https://gcc.gnu.org/bugzilla/show_bug.cgi?id=109778
Bug ID: 109778
Summary: Wrong code at -O3 on x86_64-linux-gnu since GCC-12.2
Product: gcc
Version: 14.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c
Assignee: unassigned at gcc dot gnu.org
Reporter: shaohua.li at inf dot ethz.ch
Target Milestone: ---
gcc trunk at -O3 emits wrong code. This seems to be a bug since gcc-12.2
Compiler explorer: https://godbolt.org/z/E5aqnMK6Y
$ cat a.c
int printf(const char *, ...);
int a, b, c, d;
int *e = &c;
unsigned f(unsigned char g) {
g = 1 | g << 1;
g = g >> 4 | g << 4;
return g;
}
void h(unsigned g) { *e = 8 > f(g + 86) - 86; }
int main() {
d = a && b;
h(d + 4);
printf("%d\n", c);
}
$
$ gcc-tk -O0 a.c && ./a.out
1
$ gcc-tk -O3 a.c && ./a.out
0
$
$ gcc-tk -v
Using built-in specs.
COLLECT_GCC=gcc-tk
COLLECT_LTO_WRAPPER=/zdata/shaoli/compilers/ccbuilder-compilers/gcc-b7fe38c14e5f1bc32950c7b2ffc8537c7c381af4/libexec/gcc/x86_64-pc-linux-gnu/14.0.0/lto-wrapper
Target: x86_64-pc-linux-gnu
Configured with: ../configure --disable-multilib --disable-bootstrap
--enable-languages=c,c++
--prefix=/zdata/shaoli/compilers/ccbuilder-compilers/gcc-b7fe38c14e5f1bc32950c7b2ffc8537c7c381af4
Thread model: posix
Supported LTO compression algorithms: zlib
gcc version 14.0.0 20230506 (experimental) (GCC)
$
