Bring back fast paths for HTMLTagCollection / ClassCollection's access

Source/core/html/HTMLCollection.cpp

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  *           (C) 1999 Antti Koivisto (koivisto@kde.org)
  * Copyright (C) 2003, 2004, 2005, 2006, 2007, 2008, 2011, 2012 Apple Inc. All rights reserved.
  *
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Library General Public
  * License as published by the Free Software Foundation; either
  * version 2 of the License, or (at your option) any later version.
  *
@@ skipping 251 matching lines @@
     case ChildNodeListType:
     case NameNodeListType:
     case RadioNodeListType:
     case RadioImgNodeListType:
     case LabelsNodeListType:
         ASSERT_NOT_REACHED();
     }
     return false;
 }
 
+template <> inline bool isMatchingElement(const ClassCollection& collection, const Element& element)
+{
+    return collection.elementMatches(element);
+}
+
+template <> inline bool isMatchingElement(const HTMLTagCollection& collection, const Element& element)
+{
+    return collection.elementMatches(element);
+}
+
 template <> inline bool isMatchingElement(const LiveNodeList& nodeList, const Element& element)
 {
     return nodeList.nodeMatches(element);
 }
 
 static Node* previousNode(const Node& base, const Node& previous, bool onlyIncludeDirectChildren)
 {
     return onlyIncludeDirectChildren ? previous.previousSibling() : NodeTraversal::previous(previous, &base);
 }
 
@@ skipping 153 matching lines @@
 {
     Element* next = &current;
     do {
         next = ElementTraversal::nextSkippingChildren(*next, &root);
     } while (next && !isMatchingElement(nodeList, *next));
     return next;
 }
 
 Element* HTMLCollection::traverseToFirstElement(const ContainerNode& root) const
 {
-    if (overridesItemAfter())
-        return virtualItemAfter(0);
-    if (shouldOnlyIncludeDirectChildren())
-        return firstMatchingChildElement(*this, root);
-    return firstMatchingElement(*this, root);
+    switch (type()) {

[arv (Not doing code reviews), 2014/02/04 15:12:36]

Would it make sense to use virtual dispatch instead of switch?

[Inactive, 2014/02/04 15:30:15]

As this is hot code, I think we should avoid virtual calls. A switch is what was
used before my CL that caused the regression so I am merely bringing it back.

+    case HTMLTagCollectionType:
+        return firstMatchingElement(static_cast<const HTMLTagCollection&>(*this), root);
+    case ClassCollectionType:
+        return firstMatchingElement(static_cast<const ClassCollection&>(*this), root);
+    default:
+        if (overridesItemAfter())
+            return virtualItemAfter(0);
+        if (shouldOnlyIncludeDirectChildren())
+            return firstMatchingChildElement(*this, root);
+        return firstMatchingElement(*this, root);
+    }
 }
 
 inline Element* HTMLCollection::traverseNextElement(Element& previous, const ContainerNode& root) const
 {
     if (overridesItemAfter())
         return virtualItemAfter(&previous);
     if (shouldOnlyIncludeDirectChildren())
         return nextMatchingChildElement(*this, previous, root);
     return nextMatchingElement(*this, previous, root);
 }
 
 Element* HTMLCollection::traverseForwardToOffset(unsigned offset, Node& currentElement, unsigned& currentOffset, const ContainerNode& root) const
 {
     ASSERT(currentOffset < offset);
-    if (overridesItemAfter()) {
-        Element* next = &toElement(currentElement);
-        while ((next = virtualItemAfter(next))) {
-            if (++currentOffset == offset)
-                return next;
+    switch (type()) {
+    case HTMLTagCollectionType:
+        return traverseMatchingElementsForwardToOffset(static_cast<const HTMLTagCollection&>(*this), offset, toElement(currentElement), currentOffset, root);
+    case ClassCollectionType:
+        return traverseMatchingElementsForwardToOffset(static_cast<const ClassCollection&>(*this), offset, toElement(currentElement), currentOffset, root);
+    default:
+        if (overridesItemAfter()) {
+            Element* next = &toElement(currentElement);
+            while ((next = virtualItemAfter(next))) {
+                if (++currentOffset == offset)
+                    return next;
+            }
+            return 0;
         }
-        return 0;
+        if (shouldOnlyIncludeDirectChildren()) {
+            Element* next = &toElement(currentElement);
+            while ((next = nextMatchingChildElement(*this, *next, root))) {
+                if (++currentOffset == offset)
+                    return next;
+            }
+            return 0;
+        }
+        return traverseMatchingElementsForwardToOffset(*this, offset, toElement(currentElement), currentOffset, root);
     }
-    if (shouldOnlyIncludeDirectChildren()) {
-        Element* next = &toElement(currentElement);
-        while ((next = nextMatchingChildElement(*this, *next, root))) {
-            if (++currentOffset == offset)
-                return next;
-        }
-        return 0;
-    }
-    return traverseMatchingElementsForwardToOffset(*this, offset, toElement(currentElement), currentOffset, root);
 }
 
 Element* HTMLCollection::namedItem(const AtomicString& name) const
 {
     // http://msdn.microsoft.com/workshop/author/dhtml/reference/methods/nameditem.asp
     // This method first searches for an object with a matching id
     // attribute. If a match is not found, the method then searches for an
     // object with a matching name attribute, but only on those elements
     // that are allowed a name attribute.
 
@@ skipping 59 matching lines @@
 
 void HTMLCollection::append(NodeCacheMap& map, const AtomicString& key, Element* element)
 {
     OwnPtr<Vector<Element*> >& vector = map.add(key.impl(), nullptr).iterator->value;
     if (!vector)
         vector = adoptPtr(new Vector<Element*>);
     vector->append(element);
 }
 
 } // namespace WebCore