(* *********************************************************************)
(*                                                                     *)
(*              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.     *)
(*                                                                     *)
(* *********************************************************************)
(** Correctness proof for Asm generation: machine-independent framework *)
Require Intv.
(** * Processor registers and register states *)
Hint Extern 2 (_ <> _) => congruence: asmgen.
Hint Resolve preg_of_data: asmgen.
Hint Resolve data_diff: asmgen.
Hint Resolve preg_of_not_SP preg_of_not_PC: asmgen.
Fixpoint preg_notin (r: preg) (rl: list mreg) : Prop :=
match rl with
| nil => True
| r1 :: nil => r <> preg_of r1
| r1 :: rl => r <> preg_of r1 /\ preg_notin r rl
end.
Remark preg_notin_charact:
forall r rl,
preg_notin r rl <-> (forall mr, In mr rl -> r <> preg_of mr).
(** * Agreement between Mach registers and processor registers *)
Record agree (ms: Mach.regset) (sp: val) (rs: Asm.regset) : Prop := mkagree {
agree_sp: rs#SP = sp;
agree_sp_def: sp <> Vundef;
agree_mregs: forall r: mreg, Val.lessdef (ms r) (rs#(preg_of r))
}.
(** Preservation of register agreement under various assignments. *)
(** Connection between Mach and Asm calling conventions for external functions. *)
(** Translation of arguments and results to builtins. *)
Remark builtin_arg_match:
forall ge (rs: regset) sp m a v,
eval_builtin_arg ge (fun r => rs (preg_of r)) sp m a v ->
eval_builtin_arg ge rs sp m (map_builtin_arg preg_of a) v.
(** * Correspondence between Mach code and Asm code *)
(** The ``code tail'' of an instruction list [c] is the list of instructions starting at PC [pos]. *)
Inductive code_tail: Z -> code -> code -> Prop :=
| code_tail_0: forall c,
code_tail 0 c c
| code_tail_S: forall pos i c1 c2,
code_tail pos c1 c2 ->
code_tail (pos + 1) (i :: c1) c2.
Remark code_tail_bounds_1:
forall fn ofs c,
code_tail ofs fn c -> 0 <= ofs <= list_length_z fn.
Remark code_tail_bounds_2:
forall fn ofs i c,
code_tail ofs fn (i :: c) -> 0 <= ofs < list_length_z fn.

Lemma code_tail_next_int:
forall fn ofs i c,
list_length_z fn <= Ptrofs.max_unsigned ->
code_tail (Ptrofs.unsigned ofs) fn (i :: c) ->
code_tail (Ptrofs.unsigned (Ptrofs.add ofs Ptrofs.one)) fn c.