[Bug tree-optimization/58978] [4.9 Regression] ICE: Segmentation fault

[mpolacek at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=58978

--- Comment #2 from Marek Polacek <mpolacek at gcc dot gnu.org> ---
Here, single_imm_use can set the stmt to NULL:

  /* If there aren't any uses whatsoever, we're done.  */
  if (ptr == ptr->next)
    {   
    return_false:
      *use_p = NULL_USE_OPERAND_P;
      *stmt = NULL;

and then we're calling gimple_code on that NULL stmt:
  if (gimple_code (use_stmt) != GIMPLE_COND