Hint Rewrite offset_offset_val: norm.
Hint Rewrite add_repr add64_repr ptrofs_add_repr : norm.
Hint Rewrite mul_repr mul64_repr ptrofs_mul_repr : norm.
Hint Rewrite sub_repr sub64_repr ptrofs_sub_repr : norm.
Hint Rewrite and_repr and64_repr : norm.
Hint Rewrite or_repr or64_repr : norm.
Hint Rewrite neg_repr neg64_repr : norm.

Lemma int_add_assoc1:
forall z i j, Int.add (Int.add z (Int.repr i)) (Int.repr j) = Int.add z (Int.repr (i+j)).