- numerous HashTable performance improvements
        
        This does not quite add up to a measurable win on SunSpider, but it allows a
        follow-on > 3% improvement and probably helps WebCore too.
        
        I made the following improvements, among others:
        
        - Made HashFunctions note whether it is ok to compare a real value with the equal() function
        to the empty or deleted value, and used this to optimize the comparisons done in hash lookup.
        
        - Specialized lookup so it doesn't have to do so many extra branches and build so many extra
        std::pairs for cases that don't need them. There are now four versions, one for read-only access,
        two for writing, and one folded directly into add() (these all were improvments).
        
        - Made HashMap::get() use lookup() directly instead of find() to avoid having to build iterators.
        
        - Made a special constructor for iterators that knows it points to
        a valid filled cell and so skips updating itself.

        - Reordered memory accesses in the various lookup functions for better codegetion
        
        - Made simple translators avoid passing a hash code around
        
        - Other minor tweaks
        
        * wtf/HashTable.h:
        (WTF::):
        (WTF::HashTableConstIterator::HashTableConstIterator):
        (WTF::HashTableIterator::HashTableIterator):
        (WTF::IdentityHashTranslator::translate):
        (WTF::HashTable::end):
        (WTF::HashTable::lookup):
        (WTF::HashTable::lookupForWriting):
        (WTF::HashTable::makeKnownGoodIterator):
        (WTF::HashTable::makeKnownGoodConstIterator):
        (WTF::::lookup):
        (WTF::::lookupForWriting):
        (WTF::::fullLookupForWriting):
        (WTF::::add):
        (WTF::::addPassingHashCode):
        (WTF::::reinsert):
        (WTF::::find):
        (WTF::::contains):
        * kjs/identifier.cpp:
        (WTF::):
        * wtf/HashFunctions.h:
        (WTF::):
        * wtf/HashMap.h:
        (WTF::):
        (WTF::::get):
        * wtf/HashSet.h:
        (WTF::):
        (WTF::::add):
        * wtf/ListHashSet.h:
        (WTF::ListHashSetTranslator::translate):



git-svn-id: http://svn.webkit.org/repository/webkit/trunk@27176 268f45cc-cd09-0410-ab3c-d52691b4dbfc