Add fast path for tag#id selector queries

Source/core/dom/DocumentOrderedMap.cpp

 /*
  * Copyright (C) 2004, 2005, 2006, 2007, 2008, 2009 Apple Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are
  * met:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 62 matching lines @@
     ASSERT(element);
 
     Map::AddResult addResult = m_map.add(key, MapEntry(element));
     if (addResult.isNewEntry)
         return;
 
     MapEntry& entry = addResult.iterator->value;
     ASSERT(entry.count);
     entry.element = 0;
     entry.count++;
+    entry.orderedList.clear();
 }
 
 void DocumentOrderedMap::remove(StringImpl* key, Element* element)
 {
     ASSERT(key);
     ASSERT(element);
 
     Map::iterator it = m_map.find(key);
     if (it == m_map.end())
         return;
 
     MapEntry& entry = it->value;
     ASSERT(entry.count);
     if (entry.count == 1) {
         ASSERT(!entry.element || entry.element == element);
         m_map.remove(it);
     } else {
-        if (entry.element == element)
-            entry.element = 0;
+        if (entry.element == element) {
+            ASSERT(entry.orderedList.isEmpty() || entry.orderedList.first() == element);
+            entry.element = entry.orderedList.size() > 1 ? entry.orderedList[1] : 0;
+        }
         entry.count--;
+        entry.orderedList.clear();
     }
 }
 
 template<bool keyMatches(StringImpl*, Element*)>
 inline Element* DocumentOrderedMap::get(StringImpl* key, const TreeScope* scope) const
 {
     ASSERT(key);
     ASSERT(scope);
 
     Map::iterator it = m_map.find(key);
@@ skipping 14 matching lines @@
     }
     ASSERT_NOT_REACHED();
     return 0;
 }
 
 Element* DocumentOrderedMap::getElementById(StringImpl* key, const TreeScope* scope) const
 {
     return get<keyMatchesId>(key, scope);
 }
 
+const Vector<Element*>& DocumentOrderedMap::getAllElementsById(StringImpl* key, const TreeScope* scope) const
+{
+    ASSERT(key);
+    ASSERT(scope);
+
+    Map::iterator it = m_map.find(key);
+    if (it == m_map.end()) {
+        DEFINE_STATIC_LOCAL(Vector<Element*>, emptyVector, ());

[esprehn, 2013/12/18 00:16:50]

nit: This should be at the top of the function.

[Inactive, 2013/12/18 15:25:56]

Done.

+        return emptyVector;
+    }
+
+    MapEntry& entry = it->value;
+    ASSERT(entry.count);
+
+    if (entry.orderedList.isEmpty()) {
+        entry.orderedList.reserveCapacity(entry.count);
+        for (Element* element = entry.element ? entry.element : ElementTraversal::firstWithin(*scope->rootNode()); entry.orderedList.size() < entry.count; element = ElementTraversal::next(*element)) {
+            ASSERT(element);
+            if (!keyMatchesId(key, element))
+                continue;
+            entry.orderedList.uncheckedAppend(element);
+        }
+        if (!entry.element)
+            entry.element = entry.orderedList.first();
+    }
+
+    return entry.orderedList;
+}
+
 Element* DocumentOrderedMap::getElementByMapName(StringImpl* key, const TreeScope* scope) const
 {
     return get<keyMatchesMapName>(key, scope);
 }
 
 Element* DocumentOrderedMap::getElementByLowercasedMapName(StringImpl* key, const TreeScope* scope) const
 {
     return get<keyMatchesLowercasedMapName>(key, scope);
 }
 
 Element* DocumentOrderedMap::getElementByLabelForAttribute(StringImpl* key, const TreeScope* scope) const
 {
     return get<keyMatchesLabelForAttribute>(key, scope);
 }
 
 } // namespace WebCore