RFR: 8255351: Add detection for Graviton 1 & 2 CPUs

[Eugene Astigeevich]

On Fri, 20 Nov 2020 16:47:01 GMT, Volker Simonis <simonis at openjdk.org> wrote:

>> Evgeny works for the Amazon Corretto team and is covered by the Amazon OCA.
>
> Hi Evegeny,
> 
> in general, your changes look good to me.
> 
> You've disabled SIMD instructions for copying byte arrays <= 96 because you say there are no benefits from using them.
> Have you seen regression in the microbenchmarks? As far as I can see, you've only pasted the results for char, int and long (where the improvements are quite nice, by the way :)
> 
> Could you please also post some results for byte arrays (with and without SIMD).
> 
> Thank you and best regards,
> Volker

I work for the Amazon Corretto team and am covered by the Amazon OCA. See the [comment](https://github.com/openjdk/jdk/pull/1315#issuecomment-731262807) from Volker above.

> Hi Evegeny,
> 
> in general, your changes look good to me.
> 
> You've disabled SIMD instructions for copying byte arrays <= 96 because you say there are no benefits from using them.
> Have you seen regression in the microbenchmarks? As far as I can see, you've only pasted the results for char, int and long (where the improvements are quite nice, by the way :)
> 
> Could you please also post some results for byte arrays (with and without SIMD).
> 
> Thank you and best regards,
> Volker

Thank you, Volker.
I did more runs of testByte microbenchmarks with PR https://github.com/openjdk/jdk/pull/1293. They show that only ArrayCopyUnalignedDst.testByte has some regressions. I am running full range of copying from 65 to 96 to see which are more affected.
I decided to enable UseSIMDForMemoryOps for all types of copying because overall it with PR https://github.com/openjdk/jdk/pull/1293 brings good improvements. I'll address ArrayCopyUnalignedDst.testByte regressions in a separate PR.

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PR: https://git.openjdk.java.net/jdk/pull/1315