(* *********************************************************************)
(* *)
(* 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. *)
(* *)
(* *********************************************************************)
(** Locations are a refinement of RTL pseudo-registers, used to reflect
the results of register allocation (file [Allocation]). *)
Require Import OrderedType. Require Import Coqlib. Require Import Maps. Require Import Ordered. Require Import AST. Require Import Values. Require Export Machregs. (** * Representation of locations *)
(** A location is either a processor register or (an abstract designation of)
a slot in the activation record of the current function. *)
(** ** Processor registers *)
(** Processor registers usable for register allocation are defined
in module [Machregs]. *)
(** ** Slots in activation records *)
(** A slot in an activation record is designated abstractly by a kind,
a type and an integer offset. Three kinds are considered:
- [Local]: these are the slots used by register allocation for
pseudo-registers that cannot be assigned a hardware register.
- [Incoming]: used to store the parameters of the current function
that cannot reside in hardware registers, as determined by the
calling conventions.
- [Outgoing]: used to store arguments to called functions that
cannot reside in hardware registers, as determined by the
calling conventions. *)
Inductive slot: Type :=
| Local
| Incoming
| Outgoing.
(** ** Locations *)
(** Locations are just the disjoint union of machine registers and
activation record slots. *)
Inductive loc : Type :=
| R (r: mreg)
| S (sl: slot) (pos: Z) (ty: typ). Module Loc. Definition type (l: loc) : typ :=
match l with
| R r => mreg_type r
| S sl pos ty => ty
end.
(** As mentioned previously, two locations can be different (in the sense
of the [<>] mathematical disequality), yet denote
overlapping memory chunks within the activation record.
Given two locations, three cases are possible:
- They are equal (in the sense of the [=] equality)
- They are different and non-overlapping.
- They are different but overlapping.
The second case (different and non-overlapping) is characterized
by the following [Loc.diff] predicate.
*)
Definition diff (l1 l2: loc) : Prop :=
match l1, l2 with
| R r1, R r2 =>
r1 <> r2
| S s1 d1 t1, S s2 d2 t2 =>
s1 <> s2 \/ d1 + typesize t1 <= d2 \/ d2 + typesize t2 <= d1
| _, _ =>
True
end.
(** We now redefine some standard notions over lists, using the [Loc.diff]
predicate instead of standard disequality [<>].
[Loc.notin l ll] holds if the location [l] is different from all locations
in the list [ll]. *)
Fixpoint notin (l: loc) (ll: list loc) {struct ll} : Prop :=
match ll with
| nil => True
| l1 :: ls => diff l l1 /\ notin l ls
end.
(** [Loc.disjoint l1 l2] is true if the locations in list [l1]
are different from all locations in list [l2]. *)
Definition disjoint (l1 l2: list loc) : Prop :=
forall x1 x2, In x1 l1 -> In x2 l2 -> diff x1 x2.
Proof. intros. rewrite notin_iff. intros. red in H. auto. Qed.
(** [Loc.norepet ll] holds if the locations in list [ll] are pairwise
different. *)
Inductive norepet : list loc -> Prop :=
| norepet_nil:
norepet nil
| norepet_cons:
forall hd tl, notin hd tl -> norepet tl -> norepet (hd :: tl).
Proof. Admitted.
Proof. induction ll. { left. constructor. } { destruct (notin_dec a ll). { destruct IHll. { left. constructor. { auto. } { auto. } } { right. red. intros P. inv P. contradiction. } } { right. red. intros P. inv P. contradiction. } } Defined.
