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middle-end/96369 - fix missed short-circuiting during range folding

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This makes the special case of constant evaluated LHS for a
short-circuiting or/and explicit rather than doing range
merging and eventually exposing a side-effect that shouldn't be
evaluated.

2020-07-31  Richard Biener  <rguenther@suse.de>

	PR middle-end/96369
	* fold-const.c (fold_range_test): Special-case constant
	LHS for short-circuiting operations.

	* c-c++-common/pr96369.c: New testcase.
This commit is contained in:
Richard Biener 2020-07-31 08:41:56 +02:00
parent bc2b1a232b
commit 10231958fc
2 changed files with 19 additions and 0 deletions
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7
gcc/fold-const.c
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@ -5931,6 +5931,13 @@ fold_range_test (location_t loc, enum tree_code code, tree type,
return 0;
lhs = make_range (op0, &in0_p, &low0, &high0, &strict_overflow_p);
/* If op0 is known true or false and this is a short-circuiting
operation we must not merge with op1 since that makes side-effects
unconditional. So special-case this. */
if (!lhs
&& ((code == TRUTH_ORIF_EXPR && in0_p)
|| (code == TRUTH_ANDIF_EXPR && !in0_p)))
return op0;
rhs = make_range (op1, &in1_p, &low1, &high1, &strict_overflow_p);
/* If this is an OR operation, invert both sides; we will invert

12
gcc/testsuite/c-c++-common/pr96369.c Normal file
View File

@ -0,0 +1,12 @@
/* { dg-do compile } */
/* { dg-options "-O" } */
int main()
{
const long ONE = 1L;
long y = 0L;
long x = ((long) (ONE || (y = 1L)) % 8L);
if (y != 0)
__builtin_abort ();
return 0;
}