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[Bug tree-optimization/78856] New: wrong code at -O3 on x86_64-linux-gnu (in both 32-bit and 64-bit modes)
- From: "su at cs dot ucdavis.edu" <gcc-bugzilla at gcc dot gnu dot org>
- To: gcc-bugs at gcc dot gnu dot org
- Date: Mon, 19 Dec 2016 07:52:13 +0000
- Subject: [Bug tree-optimization/78856] New: wrong code at -O3 on x86_64-linux-gnu (in both 32-bit and 64-bit modes)
- Auto-submitted: auto-generated
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=78856
Bug ID: 78856
Summary: wrong code at -O3 on x86_64-linux-gnu (in both 32-bit
and 64-bit modes)
Product: gcc
Version: unknown
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: tree-optimization
Assignee: unassigned at gcc dot gnu.org
Reporter: su at cs dot ucdavis.edu
Target Milestone: ---
It affects 6.x and later, and is a regression from 5.x.
$ gcc-trunk -v
Using built-in specs.
COLLECT_GCC=gcc-trunk
COLLECT_LTO_WRAPPER=/usr/local/gcc-trunk/libexec/gcc/x86_64-pc-linux-gnu/7.0.0/lto-wrapper
Target: x86_64-pc-linux-gnu
Configured with: ../gcc-source-trunk/configure --enable-languages=c,c++,lto
--prefix=/usr/local/gcc-trunk --disable-bootstrap
Thread model: posix
gcc version 7.0.0 20161218 (experimental) [trunk revision 243783] (GCC)
$
$ gcc-trunk -O2 small.c; ./a.out
$ gcc-5.4 -O3 small.c; ./a.out
$
$ gcc-trunk -O3 small.c
$ timeout -s 9 5 ./a.out
Killed
$
--------------------------------------------
int a, b, c, d, e, f[3];
int main()
{
while (d)
while (1)
;
int g = 0, h, i = 0;
for (; g < 21; g += 9)
{
int j = 1;
for (h = 0; h < 3; h++)
f[h] = 1;
for (; j < 10; j++) {
d = i && (b ? 0 : c);
i = 1;
if (g)
a = e;
}
}
return 0;
}