Optimize Map/Set.prototype.forEach

src/collection.js

 // Copyright 2012 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.
 
 "use strict";
 
 // This file relies on the fact that the following declaration has been made
 // in runtime.js:
 // var $Array = global.Array;
 
@@ skipping 111 matching lines @@
   if (!IS_SET(this)) {
     throw MakeTypeError('incompatible_method_receiver',
                         ['Set.prototype.forEach', this]);
   }
 
   if (!IS_SPEC_FUNCTION(f)) {
     throw MakeTypeError('called_non_callable', [f]);
   }
 
   var iterator = new SetIterator(this, ITERATOR_KIND_VALUES);
-  var entry;
+  var key;
   var stepping = DEBUG_IS_ACTIVE && %DebugCallbackSupportsStepping(f);
-  while (!(entry = %SetIteratorNext(iterator)).done) {
+  var value_array = [UNDEFINED];
+  while (%SetIteratorNext(iterator, value_array)) {
     if (stepping) %DebugPrepareStepInIfStepping(f);
-    %_CallFunction(receiver, entry.value, entry.value, this, f);
+    key = value_array[0];
+    %_CallFunction(receiver, key, key, this, f);
   }
 }
 
 
 // -------------------------------------------------------------------
 
 function SetUpSet() {
   %CheckIsBootstrapping();
 
   %SetCode($Set, SetConstructor);
@@ skipping 110 matching lines @@
   if (!IS_MAP(this)) {
     throw MakeTypeError('incompatible_method_receiver',
                         ['Map.prototype.forEach', this]);
   }
 
   if (!IS_SPEC_FUNCTION(f)) {
     throw MakeTypeError('called_non_callable', [f]);
   }
 
   var iterator = new MapIterator(this, ITERATOR_KIND_ENTRIES);
-  var entry;
   var stepping = DEBUG_IS_ACTIVE && %DebugCallbackSupportsStepping(f);
-  while (!(entry = %MapIteratorNext(iterator)).done) {
+  var value_array = [UNDEFINED, UNDEFINED];
+  while (%MapIteratorNext(iterator, value_array)) {
     if (stepping) %DebugPrepareStepInIfStepping(f);
-    %_CallFunction(receiver, entry.value[1], entry.value[0], this, f);
+    %_CallFunction(receiver, value_array[1], value_array[0], this, f);
   }
 }
 
 
 // -------------------------------------------------------------------
 
 function SetUpMap() {
   %CheckIsBootstrapping();
 
   %SetCode($Map, MapConstructor);
   %FunctionSetPrototype($Map, new $Object());
   %SetProperty($Map.prototype, "constructor", $Map, DONT_ENUM);
 
   %FunctionSetLength(MapForEach, 1);
 
   // Set up the non-enumerable functions on the Map prototype object.
   InstallGetter($Map.prototype, "size", MapGetSizeJS);
   InstallFunctions($Map.prototype, DONT_ENUM, $Array(
     "get", MapGetJS,
     "set", MapSetJS,
     "has", MapHasJS,
     "delete", MapDeleteJS,
     "clear", MapClearJS,
     "forEach", MapForEach
   ));
 }
 
 SetUpMap();