(** * Soundness of operations over value numberings *)
Remark wf_equation_incr:
forall next1 next2 e,
wf_equation next1 e -> Ple next1 next2 -> wf_equation next2 e.
(** Extensionality with respect to valuations. *)
Definition valu_agree (valu1 valu2: valuation) (upto: valnum) :=
forall v, Plt v upto -> valu2 v = valu1 v.
Section EXTEN.
Variable valu1: valuation.
Variable upto: valnum.
Variable valu2: valuation.
Hypothesis AGREE: valu_agree valu1 valu2 upto.
Variable ge: genv.
Variable sp: val.
Variable rs: regset.
Variable m: mem.

Lemma equation_holds_exten:
forall e,
equation_holds valu1 ge sp m e ->
wf_equation upto e ->
equation_holds valu2 ge sp m e.