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[Bug rtl-optimization/67786] 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: Wed, 30 Sep 2015 16:15:23 +0000
- Subject: [Bug rtl-optimization/67786] 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=67786
Bug ID: 67786
Summary: wrong code at -O2 and -O3 on x86_64-linux-gnu
Product: gcc
Version: 6.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: rtl-optimization
Assignee: unassigned at gcc dot gnu.org
Reporter: su at cs dot ucdavis.edu
Target Milestone: ---
The current gcc trunk miscompiles the following code on x86_64-linux-gnu at -O2
and -O3 in both 32-bit and 64-bit modes.
This is a regression from 5.2.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/6.0.0/lto-wrapper
Target: x86_64-pc-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 6.0.0 20150930 (experimental) [trunk revision 228291] (GCC)
$
$ gcc-trunk -Os small.c; ./a.out
15
$ gcc-5.2 -O2 small.c; ./a.out
15
$
$ gcc-trunk -O2 small.c; ./a.out
-32
$
$
-------------------------------------
int printf (const char *, ...);
int a, b = 10;
char c;
int
main ()
{
char d;
int e = 5;
for (a = 0; a; a--)
e = 0;
c = (b & 15) ^ e;
d = c > e ? c : c << e;
printf ("%d\n", d);
return 0;
}