[Bug tree-optimization/101501] [11/12 Regression] wrong code at -O3 on x86_64-linux-gnu

[glisse at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=101501

--- Comment #2 from Marc Glisse <glisse at gcc dot gnu.org> ---
unsigned char a = 55;
int main() {
  unsigned char c;
d:
  c = a-- * 52;
  if (c)
    goto d;
  __builtin_printf("%d\n", a);
}


outputs 40 at -O3 instead of 255, and already fails with gcc-8. Cunroll seems
confused about the number of iterations of this loop.