antic_occr; occr != NULL; occr = occr->next)
+ {
+ if (! occr->deleted_p)
+ continue;
+
+ /* Insert this expression on this edge if it would
+ reach the deleted occurrence in BB. */
+ if (!TEST_BIT (inserted[e], j))
+ {
+ rtx insn;
+ edge eg = INDEX_EDGE (edge_list, e);
+
+ /* We can't insert anything on an abnormal and
+ critical edge, so we insert the insn at the end of
+ the previous block. There are several alternatives
+ detailed in Morgans book P277 (sec 10.5) for
+ handling this situation. This one is easiest for
+ now. */
+
+ if (eg->flags & EDGE_ABNORMAL)
+ insert_insn_end_basic_block (index_map[j], bb);
+ else
+ {
+ insn = process_insert_insn (index_map[j]);
+ insert_insn_on_edge (insn, eg);
+ }
+
+ if (dump_file)
+ {
+ fprintf (dump_file, "PRE: edge (%d,%d), ",
+ bb->index,
+ INDEX_EDGE_SUCC_BB (edge_list, e)->index);
+ fprintf (dump_file, "copy expression %d\n",
+ expr->bitmap_index);
+ }
+
+ update_ld_motion_stores (expr);
+ SET_BIT (inserted[e], j);
+ did_insert = 1;
+ gcse_create_count++;
+ }
+ }
+ }
+ }
+ }
+
+ sbitmap_vector_free (inserted);
+ return did_insert;
+}
+
+/* Copy the result of EXPR->EXPR generated by INSN to EXPR->REACHING_REG.
+ Given "old_reg <- expr" (INSN), instead of adding after it
+ reaching_reg <- old_reg
+ it's better to do the following:
+ reaching_reg <- expr
+ old_reg <- reaching_reg
+ because this way copy propagation can discover additional PRE
+ opportunities. But if this fails, we try the old way.
+ When "expr" is a store, i.e.
+ given "MEM <- old_reg", instead of adding after it
+ reaching_reg <- old_reg
+ it's better to add it before as follows:
+ reaching_reg <- old_reg
+ MEM <- reaching_reg. */
+
+static void
+pre_insert_copy_insn (struct expr *expr, rtx insn)
+{
+ rtx reg = expr->reaching_reg;
+ int regno = REGNO (reg);
+ int indx = expr->bitmap_index;
+ rtx pat = PATTERN (insn);
+ rtx set, first_set, new_insn;
+ rtx old_reg;
+ int i;
+
+ /* This block matches the logic in hash_scan_insn. */
+ switch (GET_CODE (pat))
+ {
+ case SET:
+ set = pat;
+ break;
+
+ case PARALLEL:
+ /* Search through the parallel looking for the set whose
+ source was the expression that we're interested in. */
+ first_set = NULL_RTX;
+ set = NULL_RTX;
+ for (i = 0; i < XVECLEN (pat, 0); i++)
+ {
+ rtx x = XVECEXP (pat, 0, i);
+ if (GET_CODE (x) == SET)
+ {
+ /* If the source was a REG_EQUAL or REG_EQUIV note, we
+ may not find an equivalent expression, but in this
+ case the PARALLEL will have a single set. */
+ if (first_set == NULL_RTX)
+ first_set = x;
+ if (expr_equiv_p (SET_SRC (x), expr->expr))
+ {
+ set = x;
+ break;
+ }
+ }
+ }
+
+ gcc_assert (first_set);
+ if (set == NULL_RTX)
+ set = first_set;
+ break;
+
+ default:
+ gcc_unreachable ();
+ }
+
+ if (REG_P (SET_DEST (set)))
+ {
+ old_reg = SET_DEST (set);
+ /* Check if we can modify the set destination in the original insn. */
+ if (validate_change (insn, &SET_DEST (set), reg, 0))
+ {
+ new_insn = gen_move_insn (old_reg, reg);
+ new_insn = emit_insn_after (new_insn, insn);
+ }
+ else
+ {
+ new_insn = gen_move_insn (reg, old_reg);
+ new_insn = emit_insn_after (new_insn, insn);
+ }
+ }
+ else /* This is possible only in case of a store to memory. */
+ {
+ old_reg = SET_SRC (set);
+ new_insn = gen_move_insn (reg, old_reg);
+
+ /* Check if we can modify the set source in the original insn. */
+ if (validate_change (insn, &SET_SRC (set), reg, 0))
+ new_insn = emit_insn_before (new_insn, insn);
+ else
+ new_insn = emit_insn_after (new_insn, insn);
+ }
+
+ gcse_create_count++;
+
+ if (dump_file)
+ fprintf (dump_file,
+ "PRE: bb %d, insn %d, copy expression %d in insn %d to reg %d\n",
+ BLOCK_FOR_INSN (insn)->index, INSN_UID (new_insn), indx,
+ INSN_UID (insn), regno);
+}
+
+/* Copy available expressions that reach the redundant expression
+ to `reaching_reg'. */
+
+static void
+pre_insert_copies (void)
+{
+ unsigned int i, added_copy;
+ struct expr *expr;
+ struct occr *occr;
+ struct occr *avail;
+
+ /* For each available expression in the table, copy the result to
+ `reaching_reg' if the expression reaches a deleted one.
+
+ ??? The current algorithm is rather brute force.
+ Need to do some profiling. */
+
+ for (i = 0; i < expr_hash_table.size; i++)
+ for (expr = expr_hash_table.table[i]; expr != NULL; expr = expr->next_same_hash)
+ {
+ /* If the basic block isn't reachable, PPOUT will be TRUE. However,
+ we don't want to insert a copy here because the expression may not
+ really be redundant. So only insert an insn if the expression was
+ deleted. This test also avoids further processing if the
+ expression wasn't deleted anywhere. */
+ if (expr->reaching_reg == NULL)
+ continue;
+
+ /* Set when we add a copy for that expression. */
+ added_copy = 0;
+
+ for (occr = expr->antic_occr; occr != NULL; occr = occr->next)
+ {
+ if (! occr->deleted_p)
+ continue;
+
+ for (avail = expr->avail_occr; avail != NULL; avail = avail->next)
+ {
+ rtx insn = avail->insn;
+
+ /* No need to handle this one if handled already. */
+ if (avail->copied_p)
+ continue;
+
+ /* Don't handle this one if it's a redundant one. */
+ if (INSN_DELETED_P (insn))
+ continue;
+
+ /* Or if the expression doesn't reach the deleted one. */
+ if (! pre_expr_reaches_here_p (BLOCK_FOR_INSN (avail->insn),
+ expr,
+ BLOCK_FOR_INSN (occr->insn)))
+ continue;
+
+ added_copy = 1;
+
+ /* Copy the result of avail to reaching_reg. */
+ pre_insert_copy_insn (expr, insn);
+ avail->copied_p = 1;
+ }
+ }
+
+ if (added_copy)
+ update_ld_motion_stores (expr);
+ }
+}
+
+/* Emit move from SRC to DEST noting the equivalence with expression computed
+ in INSN. */
+static rtx
+gcse_emit_move_after (rtx src, rtx dest, rtx insn)
+{
+ rtx new_rtx;
+ rtx set = single_set (insn), set2;
+ rtx note;
+ rtx eqv;
+
+ /* This should never fail since we're creating a reg->reg copy
+ we've verified to be valid. */
+
+ new_rtx = emit_insn_after (gen_move_insn (dest, src), insn);
+
+ /* Note the equivalence for local CSE pass. */
+ set2 = single_set (new_rtx);
+ if (!set2 || !rtx_equal_p (SET_DEST (set2), dest))
+ return new_rtx;
+ if ((note = find_reg_equal_equiv_note (insn)))
+ eqv = XEXP (note, 0);
+ else
+ eqv = SET_SRC (set);
+
+ set_unique_reg_note (new_rtx, REG_EQUAL, copy_insn_1 (eqv));
+
+ return new_rtx;
+}
+
+/* Delete redundant computations.
