[foreign-memaccess+abi] RFR: 8275646: Implement optimized upcall stubs on AArch64 [v2]

[Nick Gasson]

On Mon, 8 Nov 2021 10:46:08 GMT, Andrew Haley <aph at openjdk.org> wrote:

> Tried on MacOS, this is _very_ weird:
> 
> ```
> ....[Hottest Methods (after inlining)]..............................................................
>  25.52%               runtime stub  StubRoutines::updateBytesAdler32 
>```

I think it's a bug in JMH's parsing of the `-XX:+PrintStubCode` output: it's expecting these to all be prefixed with `StubRoutines::` but many aren't including the `optimized_upcall_stub` added by this patch. `StubRoutines::updateBytesAdler32` is the last one printed with that prefix on MacOS, and likewise `StubRoutines::atomic entry points` is the last one printed on Linux (allegedly the third hottest method above). So I think it's been misattributed. I'll see if I can fix it...

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PR: https://git.openjdk.java.net/panama-foreign/pull/610