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combine_stack_adjustments patch
- To: gcc-patches at gcc dot gnu dot org
- Subject: combine_stack_adjustments patch
- From: Richard Henderson <rth at cygnus dot com>
- Date: Mon, 20 Mar 2000 14:51:32 -0800
There was a stupid typo in stack_memref_p that caused much of the
optimization it was supposed to do to be ignored. Fixing that
exposed a bug elsewhere that would mis-handle insns like
mov %esp,8(%esp)
that show up in nested function calls.
In private mail, Uli noticed oddities in functions like
int b(int x, int y) { return e(x, y); }
that would get compiled to
subl $12,%esp
addl $12,%esp
jmp e
This happened because there were dead instructions in between
that were later removed by flow2. Fixed by running this pass
after flow2 instead.
Bootstrapped on i686-pc-linux-gnu.
r~
* regmove.c (stack_memref_p): Fix typo, reorg for readability.
(combine_stack_adjustments_for_block): Don't allow sp references
in the side of a set we're not fixing up.
* toplev.c (rest_of_compilation): Run combine_stack_adjustments
after life_analysis.
Index: regmove.c
===================================================================
RCS file: /cvs/gcc/egcs/gcc/regmove.c,v
retrieving revision 1.82
diff -c -p -d -r1.82 regmove.c
*** regmove.c 2000/03/14 14:38:52 1.82
--- regmove.c 2000/03/20 22:42:47
*************** combine_stack_adjustments ()
*** 2116,2129 ****
/* Recognize a MEM of the form (sp) or (plus sp const). */
static int
! stack_memref_p (mem)
! rtx mem;
{
! return (GET_CODE (mem) == MEM
! && (XEXP (mem, 0) == stack_pointer_rtx
! || (GET_CODE (XEXP (mem, 0)) == PLUS
! && XEXP (XEXP (mem, 0), 0) == stack_pointer_rtx
! && GET_CODE (XEXP (XEXP (mem, 0), 0)) == CONST_INT)));
}
/* Recognize either normal single_set or the hack in i386.md for
--- 2116,2136 ----
/* Recognize a MEM of the form (sp) or (plus sp const). */
static int
! stack_memref_p (x)
! rtx x;
{
! if (GET_CODE (x) != MEM)
! return 0;
! x = XEXP (x, 0);
!
! if (x == stack_pointer_rtx)
! return 1;
! if (GET_CODE (x) == PLUS
! && XEXP (x, 0) == stack_pointer_rtx
! && GET_CODE (XEXP (x, 1)) == CONST_INT)
! return 1;
!
! return 0;
}
/* Recognize either normal single_set or the hack in i386.md for
*************** combine_stack_adjustments_for_block (bb)
*** 2330,2343 ****
}
/* Find loads from stack memory and record them. */
! if (last_sp_set && stack_memref_p (src))
{
memlist = record_one_stack_memref (insn, src, memlist);
goto processed;
}
/* Find stores to stack memory and record them. */
! if (last_sp_set && stack_memref_p (dest))
{
memlist = record_one_stack_memref (insn, dest, memlist);
goto processed;
--- 2337,2352 ----
}
/* Find loads from stack memory and record them. */
! if (last_sp_set && stack_memref_p (src)
! && ! reg_mentioned_p (stack_pointer_rtx, dest))
{
memlist = record_one_stack_memref (insn, src, memlist);
goto processed;
}
/* Find stores to stack memory and record them. */
! if (last_sp_set && stack_memref_p (dest)
! && ! reg_mentioned_p (stack_pointer_rtx, src))
{
memlist = record_one_stack_memref (insn, dest, memlist);
goto processed;
*************** combine_stack_adjustments_for_block (bb)
*** 2351,2356 ****
--- 2360,2366 ----
&& GET_CODE (dest) == MEM
&& GET_CODE (XEXP (dest, 0)) == PRE_DEC
&& XEXP (XEXP (dest, 0), 0) == stack_pointer_rtx
+ && ! reg_mentioned_p (stack_pointer_rtx, src)
&& validate_change (insn, &SET_DEST (set),
change_address (dest, VOIDmode,
stack_pointer_rtx), 0))
Index: toplev.c
===================================================================
RCS file: /cvs/gcc/egcs/gcc/toplev.c,v
retrieving revision 1.307
diff -c -p -d -r1.307 toplev.c
*** toplev.c 2000/03/19 05:26:48 1.307
--- toplev.c 2000/03/20 22:42:47
*************** rest_of_compilation (decl)
*** 3555,3570 ****
if (optimize)
{
! TIMEVAR (flow2_time, { cleanup_cfg (insns); });
#ifndef ACCUMULATE_OUTGOING_ARGS
TIMEVAR (flow2_time, { combine_stack_adjustments (); });
#endif
-
- TIMEVAR (flow2_time,
- {
- life_analysis (insns, max_reg_num (), rtl_dump_file, 1);
- });
if (ggc_p)
ggc_collect ();
--- 3555,3569 ----
if (optimize)
{
! TIMEVAR (flow2_time,
! {
! cleanup_cfg (insns);
! life_analysis (insns, max_reg_num (), rtl_dump_file, 1);
! });
#ifndef ACCUMULATE_OUTGOING_ARGS
TIMEVAR (flow2_time, { combine_stack_adjustments (); });
#endif
if (ggc_p)
ggc_collect ();