+ Deletion is done by changing the insn to copy the `reaching_reg' of
+ the expression into the result of the SET. It is left to later passes
+ (cprop, cse2, flow, combine, regmove) to propagate the copy or eliminate it.
+
+ Returns nonzero if a change is made. */
+
+static int
+pre_delete (void)
+{
+ unsigned int i;
+ int changed;
+ struct expr *expr;
+ struct occr *occr;
+
+ changed = 0;
+ for (i = 0; i < expr_hash_table.size; i++)
+ for (expr = expr_hash_table.table[i];
+ expr != NULL;
+ expr = expr->next_same_hash)
+ {
+ int indx = expr->bitmap_index;
+
+ /* We only need to search antic_occr since we require
+ ANTLOC != 0. */
+
+ for (occr = expr->antic_occr; occr != NULL; occr = occr->next)
+ {
+ rtx insn = occr->insn;
+ rtx set;
+ basic_block bb = BLOCK_FOR_INSN (insn);
+
+ /* We only delete insns that have a single_set. */
+ if (TEST_BIT (pre_delete_map[bb->index], indx)
+ && (set = single_set (insn)) != 0
+ && dbg_cnt (pre_insn))
+ {
+ /* Create a pseudo-reg to store the result of reaching
+ expressions into. Get the mode for the new pseudo from
+ the mode of the original destination pseudo. */
+ if (expr->reaching_reg == NULL)
+ expr->reaching_reg = gen_reg_rtx_and_attrs (SET_DEST (set));
+
+ gcse_emit_move_after (expr->reaching_reg, SET_DEST (set), insn);
+ delete_insn (insn);
+ occr->deleted_p = 1;
+ changed = 1;
+ gcse_subst_count++;
+
+ if (dump_file)
+ {
+ fprintf (dump_file,
+ "PRE: redundant insn %d (expression %d) in ",
+ INSN_UID (insn), indx);
+ fprintf (dump_file, "bb %d, reaching reg is %d\n",
+ bb->index, REGNO (expr->reaching_reg));
+ }
+ }
+ }
+ }
+
+ return changed;
+}
+
+/* Perform GCSE optimizations using PRE.
+ This is called by one_pre_gcse_pass after all the dataflow analysis
+ has been done.
+
+ This is based on the original Morel-Renvoise paper Fred Chow's thesis, and
+ lazy code motion from Knoop, Ruthing and Steffen as described in Advanced
+ Compiler Design and Implementation.
+
+ ??? A new pseudo reg is created to hold the reaching expression. The nice
+ thing about the classical approach is that it would try to use an existing
+ reg. If the register can't be adequately optimized [i.e. we introduce
+ reload problems], one could add a pass here to propagate the new register
+ through the block.
+
+ ??? We don't handle single sets in PARALLELs because we're [currently] not
+ able to copy the rest of the parallel when we insert copies to create full
+ redundancies from partial redundancies. However, there's no reason why we
+ can't handle PARALLELs in the cases where there are no partial
+ redundancies. */
+
+static int
+pre_gcse (void)
+{
+ unsigned int i;
+ int did_insert, changed;
+ struct expr **index_map;
+ struct expr *expr;
+
+ /* Compute a mapping from expression number (`bitmap_index') to
+ hash table entry. */
+
+ index_map = XCNEWVEC (struct expr *, expr_hash_table.n_elems);
+ for (i = 0; i < expr_hash_table.size; i++)
+ for (expr = expr_hash_table.table[i]; expr != NULL; expr = expr->next_same_hash)
+ index_map[expr->bitmap_index] = expr;
+
+ /* Delete the redundant insns first so that
+ - we know what register to use for the new insns and for the other
+ ones with reaching expressions
+ - we know which insns are redundant when we go to create copies */
+
+ changed = pre_delete ();
+ did_insert = pre_edge_insert (edge_list, index_map);
+
+ /* In other places with reaching expressions, copy the expression to the
+ specially allocated pseudo-reg that reaches the redundant expr. */
+ pre_insert_copies ();
+ if (did_insert)
+ {
+ commit_edge_insertions ();
+ changed = 1;
+ }
+
+ free (index_map);
+ return changed;
+}
+
+/* Top level routine to perform one PRE GCSE pass.
+
+ Return nonzero if a change was made. */
+
+static int
+one_pre_gcse_pass (void)
+{
+ int changed = 0;
+
+ gcse_subst_count = 0;
+ gcse_create_count = 0;
+
+ /* Return if there's nothing to do, or it is too expensive. */
+ if (n_basic_blocks <= NUM_FIXED_BLOCKS + 1
+ || is_too_expensive (_("PRE disabled")))
+ return 0;
+
+ /* We need alias. */
+ init_alias_analysis ();
+
+ bytes_used = 0;
+ gcc_obstack_init (&gcse_obstack);
+ alloc_gcse_mem ();
+
+ alloc_hash_table (&expr_hash_table, 0);
+ add_noreturn_fake_exit_edges ();
+ if (flag_gcse_lm)
+ compute_ld_motion_mems ();
+
+ compute_hash_table (&expr_hash_table);
+ trim_ld_motion_mems ();
+ if (dump_file)
+ dump_hash_table (dump_file, "Expression", &expr_hash_table);
+
+ if (expr_hash_table.n_elems > 0)
+ {
+ alloc_pre_mem (last_basic_block, expr_hash_table.n_elems);
+ compute_pre_data ();
+ changed |= pre_gcse ();
+ free_edge_list (edge_list);
+ free_pre_mem ();
+ }
+
+ free_ldst_mems ();
+ remove_fake_exit_edges ();
+ free_hash_table (&expr_hash_table);
+
+ free_gcse_mem ();
+ obstack_free (&gcse_obstack, NULL);
+
+ /* We are finished with alias. */
+ end_alias_analysis ();
+
+ if (dump_file)
+ {
+ fprintf (dump_file, "PRE GCSE of %s, %d basic blocks, %d bytes needed, ",
+ current_function_name (), n_basic_blocks, bytes_used);
+ fprintf (dump_file, "%d substs, %d insns created\n",
+ gcse_subst_count, gcse_create_count);
+ }
+
+ return changed;
+}
+
+/* If X contains any LABEL_REF's, add REG_LABEL_OPERAND notes for them
+ to INSN. If such notes are added to an insn which references a
+ CODE_LABEL, the LABEL_NUSES count is incremented. We have to add
+ that note, because the following loop optimization pass requires
+ them. */
+
+/* ??? If there was a jump optimization pass after gcse and before loop,
+ then we would not need to do this here, because jump would add the
+ necessary REG_LABEL_OPERAND and REG_LABEL_TARGET notes. */
+
+static void
+add_label_notes (rtx x, rtx insn)
+{
+ enum rtx_code code = GET_CODE (x);
+ int i, j;
+ const char *fmt;
+
+ if (code == LABEL_REF && !LABEL_REF_NONLOCAL_P (x))
+ {
+ /* This code used to ignore labels that referred to dispatch tables to
+ avoid flow generating (slightly) worse code.
