Lemma semax_while_peel: forall {CS: compspecs} {Espec: OracleKind} Inv Delta P expr body R, @semax CS Espec Delta P (Ssequence (Sifthenelse expr Sskip Sbreak) body) (loop1_ret_assert Inv R) -> @semax CS Espec Delta Inv (Swhile expr body) R -> @semax CS Espec Delta P (Swhile expr body) R.