path: root/common/AST.v

(* *********************************************************************)
(*                                                                     *)
(*              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 GNU General Public License as published by  *)
(*  the Free Software Foundation, either version 2 of the License, or  *)
(*  (at your option) any later version.  This file is also distributed *)
(*  under the terms of the INRIA Non-Commercial License Agreement.     *)
(*                                                                     *)
(* *********************************************************************)

(** This file defines a number of data types and operations used in
  the abstract syntax trees of many of the intermediate languages. *)

Require Import Coqlib.
Require String.
Require Import Errors.
Require Import Integers.
Require Import Floats.

Set Implicit Arguments.

(** * Syntactic elements *)

(** Identifiers (names of local variables, of global symbols and functions,
  etc) are represented by the type [positive] of positive integers. *)

Definition ident := positive.

Definition ident_eq := peq.

Parameter ident_of_string : String.string -> ident.

(** The intermediate languages are weakly typed, using only four
  types: [Tint] for 32-bit integers and pointers, [Tfloat] for 64-bit
  floating-point numbers, [Tlong] for 64-bit integers, [Tsingle]
  for 32-bit floating-point numbers. *)

Inductive typ : Type :=
  | Tint
  | Tfloat
  | Tlong
  | Tsingle.

Definition typesize (ty: typ) : Z :=
  match ty with Tint => 4 | Tfloat => 8 | Tlong => 8 | Tsingle => 4 end.

Lemma typesize_pos: forall ty, typesize ty > 0.
Proof. destruct ty; simpl; omega. Qed.

Lemma typ_eq: forall (t1 t2: typ), {t1=t2} + {t1<>t2}.
Proof. decide equality. Defined.
Global Opaque typ_eq.

Definition opt_typ_eq: forall (t1 t2: option typ), {t1=t2} + {t1<>t2}
                     := option_eq typ_eq.

Definition list_typ_eq: forall (l1 l2: list typ), {l1=l2} + {l1<>l2}
                     := list_eq_dec typ_eq.

(** All values of type [Tsingle] are also of type [Tfloat].  This
  corresponds to the following subtyping relation over types. *)

Definition subtype (ty1 ty2: typ) : bool :=
  match ty1, ty2 with
  | Tint, Tint => true
  | Tlong, Tlong => true
  | Tfloat, Tfloat => true
  | Tsingle, Tsingle => true
  | Tsingle, Tfloat => true
  | _, _ => false
  end.

Fixpoint subtype_list (tyl1 tyl2: list typ) : bool :=
  match tyl1, tyl2 with
  | nil, nil => true
  | ty1::tys1, ty2::tys2 => subtype ty1 ty2 && subtype_list tys1 tys2
  | _, _ => false
  end.

(** Additionally, function definitions and function calls are annotated
  by function signatures indicating the number and types of arguments,
  as well as the type of the returned value if any.  These signatures
  are used in particular to determine appropriate calling conventions
  for the function. *)

Record signature : Type := mksignature {
  sig_args: list typ;
  sig_res: option typ
}.

Definition proj_sig_res (s: signature) : typ :=
  match s.(sig_res) with
  | None => Tint
  | Some t => t
  end.

Definition signature_eq: forall (s1 s2: signature), {s1=s2} + {s1<>s2}.
Proof. generalize opt_typ_eq, list_typ_eq; intros; decide equality. Defined.
Global Opaque signature_eq.

(** Memory accesses (load and store instructions) are annotated by
  a ``memory chunk'' indicating the type, size and signedness of the
  chunk of memory being accessed. *)

Inductive memory_chunk : Type :=
  | Mint8signed     (**r 8-bit signed integer *)
  | Mint8unsigned   (**r 8-bit unsigned integer *)
  | Mint16signed    (**r 16-bit signed integer *)
  | Mint16unsigned  (**r 16-bit unsigned integer *)
  | Mint32          (**r 32-bit integer, or pointer *)
  | Mint64          (**r 64-bit integer *)
  | Mfloat32        (**r 32-bit single-precision float *)
  | Mfloat64        (**r 64-bit double-precision float *)
  | Mfloat64al32.   (**r 64-bit double-precision float, 4-aligned *)

Definition chunk_eq: forall (c1 c2: memory_chunk), {c1=c2} + {c1<>c2}.
Proof. decide equality. Defined.
Global Opaque chunk_eq.