(** [Loc.no_overlap l1 l2] holds if elements of [l1] never overlap partially
with elements of [l2]. *)
Definition no_overlap (l1 l2 : list loc) :=
forall r, In r l1 -> forall s, In s l2 -> r = s \/ Loc.diff r s. End Loc. (** * Mappings from locations to values *)
(** The [Locmap] module defines mappings from locations to values,
used as evaluation environments for the semantics of the [LTL]
and [Linear] intermediate languages. *)
Set Implicit Arguments. Module Locmap. Definition t := loc -> val. Definition init (x: val) : t := fun (_: loc) => x. Definition get (l: loc) (m: t) : val := m l. (** The [set] operation over location mappings reflects the overlapping
properties of locations: changing the value of a location [l]
invalidates (sets to [Vundef]) the locations that partially overlap
with [l]. In other terms, the result of [set l v m]
maps location [l] to value [v], locations that overlap with [l]
to [Vundef], and locations that are different (and non-overlapping)
from [l] to their previous values in [m]. This is apparent in the
``good variables'' properties [Locmap.gss] and [Locmap.gso].
Additionally, the [set] operation also anticipates the fact that
abstract stack slots are mapped to concrete memory locations
in the [Stacking] phase. Hence, values stored in stack slots
are normalized according to the type of the slot. *)
Definition set (l: loc) (v: val) (m: t) : t :=
fun (p: loc) =>
if Loc.eq l p then
match l with R r => v | S sl ofs ty => Val.load_result (chunk_of_type ty) v end
else if Loc.diff_dec l p then
m p
else Vundef.
Proof. assert (P: forall ll l m, m l = Vundef -> (undef ll m) l = Vundef). { induction ll. { simpl. intros. auto. } { simpl. intros. apply IHll. unfold set. destruct (Loc.eq a l). { destruct a. { auto. } { destruct ty. { reflexivity. } { reflexivity. } { reflexivity. } { reflexivity. } { reflexivity. } { reflexivity. } } } { destruct (Loc.diff_dec a l). { auto. } { auto. } } } } { induction ll. { simpl. intros. contradiction. } { simpl. intros. destruct H. { apply P. subst a. apply gss_typed. exact I. } { auto. } } } Qed.
Definition getpair (p: rpair loc) (m: t) : val :=
match p with
| One l => m l
| Twolong l1 l2 => Val.longofwords (m l1) (m l2)
end. Definition setpair (p: rpair mreg) (v: val) (m: t) : t :=
match p with
| One r => set (R r) v m
| Twolong hi lo => set (R lo) (Val.loword v) (set (R hi) (Val.hiword v) m)
end.
Proof. induction p. intros. apply H. simpl. eauto. simpl. intuition. rewrite H. rewrite H. eauto. eauto. eauto. Qed.
Proof. intros. destruct p. { simpl. apply H. simpl. auto. } { simpl. f_equal. { apply H. simpl. auto. } { apply H. simpl. auto. } } Qed.
Proof. Admitted.
Proof. intros. destruct p. { simpl in *. apply gso. apply Loc.diff_sym. auto. } { simpl in *. destruct H. rewrite ! gso. { idtac. auto. } { apply Loc.diff_sym. auto . } { apply Loc.diff_sym. auto . } } Qed.
Fixpoint setres (res: builtin_res mreg) (v: val) (m: t) : t :=
match res with
| BR r => set (R r) v m
| BR_none => m
| BR_splitlong hi lo =>
setres lo (Val.loword v) (setres hi (Val.hiword v) m)
end. End Locmap. (** * Total ordering over locations *)
Module IndexedTyp <: INDEXED_TYPE. Definition t := typ. Definition index (x: t) :=
match x with
| Tany32 => 1%positive
| Tint => 2%positive
| Tsingle => 3%positive
| Tany64 => 4%positive
| Tfloat => 5%positive
| Tlong => 6%positive
end.
Definition eq_dec := Loc.eq. (** Connection between the ordering defined here and the [Loc.diff] predicate. *)
Definition diff_low_bound (l: loc) : loc :=
match l with
| R mr => l
| S sl ofs ty => S sl (ofs - 1) Tany64
end. Definition diff_high_bound (l: loc) : loc :=
match l with
| R mr => l
| S sl ofs ty => S sl (ofs + typesize ty - 1) Tlong
end.