(** Commutation with [find_label]. *)

Lemma remove_unused_labels_cons:
forall bto i c,
remove_unused_labels bto (i :: c) =
match i with
| Llabel lbl =>
if Labelset.mem lbl bto then i :: remove_unused_labels bto c else remove_unused_labels bto c
| _ =>
i :: remove_unused_labels bto c
end.