Optimize Map/Set.prototype.forEach

src/objects.h

Index: src/objects.h
diff --git a/src/objects.h b/src/objects.h
index c1ba60e972ab35b3c6b72e783a04cf91d099e8c3..11e36412a6e7378115760e8e9a19443da3becbf9 100644
--- a/src/objects.h
+++ b/src/objects.h
@@ -4509,11 +4509,11 @@ class OrderedHashMap:public OrderedHashTable<
       Handle<Object> key,
       Handle<Object> value);
 
- private:
   Object* ValueAt(int entry) {
     return get(EntryToIndex(entry) + kValueOffset);
   }
 
+ private:
   static const int kValueOffset = 1;
 };
 
@@ -10199,8 +10199,22 @@ class OrderedHashTableIterator: public JSObject {
   // end.
   static Handle<JSObject> Next(Handle<Derived> iterator);
 
+  // Whether the iterator has more elements. This needs to be called before
+  // calling |CurrentKey| and/or |CurrentValue|.
+  static bool HasMore(Handle<Derived> iterator);
+
+  // Move the index forward one.
+  static void MoveNext(Handle<Derived> iterator) {
+    iterator->set_index(
+        Smi::FromInt(Smi::cast(iterator->index())->value() + 1));
+  }
+
+  // Returns the current key of the iterator. This should only be called when
+  // |HasMore| returns true.
+  static inline Handle<Object> CurrentKey(Handle<Derived> iterator);
+
  private:
-  // Transitions the iterator to the non obsolote backing store. This is a NOP
+  // Transitions the iterator to the non obsolete backing store. This is a NOP
   // if the [table] is not obsolete.
   void Transition();
 
@@ -10218,9 +10232,10 @@ class JSSetIterator: public OrderedHashTableIterator<JSSetIterator,
   // Casting.
   static inline JSSetIterator* cast(Object* obj);
 
-  static Handle<Object> ValueForKind(
-      Handle<JSSetIterator> iterator,
-      int entry_index);
+  // Returns the iterator result value at the current |index| taking the |kind|
+  // into account. This should only be called when |HasMore| returns true.
+  static Handle<Object> CurrentIteratorResultValue(
+      Handle<JSSetIterator> iterator);
 
  private:
   DISALLOW_IMPLICIT_CONSTRUCTORS(JSSetIterator);
@@ -10237,9 +10252,14 @@ class JSMapIterator: public OrderedHashTableIterator<JSMapIterator,
   // Casting.
   static inline JSMapIterator* cast(Object* obj);
 
-  static Handle<Object> ValueForKind(
-      Handle<JSMapIterator> iterator,
-      int entry_index);
+  // Returns the iterator result value at the current |index| taking the |kind|
+  // into account. This should only be called when |HasMore| returns true.
+  static Handle<Object> CurrentIteratorResultValue(
+      Handle<JSMapIterator> iterator);
+
+  // Returns the current value of the iterator. This should only be called when
+  // |HasMore| returns true.
+  static inline Handle<Object> CurrentValue(Handle<JSMapIterator> iterator);
 
  private:
   DISALLOW_IMPLICIT_CONSTRUCTORS(JSMapIterator);