(** The type (integer/pointer or float) of a chunk. *)

Definition type_of_chunk (c: memory_chunk) : typ :=
  match c with
  | Mint8signed => Tint
  | Mint8unsigned => Tint
  | Mint16signed => Tint
  | Mint16unsigned => Tint
  | Mint32 => Tint
  | Mint64 => Tlong
  | Mfloat32 => Tsingle
  | Mfloat64 => Tfloat
  | Mfloat64al32 => Tfloat
  end.

Definition type_of_chunk_use (c: memory_chunk) : typ :=
  match c with
  | Mint8signed => Tint
  | Mint8unsigned => Tint
  | Mint16signed => Tint
  | Mint16unsigned => Tint
  | Mint32 => Tint
  | Mint64 => Tlong
  | Mfloat32 => Tfloat
  | Mfloat64 => Tfloat
  | Mfloat64al32 => Tfloat
  end.

(** The chunk that is appropriate to store and reload a value of
  the given type, without losing information. *)

Definition chunk_of_type (ty: typ) :=
  match ty with
  | Tint => Mint32
  | Tfloat => Mfloat64al32
  | Tlong => Mint64
  | Tsingle => Mfloat32
  end.

(** Initialization data for global variables. *)

Inductive init_data: Type :=
  | Init_int8: int -> init_data
  | Init_int16: int -> init_data
  | Init_int32: int -> init_data
  | Init_int64: int64 -> init_data
  | Init_float32: float -> init_data
  | Init_float64: float -> init_data
  | Init_space: Z -> init_data
  | Init_addrof: ident -> int -> init_data.  (**r address of symbol + offset *)

(** Information attached to global variables. *)

Record globvar (V: Type) : Type := mkglobvar {
  gvar_info: V;                    (**r language-dependent info, e.g. a type *)
  gvar_init: list init_data;       (**r initialization data *)
  gvar_readonly: bool;             (**r read-only variable? (const) *)
  gvar_volatile: bool              (**r volatile variable? *)
}.

(** Whole programs consist of:
- a collection of global definitions (name and description);
- the name of the ``main'' function that serves as entry point in the program.

A global definition is either a global function or a global variable.
The type of function descriptions and that of additional information
for variables vary among the various intermediate languages and are
taken as parameters to the [program] type.  The other parts of whole
programs are common to all languages. *)

Inductive globdef (F V: Type) : Type :=
  | Gfun (f: F)
  | Gvar (v: globvar V).

Implicit Arguments Gfun [F V].
Implicit Arguments Gvar [F V].

Record program (F V: Type) : Type := mkprogram {
  prog_defs: list (ident * globdef F V);
  prog_main: ident
}.

Definition prog_defs_names (F V: Type) (p: program F V) : list ident :=
  List.map fst p.(prog_defs).

(** * Generic transformations over programs *)

(** We now define a general iterator over programs that applies a given
  code transformation function to all function descriptions and leaves
  the other parts of the program unchanged. *)

Section TRANSF_PROGRAM.

Variable A B V: Type.
Variable transf: A -> B.

Definition transform_program_globdef (idg: ident * globdef A V) : ident * globdef B V :=
  match idg with
  | (id, Gfun f) => (id, Gfun (transf f))
  | (id, Gvar v) => (id, Gvar v)
  end.

Definition transform_program (p: program A V) : program B V :=
  mkprogram
    (List.map transform_program_globdef p.(prog_defs))
    p.(prog_main).

Lemma transform_program_function:
  forall p i tf,
  In (i, Gfun tf) (transform_program p).(prog_defs) ->
  exists f, In (i, Gfun f) p.(prog_defs) /\ transf f = tf.
Proof.
  simpl. unfold transform_program. intros.
  exploit list_in_map_inv; eauto. 
  intros [[i' gd] [EQ IN]]. simpl in EQ. destruct gd; inv EQ. 
  exists f; auto.
Qed.

