https://bugs.webkit.org/show_bug.cgi?id=116630

Reviewed by Mark Hahnenberg.

This gives us the ability to use more compiler threads, but doesn't actually
enable the functionality because it isn't a speed-up on any benchmark. It can
even be a slow-down. This also adds the ability to disable concurrent
compilation if we're on a uniprocessor machine, and adds more logging to the
worklist code to allow us to investigate how many threads are active. It
appears that even on the most compiler-heavy benchmarks, we never have enough
work for more than 4 threads, and even then the 4 threads are all active for
a short time.

Something that having more threads does accomplish is that it shakes out bugs.
This patch fixes a bug with Watchpoint not being thread-safe ref-counted,
which enabling 7 compilation threads did catch.

As it stands, this patch is performance-neutral and just fixes bugs and adds
some options.

* bytecode/Watchpoint.h:
* dfg/DFGCommon.h:
(JSC::DFG::enableConcurrentJIT):
* dfg/DFGWorklist.cpp:
(JSC::DFG::Worklist::Worklist):
(JSC::DFG::Worklist::~Worklist):
(JSC::DFG::Worklist::finishCreation):
(JSC::DFG::Worklist::create):
(JSC::DFG::Worklist::enqueue):
(JSC::DFG::Worklist::waitUntilAllPlansForVMAreReady):
(JSC::DFG::Worklist::dump):
(JSC::DFG::Worklist::runThread):
(JSC::DFG::initializeGlobalWorklistOnce):
* dfg/DFGWorklist.h:
* runtime/Options.cpp:
(JSC::computeNumberOfWorkerThreads):
(JSC):
(JSC::computeNumberOfGCMarkers):
* runtime/Options.h:
(JSC):

git-svn-id: http://svn.webkit.org/repository/webkit/trunk@153175 268f45cc-cd09-0410-ab3c-d52691b4dbfc