(* *********************************************************************)
(*                                                                     *)
(*              The Compcert verified compiler                         *)
(*                                                                     *)
(*         Xavier Leroy, Collège de France and INRIA Paris             *)
(*                                                                     *)
(*  Copyright Institut National de Recherche en Informatique et en     *)
(*  Automatique.  All rights reserved.  This file is distributed       *)
(*  under the terms of the INRIA Non-Commercial License Agreement.     *)
(*                                                                     *)
(* *********************************************************************)
(** Machine- and ABI-dependent layout information for activation records. *)
Local Open Scope sep_scope.
(** 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 - Return address - Saved values of callee-save registers used by the function. - Local stack slots. - Space for the stack-allocated data declared in Cminor.  The stack pointer is kept 16-aligned. *)
Definition fe_ofs_arg := 0.
Definition make_env (b: bounds) : frame_env :=
let olink := align (4 * b.(bound_outgoing)) 8 in  (* back link *)
let oretaddr := olink + 8 in                      (* return address *)
let ocs := oretaddr + 8 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 sz := align (ostkdata + b.(bound_stack_data)) 16 in
{| 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_aligned:
forall b,
let fe := make_env b in
(8 | fe_ofs_arg)
/\ (8 | fe_ofs_local fe)
/\ (8 | fe_stack_data fe)
/\ (align_chunk Mptr | fe_ofs_link fe)
/\ (align_chunk Mptr | fe_ofs_retaddr fe).