Ltac hered :=
  match goal with
    H : ?P ?x |- ?P ?y => revert H
  end;
  match goal with
    |- ?P ?x -> ?P ?y =>
    cut (hereditary age P);
    [ let h := fresh "h" in intros h; apply h; auto | ]
  end.Ltac agejoinhyp :=
  match goal with
    H : sepalg.join _ _ ?m, A : age ?m _ |- _ =>
    pose proof age1_join2 _ H A; clear H
  end.Ltac agehyps :=
  match goal with
    H : age ?x ?y, HH : ?P ?x |- _ =>
    cut (P y);
    [ clear HH; intros HH
    | hered;
      try apply pred_hered;
      try apply predicates_hered.exactly_obligation_1]
  end.

Lemma jstep_age_sim {C} {csem : @semantics.CoreSemantics C mem} {c c' jm1 jm2 jm1'} : age jm1 jm2 -> jstep csem c jm1 c' jm1' -> level jm2 <> O -> exists jm2', age jm1' jm2' /\ jstep csem c jm2 c' jm2'.