RFR: 8253049: Enhance itable_stub for AArch64 and x86_64

[Vladimir Ivanov]

>> And speaking of the overall approach (as it is implemented now), IMO
>> increased complexity doesn't worth it. If interface calls become a
>> bottleneck, the problem lies not in itable stub, but the overall design
>> which requires linear scan over itables. It's better to put the effort
>> there than micro-optimizing the stub.
> 
> Indeed. When I first came to HotSpot after working on GCJ for years
> I was very surprised to see a linear scan used for interface dispatch.

FTR ErikÖ has been looking into rewriting virtual dispatch logic:

   http://openjdk.java.net/jeps/8221828

Best regards,
Vladimir Ivanov

> 
> The code improvements look to be fairly minor.
>