Definition longuoffloat (x: aval) :=
  match x with
  | F f =>
      match Float.to_longu f with
      | Some i => L i
      | None => if va_strict tt then Vbot else ntop
      end
  | _ => ntop1 x
  end.

Lemma longuoffloat_sound: forall v x w, vmatch v x -> Val.longuoffloat v = Some w -> vmatch w (longuoffloat x).