https://bugs.webkit.org/show_bug.cgi?id=110674

Reviewed by Sam Weinig.

Deployed the idiomatic "add null value" trick to avoid a second hash
lookup when inserting an item.

* runtime/CodeCache.cpp:
(JSC::CodeCacheMap::pruneSlowCase): Factored this into a helper function
to improve clarity and get some code off the hot path.

(JSC::CodeCache::getCodeBlock):
(JSC::CodeCache::getFunctionExecutableFromGlobalCode): Use the add() API
to avoid two hash lookups. Be sure to remove items if parsing fails,
otherwise we'll leave nulls in the table. (I'm guessing that caching parse
errors is not a win.)

* runtime/CodeCache.h:
(JSC::SourceCodeValue::SourceCodeValue):
(CodeCacheMap):
(JSC::CodeCacheMap::add): Combined find() and set() into add().

(JSC::CodeCacheMap::remove):
(JSC::CodeCacheMap::age):
(JSC::CodeCacheMap::prune): Refactored to support above changes.


git-svn-id: http://svn.webkit.org/repository/webkit/trunk@143949 268f45cc-cd09-0410-ab3c-d52691b4dbfc