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 rhs_eval_to_exten:
forall r v,
rhs_eval_to valu1 ge sp m r v ->
(forall v, In v (valnums_rhs r) -> Plt v upto) ->
rhs_eval_to valu2 ge sp m r v.