https://gcc.gnu.org/bugzilla/show_bug.cgi?id=69342
Bug ID: 69342
Summary: wrong code at -O1, -O2, -O3 (NOT -Os) on
x86-64-linux-gnu (in 32- and 64-bit modes)
Product: gcc
Version: 6.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: tree-optimization
Assignee: unassigned at gcc dot gnu.org
Reporter: chengniansun at gmail dot com
Target Milestone: ---
The following code is miscompiled by gcc trunk at -O1, -O2, -O3 (but not -Os)
in 32-bit and 64-bit modes.
$: 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 20160117 (experimental) [trunk revision 232481] (GCC)
$:
$: gcc-trunk small.c -O1 ; ./a.out
1
$: gcc-trunk small.c -O2 ; ./a.out
1
$: gcc-trunk small.c -O3 ; ./a.out
1
$: gcc-trunk small.c -O1 -m32 ; ./a.out
1
$: gcc-trunk small.c -O2 -m32 ; ./a.out
1
$: gcc-trunk small.c -O3 -m32 ; ./a.out
1
$: gcc-trunk small.c -Os -m32 ; ./a.out
4
$: gcc-trunk small.c -Os -m64 ; ./a.out
4
$: gcc-trunk small.c -O0 ; ./a.out
4
$:
$: cat small.c
int printf(const char*, ...);
static int a[40] = {7, 5, 3, 3, 0, 0, 3};
short b;
int c = 5;
int main() {
b = 0;
for (; b <= 3; b++)
if (a[b + 6] ^ (0 || c))
;
else
break;
printf("%d\n", b);
return 0;
}
$:
