https://bugs.webkit.org/show_bug.cgi?id=90146

Reviewed by Oliver Hunt.
        
This removes a bunch of code that was previously trying to prevent spurious
reoptimizations if a large enough majority of executions of a code block did
not result in OSR exit. It turns out that this code was purely harmful. This
patch removes all of that logic and replaces it with a dead-simple
heuristic: if you exit more than N times (where N is an exponential function
of the number of times the code block has already been recompiled) then we
will recompile.
        
This appears to be a broad ~1% win on many benchmarks large and small.

* bytecode/CodeBlock.cpp:
(JSC::CodeBlock::CodeBlock):
* bytecode/CodeBlock.h:
(JSC::CodeBlock::osrExitCounter):
(JSC::CodeBlock::countOSRExit):
(CodeBlock):
(JSC::CodeBlock::addressOfOSRExitCounter):
(JSC::CodeBlock::offsetOfOSRExitCounter):
(JSC::CodeBlock::adjustedExitCountThreshold):
(JSC::CodeBlock::exitCountThresholdForReoptimization):
(JSC::CodeBlock::exitCountThresholdForReoptimizationFromLoop):
(JSC::CodeBlock::shouldReoptimizeNow):
(JSC::CodeBlock::shouldReoptimizeFromLoopNow):
* bytecode/ExecutionCounter.cpp:
(JSC::ExecutionCounter::setThreshold):
* bytecode/ExecutionCounter.h:
(ExecutionCounter):
(JSC::ExecutionCounter::clippedThreshold):
* dfg/DFGJITCompiler.cpp:
(JSC::DFG::JITCompiler::compileBody):
* dfg/DFGOSRExit.cpp:
(JSC::DFG::OSRExit::considerAddingAsFrequentExitSiteSlow):
* dfg/DFGOSRExitCompiler.cpp:
(JSC::DFG::OSRExitCompiler::handleExitCounts):
* dfg/DFGOperations.cpp:
* jit/JITStubs.cpp:
(JSC::DEFINE_STUB_FUNCTION):
* runtime/Options.cpp:
(Options):
(JSC::Options::initializeOptions):
* runtime/Options.h:
(Options):



git-svn-id: http://svn.webkit.org/repository/webkit/trunk@121511 268f45cc-cd09-0410-ab3c-d52691b4dbfc