Cache length in ElementData::getAttributeItemIndex() for performance

Source/core/dom/ElementData.h

 /*
  * Copyright (C) 2013 Google 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 167 matching lines @@
 inline const Attribute* ElementData::attributeBase() const
 {
     if (m_isUnique)
         return static_cast<const UniqueElementData*>(this)->m_attributeVector.begin();
     return static_cast<const ShareableElementData*>(this)->m_attributeArray;
 }
 
 inline size_t ElementData::getAttributeItemIndex(const QualifiedName& name, bool shouldIgnoreCase) const
 {
     const Attribute* begin = attributeBase();
-    for (unsigned i = 0; i < length(); ++i) {
+    // Cache length for performance as ElementData::length() contains a conditional branch.
+    unsigned len = length();
+    for (unsigned i = 0; i < len; ++i) {
         const Attribute& attribute = begin[i];
         if (attribute.name().matchesPossiblyIgnoringCase(name, shouldIgnoreCase))
             return i;
     }
     return kNotFound;
 }
 
 // We use a boolean parameter instead of calling shouldIgnoreAttributeCase so that the caller
 // can tune the behavior (hasAttribute is case sensitive whereas getAttribute is not).
 inline size_t ElementData::getAttributeItemIndex(const AtomicString& name, bool shouldIgnoreAttributeCase) const
 {
+    // Cache length for performance as ElementData::length() contains a conditional branch.
     unsigned len = length();
     bool doSlowCheck = shouldIgnoreAttributeCase;
 
     // Optimize for the case where the attribute exists and its name exactly matches.
     const Attribute* begin = attributeBase();
     for (unsigned i = 0; i < len; ++i) {
         const Attribute& attribute = begin[i];
         if (!attribute.name().hasPrefix()) {
             if (name == attribute.localName())
                 return i;
@@ skipping 35 matching lines @@
 }
 
 inline Attribute* UniqueElementData::attributeItem(unsigned index)
 {
     return &m_attributeVector.at(index);
 }
 
 } // namespace WebCore
 
 #endif // ElementData_h