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middle-end/100672 - fix bogus right shift folding

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This fixes the bogus use of TYPE_PRECISION on vector types
from optimizing -((int)x >> 31) into (unsigned)x >> 31.

2021-05-19  Richard Biener  <rguenther@suse.de>

	PR middle-end/100672
	* fold-const.c (fold_negate_expr_1): Use element_precision.
	(negate_expr_p): Likewise.

	* gcc.dg/torture/pr100672.c: New testcase.

(cherry picked from commit 8d51039cb7)
This commit is contained in:
Richard Biener 2021-05-19 13:35:07 +02:00
parent 49230cc051
commit e0dae9c92a
2 changed files with 21 additions and 2 deletions
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4
gcc/fold-const.c
View File

@ -512,7 +512,7 @@ negate_expr_p (tree t)
if (TREE_CODE (TREE_OPERAND (t, 1)) == INTEGER_CST)
{
tree op1 = TREE_OPERAND (t, 1);
if (wi::to_wide (op1) == TYPE_PRECISION (type) - 1)
if (wi::to_wide (op1) == element_precision (type) - 1)
return true;
}
break;
@ -705,7 +705,7 @@ fold_negate_expr_1 (location_t loc, tree t)
if (TREE_CODE (TREE_OPERAND (t, 1)) == INTEGER_CST)
{
tree op1 = TREE_OPERAND (t, 1);
if (wi::to_wide (op1) == TYPE_PRECISION (type) - 1)
if (wi::to_wide (op1) == element_precision (type) - 1)
{
tree ntype = TYPE_UNSIGNED (type)
? signed_type_for (type)

19
gcc/testsuite/gcc.dg/torture/pr100672.c Normal file
View File

@ -0,0 +1,19 @@
/* { dg-do run } */
/* { dg-additional-options "-w -Wno-psabi" } */
typedef long long __attribute__((__vector_size__ (4 * sizeof (long long)))) V;
V
foo (V v)
{
return -(v >> 1);
}
int
main (void)
{
V v = foo ((V) { -2, -4, -6, -8 });
if (v[0] != 1 || v[1] != 2 || v[2] != 3 || v[3] != 4)
__builtin_abort ();
return 0;
}