+
+ We no longer ignore such label references (see LABEL_REF handling in
+ mark_jump_label for additional information). */
+
+ /* There's no reason for current users to emit jump-insns with
+ such a LABEL_REF, so we don't have to handle REG_LABEL_TARGET
+ notes. */
+ gcc_assert (!JUMP_P (insn));
+ add_reg_note (insn, REG_LABEL_OPERAND, XEXP (x, 0));
+
+ if (LABEL_P (XEXP (x, 0)))
+ LABEL_NUSES (XEXP (x, 0))++;
+
+ return;
+ }
+
+ for (i = GET_RTX_LENGTH (code) - 1, fmt = GET_RTX_FORMAT (code); i >= 0; i--)
+ {
+ if (fmt[i] == 'e')
+ add_label_notes (XEXP (x, i), insn);
+ else if (fmt[i] == 'E')
+ for (j = XVECLEN (x, i) - 1; j >= 0; j--)
+ add_label_notes (XVECEXP (x, i, j), insn);
+ }
+}
+
+/* Code Hoisting variables and subroutines. */
+
+/* Very busy expressions. */
+static sbitmap *hoist_vbein;
+static sbitmap *hoist_vbeout;
+
+/* ??? We could compute post dominators and run this algorithm in
+ reverse to perform tail merging, doing so would probably be
+ more effective than the tail merging code in jump.c.
+
+ It's unclear if tail merging could be run in parallel with
+ code hoisting. It would be nice. */
+
+/* Allocate vars used for code hoisting analysis. */
+
+static void
+alloc_code_hoist_mem (int n_blocks, int n_exprs)
+{
+ antloc = sbitmap_vector_alloc (n_blocks, n_exprs);
+ transp = sbitmap_vector_alloc (n_blocks, n_exprs);
+ comp = sbitmap_vector_alloc (n_blocks, n_exprs);
+
+ hoist_vbein = sbitmap_vector_alloc (n_blocks, n_exprs);
+ hoist_vbeout = sbitmap_vector_alloc (n_blocks, n_exprs);
+}
+
+/* Free vars used for code hoisting analysis. */
+
+static void
+free_code_hoist_mem (void)
+{
+ sbitmap_vector_free (antloc);
+ sbitmap_vector_free (transp);
+ sbitmap_vector_free (comp);
+
+ sbitmap_vector_free (hoist_vbein);
+ sbitmap_vector_free (hoist_vbeout);
+
+ free_dominance_info (CDI_DOMINATORS);
+}
+
+/* Compute the very busy expressions at entry/exit from each block.
+
+ An expression is very busy if all paths from a given point
+ compute the expression. */
+
+static void
+compute_code_hoist_vbeinout (void)
+{
+ int changed, passes;
+ basic_block bb;
+
+ sbitmap_vector_zero (hoist_vbeout, last_basic_block);
+ sbitmap_vector_zero (hoist_vbein, last_basic_block);
+
+ passes = 0;
+ changed = 1;
+
+ while (changed)
+ {
+ changed = 0;
+
+ /* We scan the blocks in the reverse order to speed up
+ the convergence. */
+ FOR_EACH_BB_REVERSE (bb)
+ {
+ if (bb->next_bb != EXIT_BLOCK_PTR)
+ {
+ sbitmap_intersection_of_succs (hoist_vbeout[bb->index],
+ hoist_vbein, bb->index);
+
+ /* Include expressions in VBEout that are calculated
+ in BB and available at its end. */
+ sbitmap_a_or_b (hoist_vbeout[bb->index],
+ hoist_vbeout[bb->index], comp[bb->index]);
+ }
+
+ changed |= sbitmap_a_or_b_and_c_cg (hoist_vbein[bb->index],
+ antloc[bb->index],
+ hoist_vbeout[bb->index],
+ transp[bb->index]);
+ }
+
+ passes++;
+ }
+
+ if (dump_file)
+ {
+ fprintf (dump_file, "hoisting vbeinout computation: %d passes\n", passes);
+
+ FOR_EACH_BB (bb)
+ {
+ fprintf (dump_file, "vbein (%d): ", bb->index);
+ dump_sbitmap_file (dump_file, hoist_vbein[bb->index]);
+ fprintf (dump_file, "vbeout(%d): ", bb->index);
+ dump_sbitmap_file (dump_file, hoist_vbeout[bb->index]);
+ }
+ }
+}
+
+/* Top level routine to do the dataflow analysis needed by code hoisting. */
+
+static void
+compute_code_hoist_data (void)
+{
+ compute_local_properties (transp, comp, antloc, &expr_hash_table);
+ prune_expressions (false);
+ compute_code_hoist_vbeinout ();
+ calculate_dominance_info (CDI_DOMINATORS);
+ if (dump_file)
+ fprintf (dump_file, "\n");
+}
+
+/* Determine if the expression identified by EXPR_INDEX would
+ reach BB unimpared if it was placed at the end of EXPR_BB.
+ Stop the search if the expression would need to be moved more
+ than DISTANCE instructions.
+
+ It's unclear exactly what Muchnick meant by "unimpared". It seems
+ to me that the expression must either be computed or transparent in
+ *every* block in the path(s) from EXPR_BB to BB. Any other definition
+ would allow the expression to be hoisted out of loops, even if
+ the expression wasn't a loop invariant.
