Definition floatoflongu (x: aval) :=
  match x with
  | L i => F(Float.of_longu i)
  | _   => ntop1 x
  end.

(* Specifications: *)
Lemma floatoflongu_sound: forall v x w, vmatch v x -> Val.floatoflongu v = Some w -> vmatch w (floatoflongu x).