Definition slot_valid (sl: slot) (ofs: Z) (ty: typ): bool :=
  match sl with
  | Local => zle 0 ofs
  | Outgoing => zle 0 ofs
  | Incoming => In_dec Loc.eq (S Incoming ofs ty) (regs_of_rpairs (loc_parameters funct.(fn_sig)))
  end
  && Zdivide_dec (typealign ty) ofs (typealign_pos ty).Definition slot_writable (sl: slot) : bool :=
  match sl with
  | Local => true
  | Outgoing => true
  | Incoming => false
  end.Definition loc_valid (l: loc) : bool :=
  match l with
  | R r => true
  | S Local ofs ty => slot_valid Local ofs ty
  | S _ _ _ => false
  end.Fixpoint wt_builtin_res (ty: typ) (res: builtin_res mreg) : bool :=
  match res with
  | BR r => subtype ty (mreg_type r)
  | BR_none => true
  | BR_splitlong hi lo => wt_builtin_res Tint hi && wt_builtin_res Tint lo
  end.Definition wt_instr (i: instruction) : bool :=
  match i with
  | Lgetstack sl ofs ty r =>
      subtype ty (mreg_type r) && slot_valid sl ofs ty
  | Lsetstack r sl ofs ty =>
      slot_valid sl ofs ty && slot_writable sl
  | Lop op args res =>
      match is_move_operation op args with
      | Some arg =>
          subtype (mreg_type arg) (mreg_type res)
      | None =>
          let (targs, tres) := type_of_operation op in
          subtype tres (mreg_type res)
      end
  | Lload chunk addr args dst =>
      subtype (type_of_chunk chunk) (mreg_type dst)
  | Ltailcall sg ros =>
      zeq (size_arguments sg) 0
  | Lbuiltin ef args res =>
      wt_builtin_res (proj_sig_res (ef_sig ef)) res
      && forallb loc_valid (params_of_builtin_args args)
  | _ =>
      true
  end.Definition wt_code (f: function) (c: code) : bool :=
  forallb (wt_instr f) c.Definition wt_function (f: function) : bool :=
  wt_code f f.(fn_code).(** Typing the run-time state. *)

Definition wt_locset (ls: locset) : Prop :=
  forall l, Val.has_type (ls l) (Loc.type l).

Lemma wt_return_regs: forall caller callee, wt_locset caller -> wt_locset callee -> wt_locset (return_regs caller callee).