[Bug tree-optimization/99943] New: wrong code at -Os

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

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=99943

            Bug ID: 99943
           Summary: wrong code at -Os
           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: ---

[538] % 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/11.0.1/lto-wrapper
Target: x86_64-pc-linux-gnu
Configured with: ../gcc-trunk/configure --disable-bootstrap
--prefix=/local/suz-local/software/local/gcc-trunk --enable-languages=c,c++
--disable-werror --enable-multilib --with-system-zlib
Thread model: posix
Supported LTO compression algorithms: zlib
gcc version 11.0.1 20210406 (experimental) [master revision
62321ab477e:8aa4f7b4faf:d48f87d5c1927b1bf2009af3251fe8757e823713] (GCC) 
[539] % 
[539] % gcctk -O1 small.c; ./a.out
[540] % 
[540] % gcctk -Os small.c
[541] % ./a.out
Aborted
[542] % 
[542] % cat small.c
char a;
int b, c[8];
int main() {
  for (; a < 8; a++) {
    for (b = 0; b < 8; b++)
      c[a] = 1;
    c[a] = 0;
  }
  if (c[0] != 0)
    __builtin_abort ();
  return 0;
}