[builtins] Improve performance of array.prototype.filter and map

src/js/typedarray.js

 // Copyright 2013 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 (function(global, utils) {
 
 "use strict";
 
 %CheckIsBootstrapping();
 
 // -------------------------------------------------------------------
 // Imports
 
 // array.js has to come before typedarray.js for this to work
 var ArrayToString = utils.ImportNow("ArrayToString");
 var ArrayValues;
 var GetIterator;
 var GetMethod;
 var GlobalArray = global.Array;
 var GlobalArrayBuffer = global.ArrayBuffer;
 var GlobalArrayBufferPrototype = GlobalArrayBuffer.prototype;
 var GlobalObject = global.Object;
-var InnerArrayFilter;
 var InnerArrayFind;
 var InnerArrayFindIndex;
 var InnerArrayJoin;
 var InnerArraySort;
 var InnerArrayToLocaleString;
 var InternalArray = utils.InternalArray;
 var MaxSimple;
 var MinSimple;
 var SpeciesConstructor;
 var ToPositiveInteger;
@@ skipping 18 matching lines @@
 endmacro
 
 TYPED_ARRAYS(DECLARE_GLOBALS)
 
 var GlobalTypedArray = %object_get_prototype_of(GlobalUint8Array);
 
 utils.Import(function(from) {
   ArrayValues = from.ArrayValues;
   GetIterator = from.GetIterator;
   GetMethod = from.GetMethod;
-  InnerArrayFilter = from.InnerArrayFilter;
   InnerArrayFind = from.InnerArrayFind;
   InnerArrayFindIndex = from.InnerArrayFindIndex;
   InnerArrayJoin = from.InnerArrayJoin;
   InnerArraySort = from.InnerArraySort;
   InnerArrayToLocaleString = from.InnerArrayToLocaleString;
   MaxSimple = from.MaxSimple;
   MinSimple = from.MinSimple;
   SpeciesConstructor = from.SpeciesConstructor;
   ToPositiveInteger = from.ToPositiveInteger;
   ToIndex = from.ToIndex;
@@ skipping 319 matching lines @@
 // ES6 draft 08-24-14, section 22.2.3.12
 function TypedArrayForEach(f, receiver) {
   if (!IS_TYPEDARRAY(this)) throw %make_type_error(kNotTypedArray);
 
   var length = %_TypedArrayGetLength(this);
 
   InnerTypedArrayForEach(f, receiver, this, length);
 }
 %FunctionSetLength(TypedArrayForEach, 1);
 
+// The following functions cannot be made efficient on sparse arrays while
+// preserving the semantics, since the calls to the receiver function can add
+// or delete elements from the array.
+function InnerTypedArrayFilter(f, receiver, array, length, result) {
+  var result_length = 0;
+  for (var i = 0; i < length; i++) {
+    if (i in array) {
+      var element = array[i];
+      if (%_Call(f, receiver, element, i, array)) {
+        %CreateDataProperty(result, result_length, element);
+        result_length++;
+      }
+    }
+  }
+  return result;
+}
+
 
 // ES6 draft 07-15-13, section 22.2.3.9
 function TypedArrayFilter(f, thisArg) {
   if (!IS_TYPEDARRAY(this)) throw %make_type_error(kNotTypedArray);
 
   var length = %_TypedArrayGetLength(this);
   if (!IS_CALLABLE(f)) throw %make_type_error(kCalledNonCallable, f);
   var result = new InternalArray();
-  InnerArrayFilter(f, thisArg, this, length, result);
+  InnerTypedArrayFilter(f, thisArg, this, length, result);
   var captured = result.length;
   var output = TypedArraySpeciesCreate(this, captured);
   for (var i = 0; i < captured; i++) {
     output[i] = result[i];
   }
   return output;
 }
 %FunctionSetLength(TypedArrayFilter, 1);
 
 
@@ skipping 268 matching lines @@
   %AddNamedProperty(GlobalNAME.prototype,
                     "constructor", global.NAME, DONT_ENUM);
   %AddNamedProperty(GlobalNAME.prototype,
                     "BYTES_PER_ELEMENT", ELEMENT_SIZE,
                     READ_ONLY | DONT_ENUM | DONT_DELETE);
 endmacro
 
 TYPED_ARRAYS(SETUP_TYPED_ARRAY)
 
 })