RFR: 8307352: AARCH64: Improve itable_stub [v2]

[Evgeny Astigeevich]

On Tue, 20 Jun 2023 13:34:45 GMT, Boris Ulasevich <bulasevich at openjdk.org> wrote:

>>> Yes, there are similar calls to lookup_interface_method stubs from TemplateTable::invokeinterface and from VtableStubs::create_itable_stub. Unfortunately, the instructions in between the lookup_interface_method calls are different, making it difficult to create a common stub for them. Performance is not an issue for the interpreter.
>> 
>> Really? if performance were not an issue for the interpreter we'd all use the C++ interpreter.
>
> What I am trying to say is that I have not found any benchmark or application where a performance impact of TemplateTable::invokeinterface is visible. I would be happy to rework it as well once we see a benchmark which clearly demonstrates the gain, and the gain is substantial to justify the code complexity.

@bulasevich 
> What I am trying to say is that I have not found any benchmark

IMHO you can run the benchmark mentioned in the description with `-Xint`.

> Unfortunately, the instructions in between the lookup_interface_method calls are different, making it difficult to create a common stub for them.

If it needs a lot of work, we can create a JBS issue to implement the same approach for the interpreter. When it is being implemented some common parts might be identified and refactored.

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PR Review Comment: https://git.openjdk.org/jdk/pull/13792#discussion_r1258115516