Definition ror (x: nval) (amount: int) :=
  match x with
  | Nothing => Nothing
  | I m => I (Int.rol m amount)
  | All => All
  end.

Lemma ror_sound: forall v w x n, vagree v w (ror x n) -> vagree (Val.ror v (Vint n)) (Val.ror w (Vint n)) x.