End TRANSF_PROGRAM.

(** The following is a more general presentation of [transform_program] where 
  global variable information can be transformed, in addition to function
  definitions.  Moreover, the transformation functions can fail and
  return an error message. *)

Open Local Scope error_monad_scope.
Open Local Scope string_scope.

Section TRANSF_PROGRAM_GEN.

Variables A B V W: Type.
Variable transf_fun: A -> res B.
Variable transf_var: V -> res W.

Definition transf_globvar (g: globvar V) : res (globvar W) :=
  do info' <- transf_var g.(gvar_info);
  OK (mkglobvar info' g.(gvar_init) g.(gvar_readonly) g.(gvar_volatile)).

Fixpoint transf_globdefs (l: list (ident * globdef A V)) : res (list (ident * globdef B W)) :=
  match l with
  | nil => OK nil
  | (id, Gfun f) :: l' =>
      match transf_fun f with
      | Error msg => Error (MSG "In function " :: CTX id :: MSG ": " :: msg)
      | OK tf =>
          do tl' <- transf_globdefs l'; OK ((id, Gfun tf) :: tl')
      end
  | (id, Gvar v) :: l' =>
      match transf_globvar v with
      | Error msg => Error (MSG "In variable " :: CTX id :: MSG ": " :: msg)
      | OK tv =>
          do tl' <- transf_globdefs l'; OK ((id, Gvar tv) :: tl')
      end
  end.

Definition transform_partial_program2 (p: program A V) : res (program B W) :=
  do gl' <- transf_globdefs p.(prog_defs); OK(mkprogram gl' p.(prog_main)).

Lemma transform_partial_program2_function:
  forall p tp i tf,
  transform_partial_program2 p = OK tp ->
  In (i, Gfun tf) tp.(prog_defs) ->
  exists f, In (i, Gfun f) p.(prog_defs) /\ transf_fun f = OK tf.
Proof.
  intros. monadInv H. simpl in H0. 
  revert x EQ H0. induction (prog_defs p); simpl; intros.
  inv EQ. contradiction.
  destruct a as [id [f|v]].
  destruct (transf_fun f) as [tf1|msg] eqn:?; monadInv EQ.
  simpl in H0; destruct H0. inv H. exists f; auto. 
  exploit IHl; eauto. intros [f' [P Q]]; exists f'; auto.
  destruct (transf_globvar v) as [tv1|msg] eqn:?; monadInv EQ.
  simpl in H0; destruct H0. inv H.
  exploit IHl; eauto. intros [f' [P Q]]; exists f'; auto.
Qed.

Lemma transform_partial_program2_variable:
  forall p tp i tv,
  transform_partial_program2 p = OK tp ->
  In (i, Gvar tv) tp.(prog_defs) ->
  exists v,
     In (i, Gvar(mkglobvar v tv.(gvar_init) tv.(gvar_readonly) tv.(gvar_volatile))) p.(prog_defs)
  /\ transf_var v = OK tv.(gvar_info).
Proof.
  intros. monadInv H. simpl in H0. 
  revert x EQ H0. induction (prog_defs p); simpl; intros.
  inv EQ. contradiction.
  destruct a as [id [f|v]].
  destruct (transf_fun f) as [tf1|msg] eqn:?; monadInv EQ.
  simpl in H0; destruct H0. inv H.
  exploit IHl; eauto. intros [v' [P Q]]; exists v'; auto.
  destruct (transf_globvar v) as [tv1|msg] eqn:?; monadInv EQ.
  simpl in H0; destruct H0. inv H.
  monadInv Heqr. simpl. exists (gvar_info v). split. left. destruct v; auto. auto.
  exploit IHl; eauto. intros [v' [P Q]]; exists v'; auto.
Qed.

