[Bug tree-optimization/111838] New: wrong code at -O3 on x86_64-linux-gnu

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

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=111838

            Bug ID: 111838
           Summary: wrong code at -O3 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: ---

It appears to be a recent regression.

Compiler Explorer: https://godbolt.org/z/Mx76x5h5K


[614] % gcctk -v
Using built-in specs.
COLLECT_GCC=gcctk
COLLECT_LTO_WRAPPER=/local/suz-local/software/local/gcc-trunk/libexec/gcc/x86_64-pc-linux-gnu/14.0.0/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 14.0.0 20231016 (experimental) (GCC) 
[615] % 
[615] % gcctk -O2 small.c; ./a.out
[616] % 
[616] % gcctk -O3 small.c; ./a.out
small.c: In function ‘main’:
small.c:6:17: warning: iteration 4 invokes undefined behavior
[-Waggressive-loop-optimizations]
    6 |       if (e ? a % e : 0)
      |               ~~^~~
small.c:5:26: note: within this loop
    5 |     for (char e = -17; e < 1; e += 5) {
      |                        ~~^~~
Floating point exception
[617] % 
[617] % cat small.c
int a, b, c;
volatile char d;
int main() {
  for (; b < 1; b++)
    for (char e = -17; e < 1; e += 5) {
      if (e ? a % e : 0)
        d;
      for (c = 0; c < 1; c++)
        ;
    }
  return 0;
}