[Bug tree-optimization/115152] New: wrong code at -O3 with "-fno-tree-fre -fno-tree-dominator-opts -fno-tree-loop-im" on x86_64-linux-gnu

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

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=115152

            Bug ID: 115152
           Summary: wrong code at -O3 with "-fno-tree-fre
                    -fno-tree-dominator-opts -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: ---

This appears to be a regression from 12.*, and affects 13.* and later. 

Compiler Explorer: https://godbolt.org/z/cvM1TYd7h


[598] % 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 20240516 (experimental) (GCC) 
[599] % 
[599] % gcctk -O3 small.c; ./a.out
[600] % 
[600] % gcctk -O3 -fno-tree-fre -fno-tree-dominator-opts -fno-tree-loop-im
small.c
[601] % ./a.out
Aborted
[602] % 
[602] % cat small.c
int a, b, c, d;
char e[1] = {1};
int main() {
  for (a = 0; a < 3; a++)
    for (b = 0; b < 2; b++)
      c = e[0] = e[0] ^ d;
  if (!c)
    __builtin_abort();
  return 0;
}