RFR: 8255351: Add detection for Graviton 2 CPUs [v2]

[Evgeny Astigeevich]

On Mon, 23 Nov 2020 23:37:44 GMT, Vladimir Kozlov <kvn at openjdk.org> wrote:

>> Evgeny Astigeevich has refreshed the contents of this pull request, and previous commits have been removed. The incremental views will show differences compared to the previous content of the PR. The pull request contains one new commit since the last revision:
>> 
>>   8255351: Add detection for Graviton 2 CPUs
>>   
>>   This commit adds detection for Graviton 2 (as Neoverse N1)
>>   and enables UseSIMDForMemoryOps for it.
>
> Marked as reviewed by kvn (Reviewer).

I've got additional performance data. It shows that Graviton 1 has different behaviour regarding SIMD for memory ops than Graviton 2. Especially array lengths, when it is worth to use SIMD instructions. We will address the issues in a separate PR.

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