RFR: 8307352: AARCH64: Improve itable_stub

[Andrew Haley]

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.

Efficient systems are made from thousands of tiny optimizations, and few of them on their own are large enough to make a measurable difference to performance. So it is for vehicles, so it is for computers.

Having said that, I'd probably be opposed to anything in this area that made for more code or added complexity.

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PR Review Comment: https://git.openjdk.org/jdk/pull/13792#discussion_r1236583792