[Bug tree-optimization/123061] New: wrong code at -O3 with -ffinite-loops on x86_64-linux-gnu

[zhendong.su at inf dot ethz.ch via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=123061

            Bug ID: 123061
           Summary: wrong code at -O3 with -ffinite-loops 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/3T77KPjxb

Note:
- fails: 12.1 and later
- works: 11.4 and earlier

[673] % 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 20251208 (experimental) (GCC) 
[674] % 
[674] % gcctk -O3 small.c; ./a.out
[675] % 
[675] % gcctk -O3 -ffinite-loops small.c
[676] % ./a.out
Floating point exception
[677] % 
[677] % cat small.c
int a, b, c, d;
int e(int f) {
  if (f)
    goto L;
  while (1) {
    b = 1;
  L:
    d -= b;
    if (d) {
      if (2 / c )
        goto L;
      return 0;
    }
    c = f;
  }
}
int main() {
  int g = 3;
  do {
    e(g);
  } while (a);
  return 0;
}