+
+ Contrast this to reachability for PRE where an expression is
+ considered reachable if *any* path reaches instead of *all*
+ paths. */
+
+static int
+hoist_expr_reaches_here_p (basic_block expr_bb, int expr_index, basic_block bb,
+ char *visited, int distance, int *bb_size)
+{
+ edge pred;
+ edge_iterator ei;
+ int visited_allocated_locally = 0;
+
+ /* Terminate the search if distance, for which EXPR is allowed to move,
+ is exhausted. */
+ if (distance > 0)
+ {
+ distance -= bb_size[bb->index];
+
+ if (distance <= 0)
+ return 0;
+ }
+ else
+ gcc_assert (distance == 0);
+
+ if (visited == NULL)
+ {
+ visited_allocated_locally = 1;
+ visited = XCNEWVEC (char, last_basic_block);
+ }
+
+ FOR_EACH_EDGE (pred, ei, bb->preds)
+ {
+ basic_block pred_bb = pred->src;
+
+ if (pred->src == ENTRY_BLOCK_PTR)
+ break;
+ else if (pred_bb == expr_bb)
+ continue;
+ else if (visited[pred_bb->index])
+ continue;
+
+ else if (! TEST_BIT (transp[pred_bb->index], expr_index))
+ break;
+
+ /* Not killed. */
+ else
+ {
+ visited[pred_bb->index] = 1;
+ if (! hoist_expr_reaches_here_p (expr_bb, expr_index, pred_bb,
+ visited, distance, bb_size))
+ break;
+ }
+ }
+ if (visited_allocated_locally)
+ free (visited);
+
+ return (pred == NULL);
+}
+
+/* Find occurence in BB. */
+static struct occr *
+find_occr_in_bb (struct occr *occr, basic_block bb)
+{
+ /* Find the right occurrence of this expression. */
+ while (occr && BLOCK_FOR_INSN (occr->insn) != bb)
+ occr = occr->next;
+
+ return occr;
+}
+
+/* Actually perform code hoisting. */
+
+static int
+hoist_code (void)
+{
+ basic_block bb, dominated;
+ VEC (basic_block, heap) *dom_tree_walk;
+ unsigned int dom_tree_walk_index;
+ VEC (basic_block, heap) *domby;
+ unsigned int i,j;
+ struct expr **index_map;
+ struct expr *expr;
+ int *to_bb_head;
+ int *bb_size;
+ int changed = 0;
+
+ /* Compute a mapping from expression number (`bitmap_index') to
+ hash table entry. */
+
+ index_map = XCNEWVEC (struct expr *, expr_hash_table.n_elems);
+ for (i = 0; i < expr_hash_table.size; i++)
+ for (expr = expr_hash_table.table[i]; expr != NULL; expr = expr->next_same_hash)
+ index_map[expr->bitmap_index] = expr;
+
+ /* Calculate sizes of basic blocks and note how far
+ each instruction is from the start of its block. We then use this
+ data to restrict distance an expression can travel. */
+
+ to_bb_head = XCNEWVEC (int, get_max_uid ());
+ bb_size = XCNEWVEC (int, last_basic_block);
+
+ FOR_EACH_BB (bb)
+ {
+ rtx insn;
+ int to_head;
+
+ to_head = 0;
+ FOR_BB_INSNS (bb, insn)
+ {
+ /* Don't count debug instructions to avoid them affecting
+ decision choices. */
+ if (NONDEBUG_INSN_P (insn))
+ to_bb_head[INSN_UID (insn)] = to_head++;
+ }
+
+ bb_size[bb->index] = to_head;
+ }
+
+ gcc_assert (EDGE_COUNT (ENTRY_BLOCK_PTR->succs) == 1
+ && (EDGE_SUCC (ENTRY_BLOCK_PTR, 0)->dest
+ == ENTRY_BLOCK_PTR->next_bb));
+
+ dom_tree_walk = get_all_dominated_blocks (CDI_DOMINATORS,
+ ENTRY_BLOCK_PTR->next_bb);
+
+ /* Walk over each basic block looking for potentially hoistable
+ expressions, nothing gets hoisted from the entry block. */
+ FOR_EACH_VEC_ELT (basic_block, dom_tree_walk, dom_tree_walk_index, bb)
+ {
+ domby = get_dominated_to_depth (CDI_DOMINATORS, bb, MAX_HOIST_DEPTH);
+
+ if (VEC_length (basic_block, domby) == 0)
+ continue;
+
+ /* Examine each expression that is very busy at the exit of this
+ block. These are the potentially hoistable expressions. */
+ for (i = 0; i < hoist_vbeout[bb->index]->n_bits; i++)
+ {
+ if (TEST_BIT (hoist_vbeout[bb->index], i))
+ {
+ /* Current expression. */
+ struct expr *expr = index_map[i];
+ /* Number of occurences of EXPR that can be hoisted to BB. */
+ int hoistable = 0;
+ /* Basic blocks that have occurences reachable from BB. */
+ bitmap_head _from_bbs, *from_bbs = &_from_bbs;
+ /* Occurences reachable from BB. */
+ VEC (occr_t, heap) *occrs_to_hoist = NULL;
+ /* We want to insert the expression into BB only once, so
+ note when we've inserted it. */
+ int insn_inserted_p;
+ occr_t occr;
+
+ bitmap_initialize (from_bbs, 0);
+
+ /* If an expression is computed in BB and is available at end of
+ BB, hoist all occurences dominated by BB to BB. */
+ if (TEST_BIT (comp[bb->index], i))
+ {
+ occr = find_occr_in_bb (expr->antic_occr, bb);
+
+ if (occr)
+ {
+ /* An occurence might've been already deleted
+ while processing a dominator of BB. */
+ if (occr->deleted_p)
+ gcc_assert (MAX_HOIST_DEPTH > 1);
+ else
+ {
+ gcc_assert (NONDEBUG_INSN_P (occr->insn));
+ hoistable++;
+ }
+ }
+ else
+ hoistable++;
+ }
+
+ /* We've found a potentially hoistable expression, now
+ we look at every block BB dominates to see if it
+ computes the expression. */
+ FOR_EACH_VEC_ELT (basic_block, domby, j, dominated)
+ {
+ int max_distance;
+
+ /* Ignore self dominance. */
+ if (bb == dominated)
+ continue;
+ /* We've found a dominated block, now see if it computes
+ the busy expression and whether or not moving that
+ expression to the "beginning" of that block is safe. */
+ if (!TEST_BIT (antloc[dominated->index], i))
+ continue;
+
+ occr = find_occr_in_bb (expr->antic_occr, dominated);
+ gcc_assert (occr);
+
+ /* An occurence might've been already deleted
+ while processing a dominator of BB. */
+ if (occr->deleted_p)
+ {
+ gcc_assert (MAX_HOIST_DEPTH > 1);
+ continue;
+ }
+ gcc_assert (NONDEBUG_INSN_P (occr->insn));
+
+ max_distance = expr->max_distance;
+ if (max_distance > 0)
+ /* Adjust MAX_DISTANCE to account for the fact that
+ OCCR won't have to travel all of DOMINATED, but
+ only part of it. */
+ max_distance += (bb_size[dominated->index]
+ - to_bb_head[INSN_UID (occr->insn)]);
+
+ /* Note if the expression would reach the dominated block
+ unimpared if it was placed at the end of BB.
