Definition getpair (p: rpair loc) (m: t) : val :=
    match p with
    | One l => m l
    | Twolong l1 l2 => Val.longofwords (m l1) (m l2)
    end.Definition setpair (p: rpair mreg) (v: val) (m: t) : t :=
    match p with
    | One r => set (R r) v m
    | Twolong hi lo => set (R lo) (Val.loword  v) (set (R hi) (Val.hiword v) m)
    end.

Lemma getpair_exten: forall p ls1 ls2, (forall l, In l (regs_of_rpair p) -> ls2 l = ls1 l) -> getpair p ls2 = getpair p ls1.