RFR: 8277617: Optimize array copy and clear on x86_64 [v3]

[Jatin Bhateja]

On Tue, 23 Nov 2021 17:52:40 GMT, Sandhya Viswanathan <sviswanathan at openjdk.org> wrote:

>> Currently 32-byte instructions are used for small array copy and clear. 
>> This can be optimized by using 64-byte instructions.
>> 
>> Please review.
>> 
>> Best Regards,
>> Sandhya
>
> Sandhya Viswanathan has updated the pull request incrementally with one additional commit since the last revision:
> 
>   update comment for avx3_threshold() with more details

src/hotspot/cpu/x86/vm_version_x86.hpp line 920:

> 918:   // is set to 0 for these platforms.
> 919:   static int avx3_threshold() { return ((is_intel_family_core() &&
> 920:                                 supports_serialize()) ? 0: AVX3Threshold); }

Hi @sviswa7 , Should we not return a zero threshold only if user does not explicitly set AVX3Threshold i.e. in default case.

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PR: https://git.openjdk.java.net/jdk/pull/6512