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 ltu_repr: forall i j,
(0 <= i <= Int.max_unsigned ->
0 <= j <= Int.max_unsigned ->
Int.ltu (Int.repr i) (Int.repr j) = true -> i<j)%Z.