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[Bug tree-optimization/60196] New: Incorrect compilation with -fwrapv and -ftree-vectorize
- From: "dpb at corrigendum dot ru" <gcc-bugzilla at gcc dot gnu dot org>
- To: gcc-bugs at gcc dot gnu dot org
- Date: Fri, 14 Feb 2014 15:21:57 +0000
- Subject: [Bug tree-optimization/60196] New: Incorrect compilation with -fwrapv and -ftree-vectorize
- Auto-submitted: auto-generated
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=60196
Bug ID: 60196
Summary: Incorrect compilation with -fwrapv and
-ftree-vectorize
Product: gcc
Version: 4.8.2
Status: UNCONFIRMED
Severity: major
Priority: P3
Component: tree-optimization
Assignee: unassigned at gcc dot gnu.org
Reporter: dpb at corrigendum dot ru
Created attachment 32135
--> http://gcc.gnu.org/bugzilla/attachment.cgi?id=32135&action=edit
Preprocessed source for the reproducer
This program should print 36 (preprocessed source attached):
#include <stdio.h>
static int foo(const short * a, int len)
{
int x;
int x1 = 0;
for( x = 0; x < len; x++ )
x1 += x * a[x];
return x1;
}
int main()
{
short stuff[9] = {1,1,1,1,1,1,1,1,1};
printf("%d\n", foo(stuff, 9));
return 0;
}
However, if compiled with -O1 -fwrapv -ftree-vectorize, it prints 16 instead.
Omitting any of those flags gives the correct result.
I can reproduce this on 4.8.2 and 4.8 branch head. It doesn't reproduce on
trunk, though. (All three built from vanilla source.) Target is
x86_64-unknown-linux-gnu.
I also tested it on a bunch of Ubuntu's prebuilt GCC versions. It reproduces on
4.6.4, 4.7.3, 4.8.1, but not on 4.4.7.