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

[Sandhya Viswanathan]

On Tue, 23 Nov 2021 19:01:53 GMT, Jatin Bhateja <jbhateja at openjdk.org> wrote:

>> 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.

@jatin-bhateja On these platforms it is beneficial to set the threshold to zero for copy and clear operations and hence the override. I have described that in the comment in detail as well.

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