mirror of
git://gcc.gnu.org/git/gcc.git
synced 2025-04-13 11:21:18 +08:00
predict.c: New file.
Thu Jan 13 14:46:03 2000 Jason Eckhardt <jle@cygnus.com>
Stan Cox <scox@cygnus.com>
* predict.c: New file. Preliminary infrastructure work for static
branch prediction and basic block reordering.
* basic-block.h: Add prototype for estimate_probability.
* Makefile.in: Add rules for predict.o.
Co-Authored-By: Stan Cox <scox@cygnus.com>
From-SVN: r31402
This commit is contained in:
Jason Eckhardt
Jason Eckhardt
parent
91baa91841
commit
f1ebdfc52a
@ -1,3 +1,11 @@
|
||||
Thu Jan 13 14:46:03 2000 Jason Eckhardt <jle@cygnus.com>
|
||||
Stan Cox <scox@cygnus.com>
|
||||
|
||||
* predict.c: New file. Preliminary infrastructure work for static
|
||||
branch prediction and basic block reordering.
|
||||
* basic-block.h: Add prototype for estimate_probability.
|
||||
* Makefile.in: Add rules for predict.o.
|
||||
|
||||
2000-01-13 Jason Merrill <jason@yorick.cygnus.com>
|
||||
|
||||
* fixincludes (va_list): Use __not_va_list__ for the dummy.
|
||||
|
||||
@ -673,7 +673,7 @@ OBJS = diagnostic.o \
|
||||
insn-opinit.o insn-recog.o insn-extract.o insn-output.o insn-emit.o lcm.o \
|
||||
profile.o insn-attrtab.o $(out_object_file) $(EXTRA_OBJS) convert.o \
|
||||
mbchar.o dyn-string.o splay-tree.o graph.o sbitmap.o resource.o hash.o \
|
||||
lists.o ggc-common.o $(GGC) simplify-rtx.o
|
||||
predict.o lists.o ggc-common.o $(GGC) simplify-rtx.o
|
||||
|
||||
# GEN files are listed separately, so they can be built before doing parallel
|
||||
# makes for cc1 or cc1plus. Otherwise sequent parallel make attempts to load
|
||||
@ -1620,6 +1620,9 @@ reg-stack.o : reg-stack.c $(CONFIG_H) system.h $(RTL_H) $(TREE_H) $(RECOG_H) \
|
||||
$(REGS_H) hard-reg-set.h flags.h insn-config.h insn-flags.h toplev.h \
|
||||
varray.h function.h
|
||||
dyn-string.o: dyn-string.c dyn-string.h $(CONFIG_H) system.h
|
||||
predict.o: predict.c $(CONFIG_H) system.h $(RTL_H) $(TREE_H) flags.h \
|
||||
insn-config.h $(BASIC_BLOCK_H) $(REGS_H) hard-reg-set.h output.h toplev.h \
|
||||
$(RECOG_H) insn-flags.h function.h except.h expr.h
|
||||
lists.o: lists.c $(CONFIG_H) system.h toplev.h $(RTL_H) ggc.h
|
||||
|
||||
$(out_object_file): $(out_file) $(CONFIG_H) $(TREE_H) ggc.h \
|
||||
|
||||
@ -384,4 +384,7 @@ extern void compute_available PARAMS ((sbitmap *, sbitmap *,
|
||||
extern rtx emit_block_insn_after PARAMS ((rtx, rtx, basic_block));
|
||||
extern rtx emit_block_insn_before PARAMS ((rtx, rtx, basic_block));
|
||||
|
||||
/* In predict.c */
|
||||
extern void estimate_probability PARAMS ((struct loops *));
|
||||
|
||||
#endif /* _BASIC_BLOCK_H */
|
||||
|
||||
143
gcc/predict.c
Normal file
143
gcc/predict.c
Normal file
@ -0,0 +1,143 @@
|
||||
/* Branch prediction routines for the GNU compiler.
|
||||
Copyright (C) 2000 Free Software Foundation, Inc.
|
||||
|
||||
This file is part of GNU CC.
|
||||
|
||||
GNU CC 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 2, or (at your option)
|
||||
any later version.
|
||||
|
||||
GNU CC 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 GNU CC; see the file COPYING. If not, write to
|
||||
the Free Software Foundation, 59 Temple Place - Suite 330,
|
||||
Boston, MA 02111-1307, USA. */
|
||||
|
||||
/* References:
|
||||
|
||||
[1] "Branch Prediction for Free"
|
||||
Ball and Larus; PLDI '93.
|
||||
[2] "Static Branch Frequency and Program Profile Analysis"
|
||||
Wu and Larus; MICRO-27.
|
||||
[3] "Corpus-based Static Branch Prediction"
|
||||
Calder, Grunwald, Lindsay, Martin, Mozer, and Zorn; PLDI '95.
