https://gcc.gnu.org/bugzilla/show_bug.cgi?id=120521
Bug ID: 120521
Summary: wrong code at -O3 with "-fno-tree-fre" on
x86_64-linux-gnu (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: ---
Compiler Explorer: https://godbolt.org/z/8W3Ec8TzK
It appears to be a regression from 13.*, and affects 14.* and later.
[542] % gcctk -v
Using built-in specs.
COLLECT_GCC=gcctk
COLLECT_LTO_WRAPPER=/local/home/suz/suz-local/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 20250603 (experimental) (GCC)
[543] %
[543] % gcctk -O3 small.c; ./a.out
[544] %
[544] % gcctk -O3 -fno-tree-fre small.c
[545] % timeout -s 9 10 ./a.out
Killed
[546] %
[546] % cat small.c
int a, b, c = -2147483647;
int main() {
int d = -2147483646, e = -2147483645, f = 0;
goto g;
h:
b -= 429496729;
if (d + 858993461 >= b) {
if (f + 2147483644 <= 0) {
if (b - f >= 0)
goto h;
b = -1;
}
goto i;
}
j:
f -= 715827882;
if (f - c >= 1431655765) {
b = -e - 2147483647;
if (b)
goto h;
goto i;
}
goto h;
i:
a = -999 * b - 2147483647;
if (a)
return 0;
g:
goto j;
return 0;
}
