Definition all_assertions_computable  :=
  forall (Espec: OracleKind) psi tx vx (Q: assert), 
     exists k,  assert_safe Espec psi tx vx k = Q.

Lemma semax_frame {CS: compspecs} {Espec: OracleKind}: forall Delta P s R F, closed_wrt_modvars s F -> semax Espec Delta P s R -> semax Espec Delta (fun rho => P rho * F rho) s (frame_ret_assert R F).