C2 can not merge trivial Ifs due to CastII

C2 can not apply Split If for the following trivial case. After a quick investigation, CastII generated by Parse::sharpen_type_after_if prevents it from being optimized out, because PhiNode::Identity can not find existing Cmp if we don't allow cast(unique_input(n,false/*uncast*/))

  public static void test5(int a, int b){
 
    if( b!=0) {
      int_field = 35;
    } else {
      int_field =222;
    }

    if( b!=0) {
      int_field = 35;
    } else {
      int_field =222;
    }
  }