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re PR rtl-optimization/47925 (delete_trivially_dead_insns mishandles volatile mems)

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gcc/
	PR rtl-optimization/47925
	* cse.c (count_reg_usage): Don't ignore the SET_DEST of instructions
	with side effects.  Remove the more-specific check for volatile asms.

gcc/testsuite/
	PR rtl-optimization/47925
	* gcc.c-torture/execute/pr47925.c: New test.

From-SVN: r170613
This commit is contained in:
Richard Sandiford 2011-03-02 13:25:10 +00:00 committed by Richard Sandiford
parent b2e2ea671c
commit 34161e98f7
4 changed files with 42 additions and 9 deletions
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6
gcc/ChangeLog
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@ -1,3 +1,9 @@
2011-03-02 Richard Sandiford <richard.sandiford@linaro.org>
PR rtl-optimization/47925
* cse.c (count_reg_usage): Don't ignore the SET_DEST of instructions
with side effects. Remove the more-specific check for volatile asms.
2011-03-02 Alan Modra <amodra@gmail.com>
PR target/47935

16
gcc/cse.c
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@ -6575,8 +6575,9 @@ check_for_label_ref (rtx *rtl, void *data)
Don't count a usage of DEST, which is the SET_DEST of a SET which
contains X in its SET_SRC. This is because such a SET does not
modify the liveness of DEST.
DEST is set to pc_rtx for a trapping insn, which means that we must count
uses of a SET_DEST regardless because the insn can't be deleted here. */
DEST is set to pc_rtx for a trapping insn, or for an insn with side effects.
We must then count uses of a SET_DEST regardless, because the insn can't be
deleted here. */
static void
count_reg_usage (rtx x, int *counts, rtx dest, int incr)
@ -6629,9 +6630,10 @@ count_reg_usage (rtx x, int *counts, rtx dest, int incr)
case CALL_INSN:
case INSN:
case JUMP_INSN:
/* We expect dest to be NULL_RTX here. If the insn may trap, mark
this fact by setting DEST to pc_rtx. */
if (insn_could_throw_p (x))
/* We expect dest to be NULL_RTX here. If the insn may trap,
or if it cannot be deleted due to side-effects, mark this fact
by setting DEST to pc_rtx. */
if (insn_could_throw_p (x) || side_effects_p (PATTERN (x)))
dest = pc_rtx;
if (code == CALL_INSN)
count_reg_usage (CALL_INSN_FUNCTION_USAGE (x), counts, dest, incr);
@ -6671,10 +6673,6 @@ count_reg_usage (rtx x, int *counts, rtx dest, int incr)
return;
case ASM_OPERANDS:
/* If the asm is volatile, then this insn cannot be deleted,
and so the inputs *must* be live. */
if (MEM_VOLATILE_P (x))
dest = NULL_RTX;
/* Iterate over just the inputs, not the constraints as well. */
for (i = ASM_OPERANDS_INPUT_LENGTH (x) - 1; i >= 0; i--)
count_reg_usage (ASM_OPERANDS_INPUT (x, i), counts, dest, incr);

5
gcc/testsuite/ChangeLog
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@ -1,3 +1,8 @@
2011-03-02 Richard Sandiford <richard.sandiford@linaro.org>
PR rtl-optimization/47925
* gcc.c-torture/execute/pr47925.c: New test.
2011-03-01 Jason Merrill <jason@redhat.com>
* g++.dg/cpp0x/decltype25.C: New.

24
gcc/testsuite/gcc.c-torture/execute/pr47925.c Normal file
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@ -0,0 +1,24 @@
struct s { volatile struct s *next; };
void __attribute__((noinline))
bar (int ignored, int n)
{
asm volatile ("");
}
int __attribute__((noinline))
foo (volatile struct s *ptr, int n)
{
int i;
bar (0, n);
for (i = 0; i < n; i++)
ptr = ptr->next;
}
int main (void)
{
volatile struct s rec = { &rec };
foo (&rec, 10);
return 0;
}