|
||||
*/
|
||||
|
||||
|
||||
#include "config.h"
|
||||
#include "system.h"
|
||||
#include "tree.h"
|
||||
#include "rtl.h"
|
||||
#include "tm_p.h"
|
||||
#include "basic-block.h"
|
||||
#include "insn-config.h"
|
||||
#include "regs.h"
|
||||
#include "hard-reg-set.h"
|
||||
#include "flags.h"
|
||||
#include "output.h"
|
||||
#include "function.h"
|
||||
#include "except.h"
|
||||
#include "toplev.h"
|
||||
#include "recog.h"
|
||||
#include "insn-flags.h"
|
||||
#include "expr.h"
|
||||
|
||||
|
||||
|
||||
/* Statically estimate the probability that a branch will be taken.
|
||||
??? In the next revision there will be a number of other predictors added
|
||||
from the above references. Further, each heuristic will be factored out
|
||||
into its own function for clarity (and to facilitate the combination of
|
||||
predictions). */
|
||||
|
||||
void
|
||||
estimate_probability (loops_info)
|
||||
struct loops *loops_info;
|
||||
{
|
||||
int i;
|
||||
|
||||
/* Try to predict out blocks in a loop that are not part of a natural loop */
|
||||
for (i = 0; i < loops_info->num; i++)
|
||||
{
|
||||
int j;
|
||||
|
||||
for (j = loops_info->array[i].header->index;
|
||||
j <= loops_info->array[i].latch->index;
|
||||
++j)
|
||||
{
|
||||
edge e;
|
||||
|
||||
if (! TEST_BIT (loops_info->array[i].nodes, j))
|
||||
for (e = BASIC_BLOCK(j)->pred; e; e = e->pred_next)
|
||||
if (TEST_BIT (loops_info->array[i].nodes, e->src->index))
|
||||
{
|
||||
rtx last_insn = BLOCK_END (e->src->index);
|
||||
rtx cond, earliest;
|
||||
|
||||
if (GET_CODE (last_insn) != JUMP_INSN
|
||||
|| ! condjump_p (last_insn) || simplejump_p (last_insn))
|
||||
continue;
|
||||
cond = get_condition (last_insn, &earliest);
|
||||
if (!cond)
|
||||
continue;
|
||||
if (! find_reg_note (last_insn, REG_BR_PROB, 0))
|
||||
REG_NOTES (last_insn)
|
||||
= gen_rtx_EXPR_LIST (REG_BR_PROB, GEN_INT (REG_BR_PROB_BASE),
|
||||
REG_NOTES (last_insn));
|
||||
}
|
||||
}
|
||||
}
|
||||
|
||||
/* Try to predict condjumps using same algorithm as mostly_true_jump */
|
||||
for (i = 0; i < n_basic_blocks - 1; i++)
|
||||
{
|
||||
rtx last_insn = BLOCK_END (i);
|
||||
rtx cond, earliest;
|
||||
int prob = 0;
|
||||
|
||||
if (GET_CODE (last_insn) != JUMP_INSN
|
||||
|| ! condjump_p (last_insn) || simplejump_p (last_insn))
|
||||
continue;
|
||||
cond = get_condition (last_insn, &earliest);
|
||||
if (! cond)
|
||||
continue;
|
||||
/* EQ tests are usually false and NE tests are usually true. Also,
|
||||
most quantities are positive, so we can make the appropriate guesses
|
||||
about signed comparisons against zero. */
|
||||
switch (GET_CODE (cond))
|
||||
{
|
||||
case CONST_INT:
|
||||
/* Unconditional branch. */
|
||||
prob = REG_BR_PROB_BASE / 2;
|
||||
case EQ:
|
||||
prob = REG_BR_PROB_BASE / 10;
|
||||
case NE:
|
||||
prob = REG_BR_PROB_BASE / 2;
|
||||
case LE:
|
||||
case LT:
|
||||
if (XEXP (cond, 1) == const0_rtx)
|
||||
prob = REG_BR_PROB_BASE / 10;
|
||||
break;
|
||||
case GE:
|
||||
case GT:
|
||||
if (XEXP (cond, 1) == const0_rtx
|
||||
|| (GET_CODE (XEXP (cond, 1)) == CONST_INT
|
||||
&& INTVAL (XEXP (cond, 1)) == -1))
|
||||
prob = REG_BR_PROB_BASE / 2;
|
||||
break;
|
||||
|
||||
default:
|
||||
prob = 0;
|
||||
}
|
||||
if (! find_reg_note (last_insn, REG_BR_PROB, 0))
|
||||
REG_NOTES (last_insn)
|
||||
= gen_rtx_EXPR_LIST (REG_BR_PROB, GEN_INT (prob),
|
||||
REG_NOTES (last_insn));
|
||||
}
|
||||
}
|
||||
|
||||
Loading…
x
Reference in New Issue
Block a user