[Bug tree-optimization/115927] New: wrong code at -O{2,3} with "-fno-tree-vrp" on x86_64-linux-gnu (nondeterministic behavior)

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

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=115927

            Bug ID: 115927
           Summary: wrong code at -O{2,3} with "-fno-tree-vrp" on
                    x86_64-linux-gnu (nondeterministic behavior)
           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 as it doesn't reproduce with 14.1 and
earlier. 

Compiler Explorer: https://godbolt.org/z/76naEWj7b

[582] % 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 20240714 (experimental) (GCC) 
[583] % 
[583] % gcctk -O2 small.c
[584] % ./a.out
0
[585] % gcctk -O2 -fno-tree-vrp small.c
[586] % ./a.out
[587] % ./a.out
[588] % ./a.out
0
[589] % ./a.out
0
[590] % cat small.c
int printf(const char *, ...);
int a, c, d;
long b;
char e;
int main() {
  d = 4 ^ a;
  e = (~(b & 5) & (0 || d) << c) % 4;
  if (e > 0)
    printf("%d\n", a);
  return 0;
}