Fixpoint set_params' (vl: list val) (il: list ident) (te: Cminor.env) : Cminor.env :=
match il, vl with
| i1 :: is, v1 :: vs => set_params' vs is (PTree.set i1 v1 te)
| i1 :: is, nil => set_params' nil is (PTree.set i1 Vundef te)
| _, _ => te
end.

Lemma set_params'_inside:
forall id il vl te1 te2,
In id il ->
(set_params' vl il te1)!id = (set_params' vl il te2)!id.