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widening_mul: Fix up signed multiplication overflow check handling [PR98727]

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I forgot one line, which means that if the second operand of the multiplication
isn't constant, it would be just the same as the first one.

2021-01-18  Jakub Jelinek  <jakub@redhat.com>

	PR tree-optimization/98727
	* tree-ssa-math-opts.c (match_arith_overflow): Fix up computation of
	second .MUL_OVERFLOW operand for signed multiplication with overflow
	checking if the second operand of multiplication is not constant.

	* gcc.c-torture/execute/pr98727.c: New test.
This commit is contained in:
Jakub Jelinek 2021-01-18 19:13:44 +01:00
parent f56e14101b
commit 9675ccd64e
2 changed files with 21 additions and 0 deletions
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20
gcc/testsuite/gcc.c-torture/execute/pr98727.c Normal file
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@ -0,0 +1,20 @@
/* PR tree-optimization/98727 */
__attribute__((noipa)) long int
foo (long int x, long int y)
{
long int z = (unsigned long) x * y;
if (x != z / y)
return -1;
return z;
}
int
main ()
{
if (foo (4, 24) != 96
|| foo (124, 126) != 124L * 126
|| foo (__LONG_MAX__ / 16, 17) != -1)
__builtin_abort ();
return 0;
}

1
gcc/tree-ssa-math-opts.c
View File

@ -4170,6 +4170,7 @@ match_arith_overflow (gimple_stmt_iterator *gsi, gimple *stmt,
rhs2 = fold_convert (type, rhs2);
else
{
g = SSA_NAME_DEF_STMT (rhs2);
if (gimple_assign_cast_p (g)
&& useless_type_conversion_p (type,
TREE_TYPE (gimple_assign_rhs1 (g)))