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re PR tree-optimization/57656 (Wrong constant folding) 

2013-09-03  Richard Biener  <rguenther@suse.de>

	PR middle-end/57656
	* fold-const.c (negate_expr_p): Fix division case.
	(negate_expr): Likewise.

	* gcc.dg/torture/pr57656.c: New testcase.

From-SVN: r202204
This commit is contained in:
Richard Biener 2013-09-03 10:00:06 +00:00 committed by Richard Biener
parent 20059c8b38
commit dbfc28948e
4 changed files with 55 additions and 14 deletions
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6
gcc/ChangeLog
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@ -1,3 +1,9 @@
2013-09-03 Richard Biener <rguenther@suse.de>
PR middle-end/57656
* fold-const.c (negate_expr_p): Fix division case.
(negate_expr): Likewise.
2013-09-03 Richard Biener <rguenther@suse.de>
PR lto/58285

45
gcc/fold-const.c
View File

@ -483,11 +483,24 @@ negate_expr_p (tree t)
and actually traps on some architectures. But if overflow is
undefined, we can negate, because - (INT_MIN / 1) is an
overflow. */
if (INTEGRAL_TYPE_P (TREE_TYPE (t))
&& !TYPE_OVERFLOW_UNDEFINED (TREE_TYPE (t)))
break;
return negate_expr_p (TREE_OPERAND (t, 1))
|| negate_expr_p (TREE_OPERAND (t, 0));
if (INTEGRAL_TYPE_P (TREE_TYPE (t)))
{
if (!TYPE_OVERFLOW_UNDEFINED (TREE_TYPE (t)))
break;
/* If overflow is undefined then we have to be careful because
we ask whether it's ok to associate the negate with the
division which is not ok for example for
-((a - b) / c) where (-(a - b)) / c may invoke undefined
overflow because of negating INT_MIN. So do not use
negate_expr_p here but open-code the two important cases. */
if (TREE_CODE (TREE_OPERAND (t, 0)) == NEGATE_EXPR
|| (TREE_CODE (TREE_OPERAND (t, 0)) == INTEGER_CST
&& may_negate_without_overflow_p (TREE_OPERAND (t, 0))))
return true;
}
else if (negate_expr_p (TREE_OPERAND (t, 0)))
return true;
return negate_expr_p (TREE_OPERAND (t, 1));
case NOP_EXPR:
/* Negate -((double)float) as (double)(-float). */
@ -682,16 +695,20 @@ fold_negate_expr (location_t loc, tree t)
return fold_build2_loc (loc, TREE_CODE (t), type,
TREE_OPERAND (t, 0), negate_expr (tem));
}
/* If overflow is undefined then we have to be careful because
we ask whether it's ok to associate the negate with the
division which is not ok for example for
-((a - b) / c) where (-(a - b)) / c may invoke undefined
overflow because of negating INT_MIN. So do not use
negate_expr_p here but open-code the two important cases. */
tem = TREE_OPERAND (t, 0);
if (negate_expr_p (tem))
{
if (INTEGRAL_TYPE_P (type)
&& (TREE_CODE (tem) != INTEGER_CST
|| tree_int_cst_equal (tem, TYPE_MIN_VALUE (type))))
fold_overflow_warning (warnmsg, WARN_STRICT_OVERFLOW_MISC);
return fold_build2_loc (loc, TREE_CODE (t), type,
negate_expr (tem), TREE_OPERAND (t, 1));
}
if ((INTEGRAL_TYPE_P (type)
&& (TREE_CODE (tem) == NEGATE_EXPR
|| (TREE_CODE (tem) == INTEGER_CST
&& may_negate_without_overflow_p (tem))))
|| !INTEGRAL_TYPE_P (type))
return fold_build2_loc (loc, TREE_CODE (t), type,
negate_expr (tem), TREE_OPERAND (t, 1));
}
break;

5
gcc/testsuite/ChangeLog
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@ -1,3 +1,8 @@
2013-09-03 Richard Biener <rguenther@suse.de>
PR middle-end/57656
* gcc.dg/torture/pr57656.c: New testcase.
2013-09-03 Richard Biener <rguenther@suse.de>
PR middle-end/57287

13
gcc/testsuite/gcc.dg/torture/pr57656.c Normal file
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@ -0,0 +1,13 @@
/* { dg-do run } */
/* { dg-options "-fstrict-overflow" } */
int main (void)
{
int a = -1;
int b = __INT_MAX__;
int c = 2;
int t = 1 - ((a - b) / c); // t = 1 - ( __INT_MIN__ / 2 )
if (t != (1 - (-1 - __INT_MAX__) / 2))
__builtin_abort();
return 0;
}