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

[Volker Simonis]

On Fri, 20 Nov 2020 16:16:19 GMT, Volker Simonis <simonis at openjdk.org> wrote:

>> This commit adds detection for Graviton 1 (as Cortex-A72) and for Graviton 2 (as Neoverse N1) and enables UseSIMDForMemoryOps for them.
>> 
>> The patch passed jtreg tier1-2 and all gtest tests with linux-aarch64-server-release build.
>
> 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

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