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re PR tree-optimization/63445 (request: make -Wstrict-overflow avoid a class of false positives)

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2014-10-09  Richard Biener  <rguenther@suse.de>

	PR tree-optimization/63445
	* tree-vrp.c (simplify_cond_using_ranges): Only warn about
	overflow for non-equality compares.

	* gcc.dg/Wstrict-overflow-26.c: New testcase.

From-SVN: r216028
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Richard Biener 2014-10-09 08:20:53 +00:00 • committed by Richard Biener
parent 9d55066c88
commit ee68591e69
4 changed files with 30 additions and 2 deletions
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6
gcc/ChangeLog
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@ -1,3 +1,9 @@
2014-10-09 Richard Biener <rguenther@suse.de>
PR tree-optimization/63445
* tree-vrp.c (simplify_cond_using_ranges): Only warn about
overflow for non-equality compares.
2014-10-09 Uros Bizjak <ubizjak@gmail.com>
PR rtl-optimization/57003

5
gcc/testsuite/ChangeLog
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@ -1,3 +1,8 @@
2014-10-09 Richard Biener <rguenther@suse.de>
PR tree-optimization/63445
* gcc.dg/Wstrict-overflow-26.c: New testcase.
2014-10-08 Pat Haugen <pthaugen@us.ibm.com>
* gcc.dg/vmx/3c-01a.c: Add default options from vmx.exp.

16
gcc/testsuite/gcc.dg/Wstrict-overflow-26.c Normal file
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@ -0,0 +1,16 @@
/* { dg-do compile } */
/* { dg-options "-O2 -Wstrict-overflow" } */
int
f (int i, int j)
{
unsigned int c = 0;
if (i < j)
{
unsigned int n = j - i;
unsigned int i;
for (i = 0; i < n; i++) /* { dg-bogus "signed overflow" } */
c++;
}
return c;
}

5
gcc/tree-vrp.c
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@ -9189,8 +9189,9 @@ simplify_cond_using_ranges (gimple stmt)
/* If the range overflowed and the user has asked for warnings
when strict overflow semantics were used to optimize code,
issue an appropriate warning. */
if ((is_negative_overflow_infinity (vr->min)
|| is_positive_overflow_infinity (vr->max))
if (cond_code != EQ_EXPR && cond_code != NE_EXPR
&& (is_negative_overflow_infinity (vr->min)
|| is_positive_overflow_infinity (vr->max))
&& issue_strict_overflow_warning (WARN_STRICT_OVERFLOW_CONDITIONAL))
{
location_t location;