https://gcc.gnu.org/bugzilla/show_bug.cgi?id=121619
Bug ID: 121619
Summary: wrong code at -O{s,2,3} with "-fno-gcse -fno-tree-ter
-fno-guess-branch-probability -fno-forward-propagate"
on x86_64-linux-gnu (the generated code hangs)
Product: gcc
Version: unknown
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: tree-optimization
Assignee: unassigned at gcc dot gnu.org
Reporter: zhendong.su at inf dot ethz.ch
Target Milestone: ---
It's a recent regression as it doesn't fail with the latest Compiler Explorer
build.
[516] % gcctk -v
Using built-in specs.
COLLECT_GCC=gcctk
COLLECT_LTO_WRAPPER=/local/home/suz/software/local/gcc-trunk/bin/../libexec/gcc/x86_64-pc-linux-gnu/16.0.0/lto-wrapper
Target: x86_64-pc-linux-gnu
Configured with: ../gcc-trunk/configure --disable-bootstrap
--enable-checking=yes --prefix=/local/suz-local/software/local/gcc-trunk
--enable-sanitizers --enable-languages=c,c++ --disable-werror --enable-multilib
Thread model: posix
Supported LTO compression algorithms: zlib
gcc version 16.0.0 20250820 (experimental) (GCC)
[517] %
[517] % gcctk -O3 small.c; ./a.out
[518] %
[518] % gcctk -O3 -fno-gcse -fno-tree-ter -fno-guess-branch-probability
-fno-forward-propagate small.c
[519] % timeout -s 9 5 ./a.out
Killed
[520] % cat small.c
int printf(const char *, ...);
long a, c, d;
char b;
int main() {
f : {
short g = 100;
int h = 1;
while (1) {
char i = 0;
if (a)
i = h = -b;
short j = g;
c = h ^ g;
g = ~(-h / c + 1);
if (b > 6) {
a = g && -1;
goto f;
}
if (j < 100)
printf("%ld\n", d);
if (g - 1)
break;
b = i;
}
int k = 2L % g;
if (k)
goto f;
}
return 0;
}
