VarHandle MethodType lookup table not needed for OJDK MH

[babsingh]

VarHandle MethodType lookup table is stored in the J9ROMClass.

The code related to the VarHandle MethodType lookup table should be wrapped with J9VM_OPT_METHOD_HANDLE or an identical flag so that it stays disabled for OJDK MH.

The code related to the VarHandle MethodType lookup table is mentioned in the following comments:

1. Remove dead/unreferenced data in ROMClasses #11566 (review)
2. Remove dead/unreferenced data in ROMClasses #11566 (comment)

[babsingh]

fyi @DanHeidinga @fengxue-IS @tajila
This issue needs to be tagged with project:MH.

[EricYangIBM]

I am unsure what to do for https://github.com/eclipse-openj9/openj9/blob/master/runtime/compiler/optimizer/VarHandleTransformer.cpp#L295. That method is accessing the varhandlemethodtypelookuptable so I think some changes are necessary when ojdk method handles are enabled.

Same for lookupVarHandleMethodTypeCacheIndex: https://github.com/eclipse-openj9/openj9/blob/master/runtime/codert_vm/cnathelp.cpp#L2496

[fengxue-IS]

The first link code should be never used with ojdk MH enabled, so you should be able to ifdef the code block with J9VM_OPT_METHOD_HANDLE.
@nbhuiyan can you confirm that VarHandleTransformer functions are not used with ojdk MH, and if it is possible to ifdef them out when ojdk mh is enabled

for second link, you don't need to do anything as the code is already ifdef with J9VM_OPT_OPENJDK_METHODHANDLE

[nbhuiyan]

Yes, this is not used with ojdk MHs. We can safely ifdef out the entire body of TR_VarHandleTransformer::perform() (except return 0) in ojdk MH builds.