js_op.ml

(* Copyright (C) 2015-2016 Bloomberg Finance L.P.
 * 
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU Lesser General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * In addition to the permissions granted to you by the LGPL, you may combine
 * or link a "work that uses the Library" with a publicly distributed version
 * of this file to produce a combined library or application, then distribute
 * that combined work under the terms of your choosing, with no requirement
 * to comply with the obligations normally placed on you by section 4 of the
 * LGPL version 3 (or the corresponding section of a later version of the LGPL
 * should you choose to use a later version).
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU Lesser General Public License for more details.
 * 
 * You should have received a copy of the GNU Lesser General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA. *)










(** Define some basic types used in JS IR *)

type binop =
  | Eq  
  (* acutally assignment ..
     TODO: move it into statement, so that all expressions 
     are side efffect free (except function calls)
   *)

  | Or
  | And
  | EqEqEq
  | NotEqEq
  (* | InstanceOf *)

  | Lt
  | Le
  | Gt
  | Ge

  | Bor
  | Bxor
  | Band
  | Lsl
  | Lsr
  | Asr

  | Plus
  | Minus
  | Mul
  | Div
  | Mod

(**
note that we don't need raise [Div_by_zero] in BuckleScript

{[
let add x y = x + y  (* | 0 *)
let minus x y = x - y (* | 0 *)
let mul x y = x * y   (* caml_mul | Math.imul *)
let div x y = x / y (* caml_div (x/y|0)*)
let imod x y = x mod y  (* caml_mod (x%y) (zero_divide)*)

let bor x y = x lor y   (* x  | y *)
let bxor x y = x lxor y (* x ^ y *)
let band x y = x land y (* x & y *)
let ilnot  y  = lnot y (* let lnot x = x lxor (-1) *)
let ilsl x y = x lsl y (* x << y*)
let ilsr x y = x lsr y  (* x >>> y | 0 *)
let iasr  x y = x asr y (* x >> y *)
]}


Note that js treat unsigned shift 0 bits in a special way
   Unsigned shifts convert their left-hand side to Uint32, 
   signed shifts convert it to Int32.
   Shifting by 0 digits returns the converted value.
   {[
    function ToUint32(x) {
        return x >>> 0;
    }
    function ToInt32(x) {
        return x >> 0;
    }
   ]}
   So in Js, [-1 >>>0] will be the largest Uint32, while [-1>>0] will remain [-1]
   and [-1 >>> 0 >> 0 ] will be [-1]
*)
type int_op = 
    
  | Bor
  | Bxor
  | Band
  | Lsl
  | Lsr
  | Asr

  | Plus
      (* for [+], given two numbers 
         x + y | 0
       *)
  | Minus
      (* x - y | 0 *)
  | Mul
      (* *)
  | Div
      (* x / y | 0 *)
  | Mod
      (* x  % y *)

(* https://developer.mozilla.org/en-US/docs/Web/JavaScript/Guide/Expressions_and_Operators#Bitwise_operators
    {[
    ~
    ]}
    ~0xff -> -256
    design; make sure each operation type is consistent
 *)
type level = 
  | Log 
  | Info
  | Warn
  | Error

type kind = 
  | Ml
  | Runtime 
  | External of {name : string; default : bool}

type property = Lam_compat.let_kind = 
  | Strict
  | Alias
  | StrictOpt 
  | Variable


type property_name = 
   | Lit of string
   | Symbol_name
  
type 'a access = 
  | Getter
  | Setter
type jsint = Int32.t

type int_or_char = 
    { i : jsint; 
      (* we can not use [int] on 32 bit platform, if we dont use 
          [Int32.t], we need a configuration step          
      *)
      c : char option
    }

 (* literal char *)
type float_lit = { f :  string } [@@unboxed]

type number = 
  | Float of float_lit 
  | Int of int_or_char
  | Uint of int32
  | Nint of nativeint
  (* becareful when constant folding +/-, 
     since we treat it as js nativeint, bitwise operators:
     https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/Bitwise_Operators
     The operands of all bitwise operators are converted to signed 32-bit integers in two's complement format.'
  *)      

type mutable_flag = 
  | Mutable
  | Immutable
  | NA
type direction_flag = 
  | Upto
  | Downto
  | Up

(* 
    {[
    let rec x = 1 :: y 
    and y = 1 :: x
    ]}
 *)
type recursive_info = 
  | SingleRecursive 
  | NonRecursie
  | NA

type used_stats = 
  | Dead_pure 
        (* only [Dead] should be taken serious, 
            other status can be converted during
            inlining
            -- all exported symbols can not be dead
            -- once a symbole is called Dead_pure, 
            it can not be alive anymore, we should avoid iterating it
            
          *)
  | Dead_non_pure 
      (* we still need iterating it, 
         just its bindings does not make sense any more *)
  | Exported (* Once it's exported, shall we change its status anymore? *)
      (* In general, we should count in one pass, and eliminate code in another 
         pass, you can not do it in a single pass, however, some simple 
         dead code can be detected in a single pass
       *)
  | Once_pure (* used only once so that, if we do the inlining, it will be [Dead] *)
  | Used (**)
  | Scanning_pure
  | Scanning_non_pure
  | NA


type ident_info = {
    (* mutable recursive_info : recursive_info; *)
    mutable used_stats : used_stats;
  }

type exports = Ident.t list 




type tag_info = Lam_tag_info.t

type length_object = 
  | Array 
  | String
  | Bytes
  | Function
  | Caml_block

(** TODO: define constant - for better constant folding  *)
(* type constant =  *)
(*   | Const_int of int *)
(*   | Const_ *)