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[Bug tree-optimization/71518] New: wrong code at -O3 on x86_64-linux-gnu in 64-bit mode (not in 32-bit mode)
- 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, 13 Jun 2016 08:04:30 +0000
- Subject: [Bug tree-optimization/71518] New: wrong code at -O3 on x86_64-linux-gnu in 64-bit mode (not in 32-bit mode)
- Auto-submitted: auto-generated
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=71518
Bug ID: 71518
Summary: wrong code at -O3 on x86_64-linux-gnu in 64-bit mode
(not in 32-bit mode)
Product: gcc
Version: 7.0
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: ---
The current gcc trunk and 6.1.x miscompile the following code on
x86_64-linux-gnu at -O3 in the 64-bit mode (but not in the 32-bit mode).
This is a regression from 5.4.x, and goes away with -fno-tree-vectorize.
$ 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 20160612 (experimental) [trunk revision 237336] (GCC)
$
$ gcc-trunk -m32 -O3 small.c; ./a.out
$ gcc-trunk -m64 -O2 small.c; ./a.out
$ gcc-5.4 -O3 small.c; ./a.out
$
$ gcc-trunk -m64 -O3 small.c
$ ./a.out
Segmentation fault (core dumped)
$
$ gcc-6.1 -m64 -O3 small.c
$ ./a.out
Segmentation fault (core dumped)
$
--------------------------------
int a, *b[9], c, d, e;
static int
fn1 ()
{
for (c = 6; c >= 0; c--)
for (d = 0; d < 2; d++)
{
b[d * 2 + c] = 0;
e = a > 1 ? : 0;
if (e == 2)
return 0;
}
return 0;
}
int
main ()
{
fn1 ();
return 0;
}