https://gcc.gnu.org/bugzilla/show_bug.cgi?id=121577
Bug ID: 121577
Summary: wrong code at -O{s,2,3} with "-fno-tree-pre
-fno-code-hoisting -fno-tree-fre
-fno-tree-dominator-opts -fno-gcse -fno-tree-loop-im"
on x86_64-linux-gnu
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/ee1vhKGMv
Note:
- works: 10.5 and earlier
- fails: 11.1 and later
- still fails with -fno-tree-slsr and -fno-ivopts
- does seem to require disabling several flags
[777] % 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 20250817 (experimental) (GCC)
[778] %
[778] % gcctk -O3 -fno-tree-pre -fno-code-hoisting -fno-tree-fre
-fno-tree-dominator-opts -fno-gcse -fno-tree-loop-im small.c
[779] % ./a.out
Aborted
[780] % cat small.c
int a[] = {-3, 2, -2}, b, d, e;
void f(int g, int h) {
int i = 12 / h;
do {
if (5 / i)
g = 0;
e = 5 / i - 6;
} while (2 / e);
b = 2 - 5 % i;
int j[] = {b, 2, g};
for (int c = 0; c < 3; c++)
if (j[c] != a[c])
__builtin_abort();
}
int main() {
d = 2;
f(-2, d);
return 0;
}