+
+ Keep track of how many times this expression is hoistable
+ from a dominated block into BB. */
+ if (hoist_expr_reaches_here_p (bb, i, dominated, NULL,
+ max_distance, bb_size))
+ {
+ hoistable++;
+ VEC_safe_push (occr_t, heap,
+ occrs_to_hoist, occr);
+ bitmap_set_bit (from_bbs, dominated->index);
+ }
+ }
+
+ /* If we found more than one hoistable occurrence of this
+ expression, then note it in the vector of expressions to
+ hoist. It makes no sense to hoist things which are computed
+ in only one BB, and doing so tends to pessimize register
+ allocation. One could increase this value to try harder
+ to avoid any possible code expansion due to register
+ allocation issues; however experiments have shown that
+ the vast majority of hoistable expressions are only movable
+ from two successors, so raising this threshold is likely
+ to nullify any benefit we get from code hoisting. */
+ if (hoistable > 1 && dbg_cnt (hoist_insn))
+ {
+ /* If (hoistable != VEC_length), then there is
+ an occurence of EXPR in BB itself. Don't waste
+ time looking for LCA in this case. */
+ if ((unsigned) hoistable
+ == VEC_length (occr_t, occrs_to_hoist))
+ {
+ basic_block lca;
+
+ lca = nearest_common_dominator_for_set (CDI_DOMINATORS,
+ from_bbs);
+ if (lca != bb)
+ /* Punt, it's better to hoist these occurences to
+ LCA. */
+ VEC_free (occr_t, heap, occrs_to_hoist);
+ }
+ }
+ else
+ /* Punt, no point hoisting a single occurence. */
+ VEC_free (occr_t, heap, occrs_to_hoist);
+
+ insn_inserted_p = 0;
+
+ /* Walk through occurences of I'th expressions we want
+ to hoist to BB and make the transformations. */
+ FOR_EACH_VEC_ELT (occr_t, occrs_to_hoist, j, occr)
+ {
+ rtx insn;
+ rtx set;
+
+ gcc_assert (!occr->deleted_p);
+
+ insn = occr->insn;
+ set = single_set (insn);
+ gcc_assert (set);
+
+ /* Create a pseudo-reg to store the result of reaching
+ expressions into. Get the mode for the new pseudo
+ from the mode of the original destination pseudo.
+
+ It is important to use new pseudos whenever we
+ emit a set. This will allow reload to use
+ rematerialization for such registers. */
+ if (!insn_inserted_p)
+ expr->reaching_reg
+ = gen_reg_rtx_and_attrs (SET_DEST (set));
+
+ gcse_emit_move_after (expr->reaching_reg, SET_DEST (set),
+ insn);
+ delete_insn (insn);
+ occr->deleted_p = 1;
+ changed = 1;
+ gcse_subst_count++;
+
+ if (!insn_inserted_p)
+ {
+ insert_insn_end_basic_block (expr, bb);
+ insn_inserted_p = 1;
+ }
+ }
+
+ VEC_free (occr_t, heap, occrs_to_hoist);
+ bitmap_clear (from_bbs);
+ }
+ }
+ VEC_free (basic_block, heap, domby);
+ }
+
+ VEC_free (basic_block, heap, dom_tree_walk);
+ free (bb_size);
+ free (to_bb_head);
+ free (index_map);
+
+ return changed;
+}
+
+/* Top level routine to perform one code hoisting (aka unification) pass
+
+ Return nonzero if a change was made. */
+
+static int
+one_code_hoisting_pass (void)
+{
+ int changed = 0;
+
+ gcse_subst_count = 0;
+ gcse_create_count = 0;
+
+ /* Return if there's nothing to do, or it is too expensive. */
+ if (n_basic_blocks <= NUM_FIXED_BLOCKS + 1
+ || is_too_expensive (_("GCSE disabled")))
+ return 0;
+
+ doing_code_hoisting_p = true;
+
+ /* We need alias. */
+ init_alias_analysis ();
+
+ bytes_used = 0;
+ gcc_obstack_init (&gcse_obstack);
+ alloc_gcse_mem ();
+
+ alloc_hash_table (&expr_hash_table, 0);
+ compute_hash_table (&expr_hash_table);
+ if (dump_file)
+ dump_hash_table (dump_file, "Code Hosting Expressions", &expr_hash_table);
+
+ if (expr_hash_table.n_elems > 0)
+ {
+ alloc_code_hoist_mem (last_basic_block, expr_hash_table.n_elems);
+ compute_code_hoist_data ();
+ changed = hoist_code ();
+ free_code_hoist_mem ();
+ }
+
+ free_hash_table (&expr_hash_table);
+ free_gcse_mem ();
+ obstack_free (&gcse_obstack, NULL);
+
+ /* We are finished with alias. */
+ end_alias_analysis ();
+
+ if (dump_file)
+ {
+ fprintf (dump_file, "HOIST of %s, %d basic blocks, %d bytes needed, ",
+ current_function_name (), n_basic_blocks, bytes_used);
+ fprintf (dump_file, "%d substs, %d insns created\n",
+ gcse_subst_count, gcse_create_count);
+ }
+
+ doing_code_hoisting_p = false;
+
+ return changed;
+}
+
+/* Here we provide the things required to do store motion towards
+ the exit. In order for this to be effective, gcse also needed to
+ be taught how to move a load when it is kill only by a store to itself.
+
+ int i;
+ float a[10];
+
+ void foo(float scale)
+ {
+ for (i=0; i<10; i++)
+ a[i] *= scale;
+ }
+
+ 'i' is both loaded and stored to in the loop. Normally, gcse cannot move
+ the load out since its live around the loop, and stored at the bottom
+ of the loop.
+
+ The 'Load Motion' referred to and implemented in this file is
+ an enhancement to gcse which when using edge based lcm, recognizes
+ this situation and allows gcse to move the load out of the loop.
