proposition: Lemma make_header_tag_prep32: forall z, 0 <= z < two_p (4 * 8) -> Int.and (Int.repr z) (Int.repr 255) = Int.sub (Int.repr z) (Int.mul (Int.repr (z / two_p 8)) (Int.repr (two_p 8))).
proof: Proof. intros. replace (Int.repr 255) with (Int.sub (Int.repr 256) Int.one) by now vm_compute. rewrite <- (Int.modu_and _ _ (Int.repr 8)) by now vm_compute. rewrite Int.modu_divu by (vm_compute; intro S; inversion S). rewrite (Int.divu_pow2 _ _ (Int.repr 8)) by now vm_compute. rewrite (Int.mul_pow2 _ _ (Int.repr 8)) by now vm_compute. rewrite Int.shru_div_two_p, !Int.unsigned_repr; [| rep_lia | ]. - rewrite Int.shl_mul_two_p, Int.unsigned_repr by rep_lia. easy. - simpl Z.mul in H. unfold Int.max_unsigned, Int.modulus. unfold Int.wordsize, Wordsize_32.wordsize. rewrite two_power_nat_two_p. simpl Z.of_nat. lia. Qed.
imports: Coq.ZArith.ZArith Coq.Program.Basics Coq.micromega.Lia compcert.lib.Integers compcert.common.Values VST.veric.base VST.veric.Clight_lemmas VST.veric.val_lemmas VST.veric.shares VST.msl.seplog VST.msl.shares VST.zlist.sublist VST.floyd.coqlib3 VST.floyd.functional_base VST.floyd.data_at_rec_lemmas VST.zlist.list_solver CertiGraph.lib.EquivDec_ext CertiGraph.lib.List_ext CertiGraph.graph.graph_model CertiGraph.graph.graph_gen