Lemma transform_partial_program2_succeeds:
  forall p tp i g,
  transform_partial_program2 p = OK tp ->
  In (i, g) p.(prog_defs) ->
  match g with
  | Gfun fd => exists tfd, transf_fun fd = OK tfd
  | Gvar gv => exists tv, transf_var gv.(gvar_info) = OK tv
  end.
Proof.
  intros. monadInv H. 
  revert x EQ H0. induction (prog_defs p); simpl; intros.
  contradiction.
  destruct a as [id1 g1]. destruct g1.
  destruct (transf_fun f) eqn:TF; try discriminate. monadInv EQ. 
  destruct H0. inv H. econstructor; eauto. eapply IHl; eauto.
  destruct (transf_globvar v) eqn:TV; try discriminate. monadInv EQ.
  destruct H0. inv H. monadInv TV. econstructor; eauto. eapply IHl; eauto.
Qed.

Lemma transform_partial_program2_main:
  forall p tp,
  transform_partial_program2 p = OK tp ->
  tp.(prog_main) = p.(prog_main).
Proof.
  intros. monadInv H. reflexivity.
Qed.

(** Additionally, we can also "augment" the program with new global definitions
  and a different "main" function. *)

Section AUGMENT.

Variable new_globs: list(ident * globdef B W).
Variable new_main: ident.

Definition transform_partial_augment_program (p: program A V) : res (program B W) :=
  do gl' <- transf_globdefs p.(prog_defs);
  OK(mkprogram (gl' ++ new_globs) new_main).

Lemma transform_partial_augment_program_main:
  forall p tp,
  transform_partial_augment_program p = OK tp ->
  tp.(prog_main) = new_main.
Proof.
  intros. monadInv H. reflexivity.
Qed.

End AUGMENT.

Remark transform_partial_program2_augment:
  forall p,
  transform_partial_program2 p =
  transform_partial_augment_program nil p.(prog_main) p.
Proof.
  unfold transform_partial_program2, transform_partial_augment_program; intros.
  destruct (transf_globdefs (prog_defs p)); auto.
  simpl. f_equal. f_equal. rewrite <- app_nil_end. auto.
Qed.

End TRANSF_PROGRAM_GEN.

(** The following is a special case of [transform_partial_program2],
  where only function definitions are transformed, but not variable definitions. *)

Section TRANSF_PARTIAL_PROGRAM.

Variable A B V: Type.
Variable transf_partial: A -> res B.

Definition transform_partial_program (p: program A V) : res (program B V) :=
  transform_partial_program2 transf_partial (fun v => OK v) p.

Lemma transform_partial_program_main:
  forall p tp,
  transform_partial_program p = OK tp ->
  tp.(prog_main) = p.(prog_main).
Proof.
  apply transform_partial_program2_main.
Qed.

Lemma transform_partial_program_function:
  forall p tp i tf,
  transform_partial_program p = OK tp ->
  In (i, Gfun tf) tp.(prog_defs) ->
  exists f, In (i, Gfun f) p.(prog_defs) /\ transf_partial f = OK tf.
Proof.
  apply transform_partial_program2_function. 
Qed.

Lemma transform_partial_program_succeeds:
  forall p tp i fd,
  transform_partial_program p = OK tp ->
  In (i, Gfun fd) p.(prog_defs) ->
  exists tfd, transf_partial fd = OK tfd.
Proof.
  unfold transform_partial_program; intros. 
  exploit transform_partial_program2_succeeds; eauto. 
Qed.

End TRANSF_PARTIAL_PROGRAM.

Lemma transform_program_partial_program:
  forall (A B V: Type) (transf: A -> B) (p: program A V),
  transform_partial_program (fun f => OK(transf f)) p = OK(transform_program transf p).
Proof.
  intros.
  unfold transform_partial_program, transform_partial_program2, transform_program; intros.
  replace (transf_globdefs (fun f => OK (transf f)) (fun v => OK v) p.(prog_defs))
     with (OK (map (transform_program_globdef transf) p.(prog_defs))).
  auto. 
  induction (prog_defs p); simpl.
  auto.
  destruct a as [id [f|v]]; rewrite <- IHl.
    auto.
    destruct v; auto.
Qed.

(** The following is a relational presentation of 
  [transform_partial_augment_preogram].  Given relations between function
  definitions and between variable information, it defines a relation
  between programs stating that the two programs have appropriately related
  shapes (global names are preserved and possibly augmented, etc) 
  and that identically-named function definitions
  and variable information are related. *)

Section MATCH_PROGRAM.

