message: fixed boolean to bool
diff: a1: int = call @area x1 y1;
  a2: int = call @area x2 y2;
  res: int = sub a1 a2;
  - a1_bigger: boolean = gt a1 a2;
  + a1_bigger: bool = gt a1 a2;
  br a1_bigger .end .flip;
  .flip:
  neg1: int = const -1;
  