RFR: 8277617: Adjust AVX3Threshold for copy/fill stubs

[Nils Eliasson]

On Wed, 1 Dec 2021 07:08:33 GMT, Jie Fu <jiefu at openjdk.org> wrote:

> 
> We don't use the 64-byte instructions as default on Intel's old AVX512 platforms, right? If so, is it possible a performance regression for the old platforms after this patch? Thanks.

As I understand it - old AVX512 platforms will continue to work as before. The new case is that new platforms (that have avx_threshold set to 0) will use 64 byte instructions. But it would be nice with some benchmarks that verify that there are no regression on old avx512 hardware.

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