profiles
https://bugs.webkit.org/show_bug.cgi?id=68677

Reviewed by Oliver Hunt.
        
This adds the ForceOSRExit node, which is ignored by the propagator
and virtual register allocator (and hence ensuring that liveness analysis
works correctly), but forces terminateSpeculativeExecution() in the
back-end. This appears to be a slight speed-up on benchmark averages,
with ~5% swings on individual benchmarks, in both directions. But it's
never a regression on any average, and appears to be a ~1% progression
in the SunSpider average.
        
This also adds a bit better debugging support in the old JIT and in DFG,
as this was necessary to debug the much more frequent OSR transitions
that occur with this change.

* dfg/DFGByteCodeParser.cpp:
(JSC::DFG::ByteCodeParser::addCall):
(JSC::DFG::ByteCodeParser::getStrongPrediction):
(JSC::DFG::ByteCodeParser::parseBlock):
* dfg/DFGJITCompiler.cpp:
(JSC::DFG::JITCompiler::exitSpeculativeWithOSR):
* dfg/DFGNode.h:
* dfg/DFGPropagator.cpp:
(JSC::DFG::Propagator::propagateNodePredictions):
* dfg/DFGSpeculativeJIT.cpp:
(JSC::DFG::SpeculativeJIT::compile):
* jit/JIT.cpp:
(JSC::JIT::privateCompileMainPass):
(JSC::JIT::privateCompileSlowCases):
(JSC::JIT::privateCompile):
* jit/JIT.h:



git-svn-id: http://svn.webkit.org/repository/webkit/trunk@95916 268f45cc-cd09-0410-ab3c-d52691b4dbfc