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 gpo: forall p v m l, forall_rpair (fun r => Loc.diff l (R r)) p -> setpair p v m l = m l.