+
+ Once gcse has hoisted the load, store motion can then push this
+ load towards the exit, and we end up with no loads or stores of 'i'
+ in the loop. */
+
+static hashval_t
+pre_ldst_expr_hash (const void *p)
+{
+ int do_not_record_p = 0;
+ const struct ls_expr *const x = (const struct ls_expr *) p;
+ return hash_rtx (x->pattern, GET_MODE (x->pattern), &do_not_record_p, NULL, false);
+}
+
+static int
+pre_ldst_expr_eq (const void *p1, const void *p2)
+{
+ const struct ls_expr *const ptr1 = (const struct ls_expr *) p1,
+ *const ptr2 = (const struct ls_expr *) p2;
+ return expr_equiv_p (ptr1->pattern, ptr2->pattern);
+}
+
+/* This will search the ldst list for a matching expression. If it
+ doesn't find one, we create one and initialize it. */
+
+static struct ls_expr *
+ldst_entry (rtx x)
+{
+ int do_not_record_p = 0;
+ struct ls_expr * ptr;
+ unsigned int hash;
+ void **slot;
+ struct ls_expr e;
+
+ hash = hash_rtx (x, GET_MODE (x), &do_not_record_p,
+ NULL, /*have_reg_qty=*/false);
+
+ e.pattern = x;
+ slot = htab_find_slot_with_hash (pre_ldst_table, &e, hash, INSERT);
+ if (*slot)
+ return (struct ls_expr *)*slot;
+
+ ptr = XNEW (struct ls_expr);
+
+ ptr->next = pre_ldst_mems;
+ ptr->expr = NULL;
+ ptr->pattern = x;
+ ptr->pattern_regs = NULL_RTX;
+ ptr->loads = NULL_RTX;
+ ptr->stores = NULL_RTX;
+ ptr->reaching_reg = NULL_RTX;
+ ptr->invalid = 0;
+ ptr->index = 0;
+ ptr->hash_index = hash;
+ pre_ldst_mems = ptr;
+ *slot = ptr;
+
+ return ptr;
+}
+
+/* Free up an individual ldst entry. */
+
+static void
+free_ldst_entry (struct ls_expr * ptr)
+{
+ free_INSN_LIST_list (& ptr->loads);
+ free_INSN_LIST_list (& ptr->stores);
+
+ free (ptr);
+}
+
+/* Free up all memory associated with the ldst list. */
+
+static void
+free_ldst_mems (void)
+{
+ if (pre_ldst_table)
+ htab_delete (pre_ldst_table);
+ pre_ldst_table = NULL;
+
+ while (pre_ldst_mems)
+ {
+ struct ls_expr * tmp = pre_ldst_mems;
+
+ pre_ldst_mems = pre_ldst_mems->next;
+
+ free_ldst_entry (tmp);
+ }
+
+ pre_ldst_mems = NULL;
+}
+
+/* Dump debugging info about the ldst list. */
+
+static void
+print_ldst_list (FILE * file)
+{
+ struct ls_expr * ptr;
+
+ fprintf (file, "LDST list: \n");
+
+ for (ptr = first_ls_expr (); ptr != NULL; ptr = next_ls_expr (ptr))
+ {
+ fprintf (file, " Pattern (%3d): ", ptr->index);
+
+ print_rtl (file, ptr->pattern);
+
+ fprintf (file, "\n Loads : ");
+
+ if (ptr->loads)
+ print_rtl (file, ptr->loads);
+ else
+ fprintf (file, "(nil)");
+
+ fprintf (file, "\n Stores : ");
+
+ if (ptr->stores)
+ print_rtl (file, ptr->stores);
+ else
+ fprintf (file, "(nil)");
+
+ fprintf (file, "\n\n");
+ }
+
+ fprintf (file, "\n");
+}
+
+/* Returns 1 if X is in the list of ldst only expressions. */
+
+static struct ls_expr *
+find_rtx_in_ldst (rtx x)
+{
+ struct ls_expr e;
+ void **slot;
+ if (!pre_ldst_table)
+ return NULL;
+ e.pattern = x;
+ slot = htab_find_slot (pre_ldst_table, &e, NO_INSERT);
+ if (!slot || ((struct ls_expr *)*slot)->invalid)
+ return NULL;
+ return (struct ls_expr *) *slot;
+}
+
+/* Return first item in the list. */
+
+static inline struct ls_expr *
+first_ls_expr (void)
+{
+ return pre_ldst_mems;
+}
+
+/* Return the next item in the list after the specified one. */
+
+static inline struct ls_expr *
+next_ls_expr (struct ls_expr * ptr)
+{
+ return ptr->next;
+}
+
+/* Load Motion for loads which only kill themselves. */
+
+/* Return true if x is a simple MEM operation, with no registers or
+ side effects. These are the types of loads we consider for the
+ ld_motion list, otherwise we let the usual aliasing take care of it. */
+
+static int
+simple_mem (const_rtx x)
+{
+ if (! MEM_P (x))
+ return 0;
+
+ if (MEM_VOLATILE_P (x))
+ return 0;
+
+ if (GET_MODE (x) == BLKmode)
+ return 0;
+
+ /* If we are handling exceptions, we must be careful with memory references
+ that may trap. If we are not, the behavior is undefined, so we may just
+ continue. */
+ if (cfun->can_throw_non_call_exceptions && may_trap_p (x))
+ return 0;
+
+ if (side_effects_p (x))
+ return 0;
+
+ /* Do not consider function arguments passed on stack. */
+ if (reg_mentioned_p (stack_pointer_rtx, x))
+ return 0;
+
+ if (flag_float_store && FLOAT_MODE_P (GET_MODE (x)))
+ return 0;
+
+ return 1;
+}
+
+/* Make sure there isn't a buried reference in this pattern anywhere.
+ If there is, invalidate the entry for it since we're not capable
+ of fixing it up just yet.. We have to be sure we know about ALL
+ loads since the aliasing code will allow all entries in the
+ ld_motion list to not-alias itself. If we miss a load, we will get
+ the wrong value since gcse might common it and we won't know to
+ fix it up. */
+
+static void
+invalidate_any_buried_refs (rtx x)
+{
+ const char * fmt;
+ int i, j;
+ struct ls_expr * ptr;
+
+ /* Invalidate it in the list. */
+ if (MEM_P (x) && simple_mem (x))
+ {
+ ptr = ldst_entry (x);
+ ptr->invalid = 1;
+ }
+
+ /* Recursively process the insn. */
+ fmt = GET_RTX_FORMAT (GET_CODE (x));
+
+ for (i = GET_RTX_LENGTH (GET_CODE (x)) - 1; i >= 0; i--)
+ {
+ if (fmt[i] == 'e')
+ invalidate_any_buried_refs (XEXP (x, i));
+ else if (fmt[i] == 'E')
+ for (j = XVECLEN (x, i) - 1; j >= 0; j--)
+ invalidate_any_buried_refs (XVECEXP (x, i, j));
+ }
+}
+
+/* Find all the 'simple' MEMs which are used in LOADs and STORES. Simple
+ being defined as MEM loads and stores to symbols, with no side effects
+ and no registers in the expression. For a MEM destination, we also
+ check that the insn is still valid if we replace the destination with a
+ REG, as is done in update_ld_motion_stores. If there are any uses/defs
+ which don't match this criteria, they are invalidated and trimmed out
+ later. */
+
+static void
+compute_ld_motion_mems (void)
+{
+ struct ls_expr * ptr;
+ basic_block bb;
+ rtx insn;
+
+ pre_ldst_mems = NULL;
+ pre_ldst_table = htab_create (13, pre_ldst_expr_hash,
+ pre_ldst_expr_eq, NULL);
+
+ FOR_EACH_BB (bb)
+ {
+ FOR_BB_INSNS (bb, insn)
+ {
+ if (NONDEBUG_INSN_P (insn))
+ {
+ if (GET_CODE (PATTERN (insn)) == SET)
+ {
