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[Bug tree-optimization/61787] New: wrong code at -Os 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: Sat, 12 Jul 2014 05:12:57 +0000
- Subject: [Bug tree-optimization/61787] New: wrong code at -Os on x86_64-linux-gnu
- Auto-submitted: auto-generated
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=61787
Bug ID: 61787
Summary: wrong code at -Os on x86_64-linux-gnu
Product: gcc
Version: 4.10.0
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 (only)
-Os 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/4.10.0/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 4.10.0 20140711 (experimental) [trunk revision 212447] (GCC)
$
$ gcc-trunk -O1 small.c; a.out
$ gcc-trunk -O2 small.c; a.out
$ gcc-4.9 -Os small.c; a.out
$
$ gcc-trunk -Os small.c; a.out
Aborted (core dumped)
$
-------------------------
unsigned int a = 1;
int
fn1 ()
{
char b;
for (;;)
{
for (b = 0; b < 5; b++)
if (!a - (unsigned int) b)
return 0;
a = 0;
}
}
int
main ()
{
fn1 ();
if (a != 1)
__builtin_abort ();
return 0;
}