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Insert memory clobbers before the code that pops variable arrays. 

This prevents the scheduler from moving references to the arrays
below the stack pop.

From-SVN: r56328
This commit is contained in:
Dale Johannesen 2002-08-14 17:41:52 +00:00 committed by Dale Johannesen
parent 615d009f6d
commit 260f91c292
4 changed files with 28 additions and 5 deletions
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8
gcc/ChangeLog
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@ -1,3 +1,11 @@
2002-08-14 Dale Johannesen <dalej@apple.com>
* explow.c (emit_stack_restore): Emit memory clobbers
preceding the stack pop, to prevent the scheduler from
moving refs to variable arrays below this pop.
* reload1.c (reload): Preserve these clobbers for sched2.
* doc/rtl.texi: Document clobber (mem:BLK (scratch)).
2002-08-14 Neil Booth <neil@daikokuya.co.uk>
* c-opts.c (c_common_post_options): Correct test.

3
gcc/doc/rtl.texi
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@ -2294,7 +2294,8 @@ trouble to describe the values that are stored, but it is essential to
inform the compiler that the registers will be altered, lest it
attempt to keep data in them across the string instruction.
If @var{x} is @code{(mem:BLK (const_int 0))}, it means that all memory
If @var{x} is @code{(mem:BLK (const_int 0))} or
@code{(mem:BLK (scratch))}, it means that all memory
locations must be presumed clobbered. If @var{x} is a @code{parallel},
it has the same meaning as a @code{parallel} in a @code{set} expression.

12
gcc/explow.c
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@ -1079,7 +1079,17 @@ emit_stack_restore (save_level, sa, after)
}
if (sa != 0)
sa = validize_mem (sa);
{
sa = validize_mem (sa);
/* These clobbers prevent the scheduler from moving
references to variable arrays below the code
that deletes (pops) the arrays. */
emit_insn (gen_rtx_CLOBBER (VOIDmode,
gen_rtx_MEM (BLKmode,
gen_rtx_SCRATCH (VOIDmode))));
emit_insn (gen_rtx_CLOBBER (VOIDmode,
gen_rtx_MEM (BLKmode, stack_pointer_rtx)));
}
if (after)
{

10
gcc/reload1.c
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@ -1181,9 +1181,11 @@ reload (first, global)
/* Make a pass over all the insns and delete all USEs which we inserted
only to tag a REG_EQUAL note on them. Remove all REG_DEAD and REG_UNUSED
notes. Delete all CLOBBER insns that don't refer to the return value
and simplify (subreg (reg)) operands. Also remove all REG_RETVAL and
REG_LIBCALL notes since they are no longer useful or accurate. Strip
and regenerate REG_INC notes that may have been moved around. */
or to memory (mem:BLK CLOBBERs must be retained to prevent the scheduler
from misarranging variable-array code) and simplify (subreg (reg))
operands. Also remove all REG_RETVAL and REG_LIBCALL notes since they
are no longer useful or accurate. Strip and regenerate REG_INC notes
that may have been moved around. */
for (insn = first; insn; insn = NEXT_INSN (insn))
if (INSN_P (insn))
@ -1200,6 +1202,8 @@ reload (first, global)
&& (GET_MODE (insn) == QImode
|| find_reg_note (insn, REG_EQUAL, NULL_RTX)))
|| (GET_CODE (PATTERN (insn)) == CLOBBER
&& (GET_CODE (XEXP (PATTERN (insn), 0)) != MEM
|| GET_MODE (XEXP (PATTERN (insn), 0)) != BLKmode)
&& (GET_CODE (XEXP (PATTERN (insn), 0)) != REG
|| ! REG_FUNCTION_VALUE_P (XEXP (PATTERN (insn), 0)))))
{