Optimize op_call by allowing call sites to be directly linked to callees.

        For the hot path of op_call, CTI now generates a check (initially for an impossible
        value), and the first time the call is executed we attempt to link the call directly
        to the callee.  WWe can currently only do so if the arity of the caller and callee
        match.  The (optimized) setup for the call on the hot path is linked directly to
        the ctiCode for the callee, without indirection.
        
        Two forms of the slow case of the call are generated, the first will be executed the
        first time the call is reached.  As well as this path attempting to link the call to
        a callee, it also relinks the slow case to a second slow case, which will not continue
        to attempt relinking the call.  (This policy could be changed in future, but for not
        this is intended to prevent thrashing).

        If a callee that the caller has been linked to is garbage collected, then the link
        in the caller's JIt code will be reset back to a value that cannot match - to prevent
        any false positive matches.

        ~20% progression on deltablue & richards, >12% overall reduction in v8-tests
        runtime, one or two percent progression on sunspider.

        Reviewed by Oliver Hunt.

        * VM/CTI.cpp:
        (JSC::):
        (JSC::CTI::emitNakedCall):
        (JSC::unreachable):
        (JSC::CTI::compileOpCallInitializeCallFrame):
        (JSC::CTI::compileOpCallSetupArgs):
        (JSC::CTI::compileOpCall):
        (JSC::CTI::privateCompileMainPass):
        (JSC::CTI::privateCompileSlowCases):
        (JSC::CTI::privateCompile):
        (JSC::CTI::unlinkCall):
        (JSC::CTI::linkCall):
        * VM/CTI.h:
        * VM/CodeBlock.cpp:
        (JSC::CodeBlock::~CodeBlock):
        (JSC::CodeBlock::unlinkCallers):
        (JSC::CodeBlock::derefStructureIDs):
        * VM/CodeBlock.h:
        (JSC::StructureStubInfo::StructureStubInfo):
        (JSC::CallLinkInfo::CallLinkInfo):
        (JSC::CodeBlock::addCaller):
        (JSC::CodeBlock::removeCaller):
        (JSC::CodeBlock::getStubInfo):
        * VM/CodeGenerator.cpp:
        (JSC::CodeGenerator::emitCall):
        (JSC::CodeGenerator::emitConstruct):
        * VM/Machine.cpp:
        (JSC::Machine::cti_op_call_profiler):
        (JSC::Machine::cti_op_call_JSFunction):
        (JSC::Machine::cti_vm_lazyLinkCall):
        (JSC::Machine::cti_op_construct_JSConstructFast):
        (JSC::Machine::cti_op_construct_JSConstruct):
        (JSC::Machine::cti_op_construct_NotJSConstruct):
        * VM/Machine.h:
        * kjs/JSFunction.cpp:
        (JSC::JSFunction::~JSFunction):
        * kjs/JSFunction.h:
        * kjs/nodes.h:
        (JSC::FunctionBodyNode::):
        * masm/X86Assembler.h:
        (JSC::X86Assembler::getDifferenceBetweenLabels):



git-svn-id: http://svn.webkit.org/repository/webkit/trunk@37670 268f45cc-cd09-0410-ab3c-d52691b4dbfc