Section RENUMBER.
Variable f: PTree.t positive.
Hypothesis f_inj: forall x1 x2 y, f!x1 = Some y -> f!x2 = Some y -> x1 = x2.
End RENUMBER.
Definition pnum (f: function) := postorder (successors_map f) f.(fn_entrypoint).
Definition reach (f: function) (pc: node) := reachable (successors_map f) f.(fn_entrypoint) pc.

Lemma transf_function_at:
forall f pc i,
f.(fn_code)!pc = Some i ->
reach f pc ->
(transf_function f).(fn_code)!(renum_pc (pnum f) pc) = Some(renum_instr (pnum f) i).