This is the mail archive of the
gcc-bugs@gcc.gnu.org
mailing list for the GCC project.
[Bug tree-optimization/64682] New: wrong code at -O2 and -O3 on x86_64-linux-gnu
- 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: Tue, 20 Jan 2015 07:14:20 +0000
- Subject: [Bug tree-optimization/64682] New: wrong code at -O2 and -O3 on x86_64-linux-gnu
- Auto-submitted: auto-generated
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=64682
Bug ID: 64682
Summary: wrong code at -O2 and -O3 on x86_64-linux-gnu
Product: gcc
Version: 5.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: tree-optimization
Assignee: unassigned at gcc dot gnu.org
Reporter: su at cs dot ucdavis.edu
The current gcc trunk miscompiles the following code on x86_64-linux at -O2 and
-O3 in both 32-bit and 64-bit modes.
This is a regression from 4.9.x.
$ gcc-trunk -v
Using built-in specs.
COLLECT_GCC=gcc-trunk
COLLECT_LTO_WRAPPER=/usr/local/gcc-trunk/libexec/gcc/x86_64-unknown-linux-gnu/5.0.0/lto-wrapper
Target: x86_64-unknown-linux-gnu
Configured with: ../gcc-trunk/configure --prefix=/usr/local/gcc-trunk
--enable-languages=c,c++ --disable-werror --enable-multilib
Thread model: posix
gcc version 5.0.0 20150119 (experimental) [trunk revision 219832] (GCC)
$
$ gcc-trunk -Os small.c; a.out
5
$ gcc-4.9 -O2 small.c; a.out
5
$
$ gcc-trunk -O2 small.c; a.out
1
$
-----------------------------------
int printf (const char *, ...);
int a, b = 1;
int
main ()
{
int i;
for (i = 0; i < 56; i++)
for (; a; a--)
;
int *c = &b;
if (*c)
*c = 1 % (unsigned int) *c | 5;
printf ("%d\n", b);
return 0;
}