(* *********************************************************************)
(*                                                                     *)
(*              The Compcert verified compiler                         *)
(*                                                                     *)
(*          Xavier Leroy, INRIA Paris-Rocquencourt                     *)
(*                                                                     *)
(*  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. *)
(** The general shape of activation records is as follows, from bottom (lowest offsets) to top: - Space for outgoing arguments to function calls. - Pointer to activation record of the caller. - Saved return address into caller. - Local stack slots. - Saved values of callee-save registers used by the function. - Space for the stack-allocated data declared in Cminor.  The [frame_env] compilation environment records the positions of the boundaries between areas in the frame part. *)
Definition fe_ofs_arg := 0.
(** Computation of the frame environment from the bounds of the current function. *)
Definition make_env (b: bounds) :=
let olink := 4 * b.(bound_outgoing) in  (* back link*)
let ora := olink + 4 in (* return address *)
let ol := align (ora + 4) 8 in    (* locals *)
let ocs := ol + 4 * b.(bound_local) in (* callee-saves *)
let ostkdata := align (size_callee_save_area b ocs) 8 in (* retaddr *)
let sz := align (ostkdata + b.(bound_stack_data)) 8 in
{| fe_size := sz;
fe_ofs_link := olink;
fe_ofs_retaddr := ora;
fe_ofs_local := ol;
fe_ofs_callee_save := ocs;
fe_stack_data := ostkdata;
fe_used_callee_save := b.(used_callee_save) |}.
(** Separation property *)
Local Open Scope sep_scope.

(* Specifications: *)
Lemma frame_env_separated:
forall b sp m P,
let fe := make_env b in
m |= range sp 0 (fe_stack_data fe) ** range sp (fe_stack_data fe + bound_stack_data b) (fe_size fe) ** P ->
m |= range sp (fe_ofs_local fe) (fe_ofs_local fe + 4 * bound_local b)
** range sp fe_ofs_arg (fe_ofs_arg + 4 * bound_outgoing b)
** range sp (fe_ofs_link fe) (fe_ofs_link fe + 4)
** range sp (fe_ofs_retaddr fe) (fe_ofs_retaddr fe + 4)
** range sp (fe_ofs_callee_save fe) (size_callee_save_area b (fe_ofs_callee_save fe))
** P.
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.
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)
/\ (4 | fe_ofs_link fe)
/\ (4 | fe_ofs_retaddr fe).