Hint Rewrite proj_sumbool_is_true using (solve [auto 3]) : norm.
Hint Rewrite proj_sumbool_is_false using (solve [auto 3]) : norm.

(* Specifications: *)
Lemma ptrofs_to_int_repr:
forall x, (Ptrofs.to_int (Ptrofs.repr x)) = Int.repr x.