[Bug tree-optimization/116405] New: wrong code at -O{2,3} with "-fno-ssa-phiopt -fno-tree-dce" on x86_64-linux-gnu

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

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=116405

            Bug ID: 116405
           Summary: wrong code at -O{2,3} with "-fno-ssa-phiopt
                    -fno-tree-dce" 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 recent regression as it doesn't reproduce with 14.* and
earlier. 

Compiler Explorer: https://godbolt.org/z/Tnzx45e4c


[615] % 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 20240818 (experimental) (GCC) 
[616] % 
[616] % gcctk -O2 small.c; ./a.out
0
[617] % gcctk -O2 -fno-ssa-phiopt -fno-tree-dce small.c
[618] % ./a.out
0
Floating point exception
[619] % 
[619] % cat small.c
int printf(const char *, ...);
int a, b = 2, c = 1;
unsigned d, e;
int main() {
 L:
  a = -1 / c;
  d = ~(b && (c && ~e) & b);
  printf("0\n");
  c = 0;
  if (d < -1)
    goto L;
  return 0;
}