Corollary find_label_translated:
  forall f i c' lbl c,
  incl (i :: c') (fn_code f) ->
  find_label lbl (fn_code f) = Some c ->
  instr_branches_to i lbl ->
  find_label lbl (fn_code (transf_function f)) =
     Some (remove_unused_labels (labels_branched_to (fn_code f)) c).

Lemma find_label_incl: forall lbl c c', find_label lbl c = Some c' -> incl c' c.