(**************************************************************************)
(*                                                                        *)
(*                                 OCaml                                  *)
(*                                                                        *)
(*             Xavier Leroy, projet Cristal, INRIA Rocquencourt           *)
(*                                                                        *)
(*   Copyright 1996 Institut National de Recherche en Informatique et     *)
(*     en Automatique.                                                    *)
(*                                                                        *)
(*   All rights reserved.  This file is distributed under the terms of    *)
(*   the GNU Lesser General Public License version 2.1, with the          *)
(*   special exception on linking described in the file LICENSE.          *)
(*                                                                        *)
(**************************************************************************)

(* A variant of the "lambda" code with direct / indirect calls explicit
   and closures explicit too *)

open Asttypes
open Lambda

type function_label = string

type ustructured_constant =
  | Uconst_float of float
  | Uconst_int32 of int32
  | Uconst_int64 of int64
  | Uconst_nativeint of nativeint
  | Uconst_block of int * uconstant list
  | Uconst_float_array of float list
  | Uconst_string of string
  | Uconst_closure of ufunction list * string * uconstant list

and uconstant =
  | Uconst_ref of string * ustructured_constant option
  | Uconst_int of int

and uphantom_defining_expr =
  | Uphantom_const of uconstant
  | Uphantom_var of Backend_var.t
  | Uphantom_offset_var of { var : Backend_var.t; offset_in_words : int; }
  | Uphantom_read_field of { var : Backend_var.t; field : int; }
  | Uphantom_read_symbol_field of { sym : string; field : int; }
  | Uphantom_block of { tag : int; fields : Backend_var.t list; }

and ulambda =
    Uvar of Backend_var.t
  | Uconst of uconstant
  | Udirect_apply of function_label * ulambda list * Debuginfo.t
  | Ugeneric_apply of ulambda * ulambda list * Debuginfo.t
  | Uclosure of ufunction list * ulambda list
  | Uoffset of ulambda * int
  | Ulet of mutable_flag * value_kind * Backend_var.With_provenance.t
      * ulambda * ulambda
  | Uphantom_let of Backend_var.With_provenance.t
      * uphantom_defining_expr option * ulambda
  | Uletrec of (Backend_var.With_provenance.t * ulambda) list * ulambda
  | Uprim of Clambda_primitives.primitive * ulambda list * Debuginfo.t
  | Uswitch of ulambda * ulambda_switch * Debuginfo.t
  | Ustringswitch of ulambda * (string * ulambda) list * ulambda option
  | Ustaticfail of int * ulambda list
  | Ucatch of
      int *
      (Backend_var.With_provenance.t * value_kind) list *
      ulambda *
      ulambda
  | Utrywith of ulambda * Backend_var.With_provenance.t * ulambda
  | Uifthenelse of ulambda * ulambda * ulambda
  | Usequence of ulambda * ulambda
  | Uwhile of ulambda * ulambda
  | Ufor of Backend_var.With_provenance.t * ulambda * ulambda
      * direction_flag * ulambda
  | Uassign of Backend_var.t * ulambda
  | Usend of meth_kind * ulambda * ulambda * ulambda list * Debuginfo.t
  | Uunreachable

and ufunction = {
  label  : function_label;
  arity  : int;
  params : (Backend_var.With_provenance.t * value_kind) list;
  return : value_kind;
  body   : ulambda;
  dbg    : Debuginfo.t;
  env    : Backend_var.t option;
}

and ulambda_switch =
  { us_index_consts: int array;
    us_actions_consts : ulambda array;
    us_index_blocks: int array;
    us_actions_blocks: ulambda array}

(* Description of known functions *)

type function_description =
  { fun_label: function_label;          (* Label of direct entry point *)
    fun_arity: int;                     (* Number of arguments *)
    mutable fun_closed: bool;           (* True if environment not used *)
    mutable fun_inline: (Backend_var.With_provenance.t list * ulambda) option;
    mutable fun_float_const_prop: bool  (* Can propagate FP consts *)
  }

(* Approximation of values *)

type value_approximation =
    Value_closure of function_description * value_approximation
  | Value_tuple of value_approximation array
  | Value_unknown
  | Value_const of uconstant
  | Value_global_field of string * int

(* Preallocated globals *)

type usymbol_provenance = {
  original_idents : Ident.t list;
  module_path : Path.t;
}

type uconstant_block_field =
  | Uconst_field_ref of string
  | Uconst_field_int of int

type preallocated_block = {
  symbol : string;
  exported : bool;
  tag : int;
  fields : uconstant_block_field option list;
  provenance : usymbol_provenance option;
}

type preallocated_constant = {
  symbol : string;
  exported : bool;
  definition : ustructured_constant;
  provenance : usymbol_provenance option;
}

type with_constants =
  ulambda * preallocated_block list * preallocated_constant list

(* Comparison functions for constants.  We must not use Stdlib.compare
   because it compares "0.0" and "-0.0" equal.  (PR#6442) *)

let compare_floats x1 x2 =
  Int64.compare (Int64.bits_of_float x1) (Int64.bits_of_float x2)

let rec compare_float_lists l1 l2 =
  match l1, l2 with
  | [], [] -> 0
  | [], _::_ -> -1
  | _::_, [] -> 1
  | h1::t1, h2::t2 ->
      let c = compare_floats h1 h2 in
      if c <> 0 then c else compare_float_lists t1 t2

let compare_constants c1 c2 =
  match c1, c2 with
  | Uconst_ref(lbl1, _c1), Uconst_ref(lbl2, _c2) -> String.compare lbl1 lbl2
      (* Same labels -> same constants.
         Different labels -> different constants, even if the contents
           match, because of string constants that must not be
           reshared. *)
  | Uconst_int n1, Uconst_int n2 -> Stdlib.compare n1 n2
  | Uconst_ref _, _ -> -1
  | Uconst_int _, Uconst_ref _ -> 1

let rec compare_constant_lists l1 l2 =
  match l1, l2 with
  | [], [] -> 0
  | [], _::_ -> -1
  | _::_, [] -> 1
  | h1::t1, h2::t2 ->
      let c = compare_constants h1 h2 in
      if c <> 0 then c else compare_constant_lists t1 t2

let rank_structured_constant = function
  | Uconst_float _ -> 0
  | Uconst_int32 _ -> 1
  | Uconst_int64 _ -> 2
  | Uconst_nativeint _ -> 3
  | Uconst_block _ -> 4
  | Uconst_float_array _ -> 5
  | Uconst_string _ -> 6
  | Uconst_closure _ -> 7

let compare_structured_constants c1 c2 =
  match c1, c2 with
  | Uconst_float x1, Uconst_float x2 -> compare_floats x1 x2
  | Uconst_int32 x1, Uconst_int32 x2 -> Int32.compare x1 x2
  | Uconst_int64 x1, Uconst_int64 x2 -> Int64.compare x1 x2
  | Uconst_nativeint x1, Uconst_nativeint x2 -> Nativeint.compare x1 x2
  | Uconst_block(t1, l1), Uconst_block(t2, l2) ->
      let c = t1 - t2 (* no overflow possible here *) in
      if c <> 0 then c else compare_constant_lists l1 l2
  | Uconst_float_array l1, Uconst_float_array l2 ->
      compare_float_lists l1 l2
  | Uconst_string s1, Uconst_string s2 -> String.compare s1 s2
  | Uconst_closure (_,lbl1,_), Uconst_closure (_,lbl2,_) ->
      String.compare lbl1 lbl2
  | _, _ ->
    (* no overflow possible here *)
    rank_structured_constant c1 - rank_structured_constant c2