https://gcc.gnu.org/bugzilla/show_bug.cgi?id=110732
Bug ID: 110732
Summary: Wrong code at -Os on x86_64-linux-gnu (recent
regression)
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: ---
This looks like a recent regression. gcc at -Os produces the wrong code.
Compiler explorer: https://godbolt.org/z/WWdxfzPrc
$ cat a.c
int printf(const char *, ...);
int a;
char c[] = {0, 0, -4L};
char d, e;
int main() {
int f;
int *g = &a;
*g = 1;
for (; e <= 2; e++)
for (;;) {
{
{
int b = c[e];
f = b < 0 ? b : b >> 6;
}
d = f && a;
}
break;
}
printf("%d\n", d);
}
$
$ gcc-tk -O0 a.c && ./a.out
1
$ gcc-tk -Os a.c && ./a.out
-1
$
$ gcc-tk -v
Using built-in specs.
COLLECT_GCC=gcc-tk
COLLECT_LTO_WRAPPER=/zdata/shaoli/compilers/ccbuilder-compilers/gcc-322d17ae51ea0137167424e0018d7fa355948f9f/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-322d17ae51ea0137167424e0018d7fa355948f9f
Thread model: posix
Supported LTO compression algorithms: zlib
gcc version 14.0.0 20230711 (experimental) (GCC)
$
