[Bug tree-optimization/121625] New: wrong code at -O{2,3} with "-fno-guess-branch-probability -fno-ssa-phiopt" on x86_64-linux-gnu

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

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=121625

            Bug ID: 121625
           Summary: wrong code at -O{2,3} with
                    "-fno-guess-branch-probability -fno-ssa-phiopt" 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/Tof3feYW6

Note:
- works: 15.2 and earlier
- fails: trunk

[604] % 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 20250820 (experimental) (GCC) 
[605] % 
[605] % gcctk -O3 small.c; ./a.out
0
[606] % gcctk -O3 -fno-guess-branch-probability -fno-ssa-phiopt small.c
[607] % ./a.out
1
[608] % cat small.c
int printf(const char *, ...);
int a, b;
int main() {
  long c = 4294967295;
  int d = ~(~c + ~(b & (2 + b)));
  long e = b - (b | c) || d;
  if (b < d)
    a = e;
  printf("%d\n", a);
  return 0;
}