[Bug tree-optimization/117192] New: wrong code at -O3 with "-fno-unswitch-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=117192

            Bug ID: 117192
           Summary: wrong code at -O3 with "-fno-unswitch-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: ---

It appears to be a very recent regression as it doesn't reproduce with the GCC
build from Compiler Explorer.

[522] % 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/15.0.0/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 15.0.0 20241016 (experimental) (GCC) 
[523] % 
[523] % gcctk -O3 -fno-unswitch-loops small.c
[524] % ./a.out
Aborted
[525] % 
[525] % cat small.c
int a, b, c, d;
int main() {
  int e[6];
  for (d = 0; d < 6; d++)
    if (!c)
      e[d] = 0;
  for (; b < 6; b++)
    a = e[b];
  if (a != 0)
    __builtin_abort();
  return 0;
}