Variable A B V W: Type.
Variable match_fundef: A -> B -> Prop.
Variable match_varinfo: V -> W -> Prop.

Inductive match_globdef: ident * globdef A V -> ident * globdef B W -> Prop :=
  | match_glob_fun: forall id f1 f2,
      match_fundef f1 f2 ->
      match_globdef (id, Gfun f1) (id, Gfun f2)
  | match_glob_var: forall id init ro vo info1 info2,
      match_varinfo info1 info2 ->
      match_globdef (id, Gvar (mkglobvar info1 init ro vo)) (id, Gvar (mkglobvar info2 init ro vo)).

Definition match_program (new_globs : list (ident * globdef B W))
                         (new_main : ident)
                         (p1: program A V)  (p2: program B W) : Prop :=
  (exists tglob, list_forall2 match_globdef p1.(prog_defs) tglob /\
                 p2.(prog_defs) = tglob ++ new_globs) /\
  p2.(prog_main) = new_main.

End MATCH_PROGRAM.

Lemma transform_partial_augment_program_match:
  forall (A B V W: Type)
         (transf_fun: A -> res B)
         (transf_var: V -> res W)
         (p: program A V) 
         (new_globs : list (ident * globdef B W))
         (new_main : ident)
         (tp: program B W),
  transform_partial_augment_program transf_fun transf_var new_globs new_main p = OK tp ->
  match_program 
    (fun fd tfd => transf_fun fd = OK tfd)
    (fun info tinfo => transf_var info = OK tinfo)
    new_globs new_main
    p tp.
Proof.
  unfold transform_partial_augment_program; intros. monadInv H. 
  red; simpl. split; auto. exists x; split; auto.
  revert x EQ. generalize (prog_defs p). induction l; simpl; intros.
  monadInv EQ. constructor.
  destruct a as [id [f|v]]. 
  (* function *)
  destruct (transf_fun f) as [tf|?] eqn:?; monadInv EQ. 
  constructor; auto. constructor; auto.
  (* variable *)
  unfold transf_globvar in EQ.
  destruct (transf_var (gvar_info v)) as [tinfo|?] eqn:?; simpl in EQ; monadInv EQ.
  constructor; auto. destruct v; simpl in *. constructor; auto.
Qed.

(** * External functions *)

(** For most languages, the functions composing the program are either
  internal functions, defined within the language, or external functions,
  defined outside.  External functions include system calls but also
  compiler built-in functions.  We define a type for external functions
  and associated operations. *)

Inductive external_function : Type :=
  | EF_external (name: ident) (sg: signature)
     (** A system call or library function.  Produces an event
         in the trace. *)
  | EF_builtin (name: ident) (sg: signature)
     (** A compiler built-in function.  Behaves like an external, but
         can be inlined by the compiler. *)
  | EF_vload (chunk: memory_chunk)
     (** A volatile read operation.  If the adress given as first argument
         points within a volatile global variable, generate an
         event and return the value found in this event.  Otherwise,
         produce no event and behave like a regular memory load. *)
  | EF_vstore (chunk: memory_chunk)
     (** A volatile store operation.   If the adress given as first argument
         points within a volatile global variable, generate an event.
         Otherwise, produce no event and behave like a regular memory store. *)
  | EF_vload_global (chunk: memory_chunk) (id: ident) (ofs: int)
     (** A volatile load operation from a global variable. 
         Specialized version of [EF_vload]. *)
  | EF_vstore_global (chunk: memory_chunk) (id: ident) (ofs: int)
     (** A volatile store operation in a global variable. 
         Specialized version of [EF_vstore]. *)
  | EF_malloc
     (** Dynamic memory allocation.  Takes the requested size in bytes
         as argument; returns a pointer to a fresh block of the given size.
         Produces no observable event. *)
  | EF_free
     (** Dynamic memory deallocation.  Takes a pointer to a block
         allocated by an [EF_malloc] external call and frees the
         corresponding block.
         Produces no observable event. *)
  | EF_memcpy (sz: Z) (al: Z)
     (** Block copy, of [sz] bytes, between addresses that are [al]-aligned. *)
  | EF_annot (text: ident) (targs: list annot_arg)
     (** A programmer-supplied annotation.  Takes zero, one or several arguments,
         produces an event carrying the text and the values of these arguments,
         and returns no value. *)
  | EF_annot_val (text: ident) (targ: typ)
     (** Another form of annotation that takes one argument, produces
         an event carrying the text and the value of this argument,
         and returns the value of the argument. *)
  | EF_inline_asm (text: ident)
     (** Inline [asm] statements.  Semantically, treated like an
         annotation with no parameters ([EF_annot text nil]).  To be
         used with caution, as it can invalidate the semantic
         preservation theorem.  Generated only if [-finline-asm] is
         given. *)

