RFR: 8186670: Implement _onSpinWait() intrinsic for AArch64 [v10]

[Evgeny Astigeevich]

On Fri, 15 Oct 2021 13:09:27 GMT, Andrew Haley <aph at openjdk.org> wrote:

> > @theRealAph, any comments on the microbenchmark I wrote?
> 
> Something like this works well:

Thank you for the microbenchmark. I added it.
I also added a microbenchmark to measure the latency of `Thread.onSpinWait` vs `Thread.sleep(0)` vs no pause.
And a microbenchmark `ThreadOnSpinWaitProducerConsumer`.

-------------

PR: https://git.openjdk.java.net/jdk/pull/5562