[Bug tree-optimization/106171] New: wrong code at -O1 and above on x86_64-linux-gnu

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

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=106171

            Bug ID: 106171
           Summary: wrong code at -O1 and above 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 quite long-latent, and affects all versions 7.* and later. 

[560] % 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/13.0.0/lto-wrapper
Target: x86_64-pc-linux-gnu
Configured with: ../gcc-trunk/configure --disable-bootstrap
--prefix=/local/suz-local/software/local/gcc-trunk --enable-sanitizers
--enable-languages=c,c++ --disable-werror --enable-multilib --with-system-zlib
Thread model: posix
Supported LTO compression algorithms: zlib
gcc version 13.0.0 20220703 (experimental) [master r13-1411-ga26f3eb2683] (GCC) 
[561] % 
[561] % gcctk -O0 small.c; ./a.out
1
[562] % gcctk -O1 small.c; ./a.out
0
[563] % gcctk -Os small.c; ./a.out
-2089837456
[564] % gcctk -O2 small.c; ./a.out
0
[565] % gcctk -O3 small.c; ./a.out
0
[566] % 
[566] % cat small.c
int printf(const char *, ...);
int a, b;
int c() {
  int d = 0;
  for (; d < 2; d++) {
    int e[2];
    for (; b < 2; b++)
      e[b] = 1;
    if (d)
      return e[0];
  }
  return 0;
}
int main() {
  a = c();
  printf("%d\n", a);
  return 0;
}