+ rtx src = SET_SRC (PATTERN (insn));
+ rtx dest = SET_DEST (PATTERN (insn));
+
+ /* Check for a simple LOAD... */
+ if (MEM_P (src) && simple_mem (src))
+ {
+ ptr = ldst_entry (src);
+ if (REG_P (dest))
+ ptr->loads = alloc_INSN_LIST (insn, ptr->loads);
+ else
+ ptr->invalid = 1;
+ }
+ else
+ {
+ /* Make sure there isn't a buried load somewhere. */
+ invalidate_any_buried_refs (src);
+ }
+
+ /* Check for stores. Don't worry about aliased ones, they
+ will block any movement we might do later. We only care
+ about this exact pattern since those are the only
+ circumstance that we will ignore the aliasing info. */
+ if (MEM_P (dest) && simple_mem (dest))
+ {
+ ptr = ldst_entry (dest);
+
+ if (! MEM_P (src)
+ && GET_CODE (src) != ASM_OPERANDS
+ /* Check for REG manually since want_to_gcse_p
+ returns 0 for all REGs. */
+ && can_assign_to_reg_without_clobbers_p (src))
+ ptr->stores = alloc_INSN_LIST (insn, ptr->stores);
+ else
+ ptr->invalid = 1;
+ }
+ }
+ else
+ invalidate_any_buried_refs (PATTERN (insn));
+ }
+ }
+ }
+}
+
+/* Remove any references that have been either invalidated or are not in the
+ expression list for pre gcse. */
+
+static void
+trim_ld_motion_mems (void)
+{
+ struct ls_expr * * last = & pre_ldst_mems;
+ struct ls_expr * ptr = pre_ldst_mems;
+
+ while (ptr != NULL)
+ {
+ struct expr * expr;
+
+ /* Delete if entry has been made invalid. */
+ if (! ptr->invalid)
+ {
+ /* Delete if we cannot find this mem in the expression list. */
+ unsigned int hash = ptr->hash_index % expr_hash_table.size;
+
+ for (expr = expr_hash_table.table[hash];
+ expr != NULL;
+ expr = expr->next_same_hash)
+ if (expr_equiv_p (expr->expr, ptr->pattern))
+ break;
+ }
+ else
+ expr = (struct expr *) 0;
+
+ if (expr)
+ {
+ /* Set the expression field if we are keeping it. */
+ ptr->expr = expr;
+ last = & ptr->next;
+ ptr = ptr->next;
+ }
+ else
+ {
+ *last = ptr->next;
+ htab_remove_elt_with_hash (pre_ldst_table, ptr, ptr->hash_index);
+ free_ldst_entry (ptr);
+ ptr = * last;
+ }
+ }
+
+ /* Show the world what we've found. */
+ if (dump_file && pre_ldst_mems != NULL)
+ print_ldst_list (dump_file);
+}
+
+/* This routine will take an expression which we are replacing with
+ a reaching register, and update any stores that are needed if
+ that expression is in the ld_motion list. Stores are updated by
+ copying their SRC to the reaching register, and then storing
+ the reaching register into the store location. These keeps the
+ correct value in the reaching register for the loads. */
+
+static void
+update_ld_motion_stores (struct expr * expr)
+{
+ struct ls_expr * mem_ptr;
+
+ if ((mem_ptr = find_rtx_in_ldst (expr->expr)))
+ {
+ /* We can try to find just the REACHED stores, but is shouldn't
+ matter to set the reaching reg everywhere... some might be
+ dead and should be eliminated later. */
+
+ /* We replace (set mem expr) with (set reg expr) (set mem reg)
+ where reg is the reaching reg used in the load. We checked in
+ compute_ld_motion_mems that we can replace (set mem expr) with
+ (set reg expr) in that insn. */
+ rtx list = mem_ptr->stores;
+
+ for ( ; list != NULL_RTX; list = XEXP (list, 1))
+ {
+ rtx insn = XEXP (list, 0);
+ rtx pat = PATTERN (insn);
+ rtx src = SET_SRC (pat);
+ rtx reg = expr->reaching_reg;
+ rtx copy;
+
+ /* If we've already copied it, continue. */
+ if (expr->reaching_reg == src)
+ continue;
+
+ if (dump_file)
+ {
+ fprintf (dump_file, "PRE: store updated with reaching reg ");
+ print_rtl (dump_file, expr->reaching_reg);
+ fprintf (dump_file, ":\n ");
+ print_inline_rtx (dump_file, insn, 8);
+ fprintf (dump_file, "\n");
+ }
+
+ copy = gen_move_insn (reg, copy_rtx (SET_SRC (pat)));
+ emit_insn_before (copy, insn);
+ SET_SRC (pat) = reg;
+ df_insn_rescan (insn);
+
+ /* un-recognize this pattern since it's probably different now. */
+ INSN_CODE (insn) = -1;
+ gcse_create_count++;
+ }
+ }
+}
+
+/* Return true if the graph is too expensive to optimize. PASS is the
+ optimization about to be performed. */
+
+static bool
+is_too_expensive (const char *pass)
+{
+ /* Trying to perform global optimizations on flow graphs which have
+ a high connectivity will take a long time and is unlikely to be
+ particularly useful.
+
+ In normal circumstances a cfg should have about twice as many
+ edges as blocks. But we do not want to punish small functions
+ which have a couple switch statements. Rather than simply
+ threshold the number of blocks, uses something with a more
+ graceful degradation. */
+ if (n_edges > 20000 + n_basic_blocks * 4)
+ {
+ warning (OPT_Wdisabled_optimization,
+ "%s: %d basic blocks and %d edges/basic block",
+ pass, n_basic_blocks, n_edges / n_basic_blocks);
+
+ return true;
+ }
+
+ /* If allocating memory for the cprop bitmap would take up too much
+ storage it's better just to disable the optimization. */
+ if ((n_basic_blocks
+ * SBITMAP_SET_SIZE (max_reg_num ())
+ * sizeof (SBITMAP_ELT_TYPE)) > MAX_GCSE_MEMORY)
+ {
+ warning (OPT_Wdisabled_optimization,
+ "%s: %d basic blocks and %d registers",
+ pass, n_basic_blocks, max_reg_num ());
+
+ return true;
+ }
+
+ return false;
+}
+
+
+/* Main function for the CPROP pass. */
+
+static int
+one_cprop_pass (void)
+{
+ int changed = 0;
+
+ /* Return if there's nothing to do, or it is too expensive. */
+ if (n_basic_blocks <= NUM_FIXED_BLOCKS + 1
+ || is_too_expensive (_ ("const/copy propagation disabled")))
+ return 0;
+
+ global_const_prop_count = local_const_prop_count = 0;
+ global_copy_prop_count = local_copy_prop_count = 0;
+
+ bytes_used = 0;
+ gcc_obstack_init (&gcse_obstack);
+ alloc_gcse_mem ();
+
+ /* Do a local const/copy propagation pass first. The global pass
+ only handles global opportunities.
+ If the local pass changes something, remove any unreachable blocks
+ because the CPROP global dataflow analysis may get into infinite
+ loops for CFGs with unreachable blocks.
+
+ FIXME: This local pass should not be necessary after CSE (but for
+ some reason it still is). It is also (proven) not necessary
+ to run the local pass right after FWPWOP.
