Ltac simpl_compb :=
  match goal with
  | |- context [if Z.ltb ?x ?y then _ else _] =>
         first [ rewrite (if_trueb (Z.ltb x y)) by (apply Z.ltb_lt; omega)
               | rewrite (if_falseb (Z.ltb x y)) by (apply Z.ltb_ge; omega)]
  end.Axiom tree_inb_true_iff: forall x (t: tree val), tree_inb x t = true <-> key_store_ t x.Axiom tree_inb_false_iff: forall x (t: tree val), tree_inb x t = false <-> ~ key_store_ t x.

Lemma body_subscr: semax_body Vprog Gprog f_subscr subscr_spec.