with annot_arg : Type :=
  | AA_arg (ty: typ)
  | AA_int (n: int)
  | AA_float (n: float).

(** The type signature of an external function. *)

Fixpoint annot_args_typ (targs: list annot_arg) : list typ :=
  match targs with
  | nil => nil
  | AA_arg ty :: targs' => ty :: annot_args_typ targs'
  | _ :: targs' => annot_args_typ targs'
  end.

Definition ef_sig (ef: external_function): signature :=
  match ef with
  | EF_external name sg => sg
  | EF_builtin name sg => sg
  | EF_vload chunk => mksignature (Tint :: nil) (Some (type_of_chunk chunk))
  | EF_vstore chunk => mksignature (Tint :: type_of_chunk chunk :: nil) None
  | EF_vload_global chunk _ _ => mksignature nil (Some (type_of_chunk chunk))
  | EF_vstore_global chunk _ _ => mksignature (type_of_chunk chunk :: nil) None
  | EF_malloc => mksignature (Tint :: nil) (Some Tint)
  | EF_free => mksignature (Tint :: nil) None
  | EF_memcpy sz al => mksignature (Tint :: Tint :: nil) None
  | EF_annot text targs => mksignature (annot_args_typ targs) None
  | EF_annot_val text targ => mksignature (targ :: nil) (Some targ)
  | EF_inline_asm text => mksignature nil None
  end.

(** Whether an external function should be inlined by the compiler. *)

Definition ef_inline (ef: external_function) : bool :=
  match ef with
  | EF_external name sg => false
  | EF_builtin name sg => true
  | EF_vload chunk => true
  | EF_vstore chunk => true
  | EF_vload_global chunk id ofs => true
  | EF_vstore_global chunk id ofs => true
  | EF_malloc => false
  | EF_free => false
  | EF_memcpy sz al => true
  | EF_annot text targs => true
  | EF_annot_val text targ => true
  | EF_inline_asm text => true
  end.

(** Whether an external function must reload its arguments. *)

Definition ef_reloads (ef: external_function) : bool :=
  match ef with
  | EF_annot text targs => false
  | _ => true
  end.

(** Equality between external functions.  Used in module [Allocation]. *)

Definition external_function_eq: forall (ef1 ef2: external_function), {ef1=ef2} + {ef1<>ef2}.
Proof.
  generalize ident_eq signature_eq chunk_eq typ_eq zeq Int.eq_dec; intros.
  decide equality.
  apply list_eq_dec. decide equality. apply Float.eq_dec. 
Defined.
Global Opaque external_function_eq.

(** Function definitions are the union of internal and external functions. *)

Inductive fundef (F: Type): Type :=
  | Internal: F -> fundef F
  | External: external_function -> fundef F.

Implicit Arguments External [F].

Section TRANSF_FUNDEF.

Variable A B: Type.
Variable transf: A -> B.

Definition transf_fundef (fd: fundef A): fundef B :=
  match fd with
  | Internal f => Internal (transf f)
  | External ef => External ef
  end.

End TRANSF_FUNDEF.

Section TRANSF_PARTIAL_FUNDEF.

Variable A B: Type.
Variable transf_partial: A -> res B.

Definition transf_partial_fundef (fd: fundef A): res (fundef B) :=
  match fd with
  | Internal f => do f' <- transf_partial f; OK (Internal f')
  | External ef => OK (External ef)
  end.

End TRANSF_PARTIAL_FUNDEF.