https://bugs.webkit.org/show_bug.cgi?id=121056

Reviewed by Geoffrey Garen.

Added localToOperand(), operandToLocal() and operandIsLocal() to Operands.h, very similar to
argumentToOperand(), et al.  Used the new helpers everywhere where an index into a data
structure is intended instead of the actual virtual register offset.  When the stack is
changed to grow down, local register offsets can be negative.  Also added the helper
DFG::SpeculativeJIT::generationInfoFromVirtualRegister() for the common case accessing 
m_generationInfo[operandToLocal(val)].

* bytecode/CodeBlock.cpp:
* bytecode/CodeBlock.h:
* bytecode/Operands.h:
(JSC::localToOperand):
(JSC::operandIsLocal):
(JSC::operandToLocal):
* bytecompiler/BytecodeGenerator.h:
* dfg/DFGAbstractInterpreterInlines.h:
* dfg/DFGByteCodeParser.cpp:
* dfg/DFGCFGSimplificationPhase.cpp:
* dfg/DFGCPSRethreadingPhase.cpp:
* dfg/DFGOSREntry.cpp:
* dfg/DFGOSRExitCompiler32_64.cpp:
* dfg/DFGOSRExitCompiler64.cpp:
* dfg/DFGScoreBoard.h:
* dfg/DFGSpeculativeJIT.cpp:
* dfg/DFGSpeculativeJIT.h:
(JSC::DFG::SpeculativeJIT::generationInfoFromVirtualRegister):
* dfg/DFGSpeculativeJIT32_64.cpp:
* dfg/DFGSpeculativeJIT64.cpp:
* dfg/DFGValidate.cpp:
* dfg/DFGVariableEventStream.cpp:
* dfg/DFGVirtualRegisterAllocationPhase.cpp:
* jit/JITInlines.h:
* jit/JITOpcodes.cpp:
* jit/JITOpcodes32_64.cpp:


git-svn-id: http://svn.webkit.org/repository/webkit/trunk@155415 268f45cc-cd09-0410-ab3c-d52691b4dbfc