+
+ FIXME: The global analysis would not get into infinite loops if it
+ would use the DF solver (via df_simple_dataflow) instead of
+ the solver implemented in this file. */
+ if (local_cprop_pass ())
+ {
+ delete_unreachable_blocks ();
+ df_analyze ();
+ }
+
+ /* Determine implicit sets. */
+ implicit_sets = XCNEWVEC (rtx, last_basic_block);
+ find_implicit_sets ();
+
+ alloc_hash_table (&set_hash_table, 1);
+ compute_hash_table (&set_hash_table);
+
+ /* Free implicit_sets before peak usage. */
+ free (implicit_sets);
+ implicit_sets = NULL;
+
+ if (dump_file)
+ dump_hash_table (dump_file, "SET", &set_hash_table);
+ if (set_hash_table.n_elems > 0)
+ {
+ basic_block bb;
+ rtx insn;
+
+ alloc_cprop_mem (last_basic_block, set_hash_table.n_elems);
+ compute_cprop_data ();
+
+ FOR_BB_BETWEEN (bb, ENTRY_BLOCK_PTR->next_bb->next_bb, EXIT_BLOCK_PTR, next_bb)
+ {
+ /* Reset tables used to keep track of what's still valid [since
+ the start of the block]. */
+ reset_opr_set_tables ();
+
+ FOR_BB_INSNS (bb, insn)
+ if (INSN_P (insn))
+ {
+ changed |= cprop_insn (insn);
+
+ /* Keep track of everything modified by this insn. */
+ /* ??? Need to be careful w.r.t. mods done to INSN.
+ Don't call mark_oprs_set if we turned the
+ insn into a NOTE. */
+ if (! NOTE_P (insn))
+ mark_oprs_set (insn);
+ }
+ }
+
+ changed |= bypass_conditional_jumps ();
+ free_cprop_mem ();
+ }
+
+ free_hash_table (&set_hash_table);
+ free_gcse_mem ();
+ obstack_free (&gcse_obstack, NULL);
+
+ if (dump_file)
+ {
+ fprintf (dump_file, "CPROP of %s, %d basic blocks, %d bytes needed, ",
+ current_function_name (), n_basic_blocks, bytes_used);
+ fprintf (dump_file, "%d local const props, %d local copy props, ",
+ local_const_prop_count, local_copy_prop_count);
+ fprintf (dump_file, "%d global const props, %d global copy props\n\n",
+ global_const_prop_count, global_copy_prop_count);
+ }
+
+ return changed;
+}
+
+
+/* All the passes implemented in this file. Each pass has its
+ own gate and execute function, and at the end of the file a
+ pass definition for passes.c.
+
+ We do not construct an accurate cfg in functions which call
+ setjmp, so none of these passes runs if the function calls
+ setjmp.
+ FIXME: Should just handle setjmp via REG_SETJMP notes. */
+
+static bool
+gate_rtl_cprop (void)
+{
+ return optimize > 0 && flag_gcse
+ && !cfun->calls_setjmp
+ && dbg_cnt (cprop);
+}
+
+static unsigned int
+execute_rtl_cprop (void)
+{
+ int changed;
+ delete_unreachable_blocks ();
+ df_set_flags (DF_LR_RUN_DCE);
+ df_analyze ();
+ changed = one_cprop_pass ();
+ flag_rerun_cse_after_global_opts |= changed;
+ if (changed)
+ cleanup_cfg (0);
+ return 0;
+}
+
+static bool
+gate_rtl_pre (void)
+{
+ return optimize > 0 && flag_gcse
+ && !cfun->calls_setjmp
+ && optimize_function_for_speed_p (cfun)
+ && dbg_cnt (pre);
+}
+
+static unsigned int
+execute_rtl_pre (void)
+{
+ int changed;
+ delete_unreachable_blocks ();
+ df_analyze ();
+ changed = one_pre_gcse_pass ();
+ flag_rerun_cse_after_global_opts |= changed;
+ if (changed)
+ cleanup_cfg (0);
+ return 0;
+}
+
+static bool
+gate_rtl_hoist (void)
+{
+ return optimize > 0 && flag_gcse
+ && !cfun->calls_setjmp
+ /* It does not make sense to run code hoisting unless we are optimizing
+ for code size -- it rarely makes programs faster, and can make then
+ bigger if we did PRE (when optimizing for space, we don't run PRE). */
+ && optimize_function_for_size_p (cfun)
+ && dbg_cnt (hoist);
+}
+
+static unsigned int
+execute_rtl_hoist (void)
+{
+ int changed;
+ delete_unreachable_blocks ();
+ df_analyze ();
+ changed = one_code_hoisting_pass ();
+ flag_rerun_cse_after_global_opts |= changed;
+ if (changed)
+ cleanup_cfg (0);
+ return 0;
+}
+
+struct rtl_opt_pass pass_rtl_cprop =
+{
+ {
+ RTL_PASS,
+ "cprop", /* name */
+ gate_rtl_cprop, /* gate */
+ execute_rtl_cprop, /* execute */
+ NULL, /* sub */
+ NULL, /* next */
+ 0, /* static_pass_number */
+ TV_CPROP, /* tv_id */
+ PROP_cfglayout, /* properties_required */
+ 0, /* properties_provided */
+ 0, /* properties_destroyed */
+ 0, /* todo_flags_start */
+ TODO_df_finish | TODO_verify_rtl_sharing |
+ TODO_dump_func |
+ TODO_verify_flow | TODO_ggc_collect /* todo_flags_finish */
+ }
+};
+
+struct rtl_opt_pass pass_rtl_pre =
+{
+ {
+ RTL_PASS,
+ "rtl pre", /* name */
+ gate_rtl_pre, /* gate */
+ execute_rtl_pre, /* execute */
+ NULL, /* sub */
+ NULL, /* next */
+ 0, /* static_pass_number */
+ TV_PRE, /* tv_id */
+ PROP_cfglayout, /* properties_required */
+ 0, /* properties_provided */
+ 0, /* properties_destroyed */
+ 0, /* todo_flags_start */
+ TODO_df_finish | TODO_verify_rtl_sharing |
+ TODO_dump_func |
+ TODO_verify_flow | TODO_ggc_collect /* todo_flags_finish */
+ }
+};
+
+struct rtl_opt_pass pass_rtl_hoist =
+{
+ {
+ RTL_PASS,
+ "hoist", /* name */
+ gate_rtl_hoist, /* gate */
+ execute_rtl_hoist, /* execute */
+ NULL, /* sub */
+ NULL, /* next */
+ 0, /* static_pass_number */
+ TV_HOIST, /* tv_id */
+ PROP_cfglayout, /* properties_required */
+ 0, /* properties_provided */
+ 0, /* properties_destroyed */
+ 0, /* todo_flags_start */
+ TODO_df_finish | TODO_verify_rtl_sharing |
+ TODO_dump_func |
+ TODO_verify_flow | TODO_ggc_collect /* todo_flags_finish */
+ }
+};
+
+#include "gt-gcse.h"
+