Definition uintv (v: aval) : Z * Z :=
  match v with
  | I n => (Int.unsigned n, Int.unsigned n)
  | Uns _ n => if zlt n Int.zwordsize then (0, two_p n - 1) else (0, Int.max_unsigned)
  | _ => (0, Int.max_unsigned)
  end.

Lemma uintv_sound: forall n v, vmatch (Vint n) v -> fst (uintv v) <= Int.unsigned n <= snd (uintv v).