Changeset 27176 in webkit for trunk/JavaScriptCore/kjs/identifier.cpp

Timestamp:

Oct 28, 2007, 1:17:39 AM (18 years ago)

Author:

mjs

Message:

Reviewed by Oliver.

• 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):

File:

• trunk/JavaScriptCore/kjs/identifier.cpp (modified) (1 diff)

trunk/JavaScriptCore/kjs/identifier.cpp

@@ -39 +39 @@
         static unsigned hash(const KJS::UString::Rep *key) { return key->hash(); }
         static bool equal(const KJS::UString::Rep *a, const KJS::UString::Rep *b) { return KJS::Identifier::equal(a, b); }
+        static const bool safeToCompareToEmptyOrDeleted = false;
     };