https://bugs.webkit.org/show_bug.cgi?id=64147

Patch by Filip Pizlo <fpizlo@apple.com> on 2011-07-13
Reviewed by Gavin Barraclough.

This implements unified support for prototype caching, prototype chain
caching, and polymorphic (i.e. list) prototype and prototype chain
caching.  This is done by creating common code for emitting prototype
or chain access stubs, and having it factored out into
generateProtoChainAccessStub().  This function is called by
tryCacheGetByID once the latter determines that some form of prototype
access caching is necessary (i.e. the slot being accessed is not on the
base value but on some other object).

Direct prototype list, and prototype chain list, caching is implemented by
linking the slow path to operationGetByIdProtoBuildList(), which uses the
same helper function (generateProtoChainAccessStub()) as tryCacheGetByID.

This change required ensuring that the value in the scratchGPR field in
StructureStubInfo is preserved even after the stub info is in the
chain, or proto_list, states.  Hence scratchGPR was moved out of the union
and into the top-level of StructureStubInfo.

* bytecode/StructureStubInfo.h:
* dfg/DFGJITCompiler.cpp:
(JSC::DFG::JITCompiler::compileFunction):
* dfg/DFGOperations.cpp:
* dfg/DFGOperations.h:
* dfg/DFGRepatch.cpp:
(JSC::DFG::emitRestoreScratch):
(JSC::DFG::linkRestoreScratch):
(JSC::DFG::generateProtoChainAccessStub):
(JSC::DFG::tryCacheGetByID):
(JSC::DFG::tryBuildGetByIDProtoList):
(JSC::DFG::dfgBuildGetByIDProtoList):
(JSC::DFG::tryCachePutByID):
* dfg/DFGRepatch.h:

git-svn-id: http://svn.webkit.org/repository/webkit/trunk@90950 268f45cc-cd09-0410-ab3c-d52691b4dbfc