[Bug tree-optimization/60770] disappearing clobbers

[glisse at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=60770

--- Comment #1 from Marc Glisse <glisse at gcc dot gnu.org> ---
int f(int n){
  int*p;
  {
    int q=n;
    p=&q;
  }
  return *p;
}

Here CCP turns:

  q = n_2(D);
  p_4 = &q;
  q ={v} {CLOBBER};
  _6 = *p_4;

into:

  q_5 = n_2(D);
  _6 = q_5;

I guess relying on clobbers in the middle-end for warnings is a bit
optimistic...