(* The following two lemmas is not now used. but after deep embedded hoare logic (SL_as_Logic) is ported, the frame does not need to be quantified in the semantic definition of semax. Then, these two lemmas can replace the other two afterwards. *)

Lemma assert_safe_except_0':
forall {Espec: OracleKind} gx vx tx PP1 PP2 rho (P: environ -> pred rmap) k,
PP1 && (P rho) && PP2 >=>
assert_safe Espec gx vx tx k rho =
PP1 && ((|> FF || P rho)) && PP2 >=>
assert_safe Espec gx vx tx k rho.