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re PR rtl-optimization/11381 (volatile memory access optimized away)

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PR optimization/11381
	* simplify-rtx.c (simplify_relational_operation): Check that
	two equal operands have no side-effects before simplifying
	the comparison.

From-SVN: r68869
This commit is contained in:
Eric Botcazou 2003-07-03 09:30:03 +02:00 committed by Eric Botcazou
parent 7960bf2230
commit 8821d0914c
4 changed files with 29 additions and 2 deletions
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7
gcc/ChangeLog
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@ -1,3 +1,10 @@
2003-07-03 Eric Botcazou <ebotcazou@libertysurf.fr>
PR optimization/11381
* simplify-rtx.c (simplify_relational_operation): Check that
two equal operands have no side-effects before simplifying
the comparison.
2003-07-02 Jeff Law <law@redhat.com>
* expr.c (do_store_flag): Remove special case folding for

6
gcc/simplify-rtx.c
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@ -2220,8 +2220,10 @@ simplify_relational_operation (code, mode, op0, op1)
return const0_rtx;
/* For modes without NaNs, if the two operands are equal, we know the
result. */
if (!HONOR_NANS (GET_MODE (trueop0)) && rtx_equal_p (trueop0, trueop1))
result except if they have side-effects. */
if (! HONOR_NANS (GET_MODE (trueop0))
&& rtx_equal_p (trueop0, trueop1)
&& ! side_effects_p (trueop0))
equal = 1, op0lt = 0, op0ltu = 0, op1lt = 0, op1ltu = 0;
/* If the operands are floating-point constants, see if we can fold

4
gcc/testsuite/ChangeLog
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@ -1,3 +1,7 @@
2003-07-03 Eric Botcazou <ebotcazou@libertysurf.fr>
* gcc.dg/i386-volatile-1.c: New test.
2003-07-02 Nathan Sidwell <nathan@codesourcery.com>
PR c++/11072

14
gcc/testsuite/gcc.dg/i386-volatile-1.c Normal file
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@ -0,0 +1,14 @@
/* PR optimization/11381 */
/* Originator: <tobias@ringstrom.mine.nu> */
/* { dg-do compile { target i?86-*-* } } */
/* { dg-options "-O" } */
/* Verify that the comparison is not optimized away. */
void foo(volatile unsigned int *vaddr)
{
while (*vaddr != *vaddr)
;
}
/* { dg-final { scan-assembler "cmp" } } */