Definition ge (x y: t) : Prop :=
    NE.ge (fst x) (fst y) /\
    (forall ge sp b ofs, nlive ge sp (snd y) b ofs -> nlive ge sp (snd x) b ofs).

(* Specifications: *)
Lemma ge_refl: forall x y, eq x y -> ge x y.
Lemma ge_trans: forall x y z, ge x y -> ge y z -> ge x z.