(** The general shape of activation records is as follows,
  from bottom (lowest offsets) to top:
- Space for outgoing arguments to function calls.
- Back link to parent frame
- Saved values of integer callee-save registers used by the function.
- Saved values of float callee-save registers used by the function.
- Local stack slots.
- Space for the stack-allocated data declared in Cminor
- Return address.
*)

Definition fe_ofs_arg := 0.Definition make_env (b: bounds) : frame_env :=
  let w := if Archi.ptr64 then 8 else 4 in
  let olink := align (4 * b.(bound_outgoing)) w in  (* back link *)
  let ocs := olink + w in                           (* callee-saves *)
  let ol :=  align (size_callee_save_area b ocs) 8 in (* locals *)
  let ostkdata := align (ol + 4 * b.(bound_local)) 8 in (* stack data *)
  let oretaddr := align (ostkdata + b.(bound_stack_data)) w in (* return address *)
  let sz := oretaddr + w in (* total size *)
  {| fe_size := sz;
     fe_ofs_link := olink;
     fe_ofs_retaddr := oretaddr;
     fe_ofs_local := ol;
     fe_ofs_callee_save := ocs;
     fe_stack_data := ostkdata;
     fe_used_callee_save := b.(used_callee_save) |}.

Lemma frame_env_range: forall b, let fe := make_env b in 0 <= fe_stack_data fe /\ fe_stack_data fe + bound_stack_data b <= fe_size fe.