Definition singleoflongu (x: aval) :=
  match x with
  | L i => FS(Float32.of_longu i)
  | _   => ntop1 x
  end.

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