Definition globals_separate {F V:Type} (ge: Genv.t F V) mu nu :=
    forall b1 b2 d, as_inj mu b1 = None ->
            as_inj nu b1 =Some(b2,d) ->
            isGlobalBlock ge b2 = false.

Lemma gsep_refl: forall {F V} mu (ge: Genv.t F V), globals_separate ge mu mu.