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backport: re PR tree-optimization/56250 (Wrong constant folding on unsigned int) 

Backported from mainline
	2013-02-08  Jakub Jelinek  <jakub@redhat.com>

	PR tree-optimization/56250
	* fold-const.c (extract_muldiv_1) <case NEGATE_EXPR>: Don't optimize
	if type is unsigned and code isn't MULT_EXPR.

	* gcc.c-torture/execute/pr56250.c: New test.

From-SVN: r196147
This commit is contained in:
Jakub Jelinek 2013-02-19 18:26:04 +01:00 committed by Jakub Jelinek
parent 953142867a
commit 11ba2b86b5
4 changed files with 29 additions and 0 deletions
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6
gcc/ChangeLog
View File

@ -1,6 +1,12 @@
2013-02-19 Jakub Jelinek <jakub@redhat.com>
Backported from mainline
2013-02-08 Jakub Jelinek <jakub@redhat.com>
PR tree-optimization/56250
* fold-const.c (extract_muldiv_1) <case NEGATE_EXPR>: Don't optimize
if type is unsigned and code isn't MULT_EXPR.
2013-02-06 Jakub Jelinek <jakub@redhat.com>
PR middle-end/56217

5
gcc/fold-const.c
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@ -5716,6 +5716,11 @@ extract_muldiv_1 (tree t, tree c, enum tree_code code, tree wide_type,
break;
/* FALLTHROUGH */
case NEGATE_EXPR:
/* For division and modulus, type can't be unsigned, as e.g.
(-(x / 2U)) / 2U isn't equal to -((x / 2U) / 2U) for x >= 2.
For signed types, even with wrapping overflow, this is fine. */
if (code != MULT_EXPR && TYPE_UNSIGNED (type))
break;
if ((t1 = extract_muldiv (op0, c, code, wide_type, strict_overflow_p))
!= 0)
return fold_build1 (tcode, ctype, fold_convert (ctype, t1));

5
gcc/testsuite/ChangeLog
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@ -1,6 +1,11 @@
2013-02-19 Jakub Jelinek <jakub@redhat.com>
Backported from mainline
2013-02-08 Jakub Jelinek <jakub@redhat.com>
PR tree-optimization/56250
* gcc.c-torture/execute/pr56250.c: New test.
2013-02-07 Jakub Jelinek <jakub@redhat.com>
PR c++/56241

13
gcc/testsuite/gcc.c-torture/execute/pr56250.c Normal file
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@ -0,0 +1,13 @@
/* PR tree-optimization/56250 */
extern void abort (void);
int
main ()
{
unsigned int x = 2;
unsigned int y = (0U - x / 2) / 2;
if (-1U / x != y)
abort ();
return 0;
}