RFR: 8367478: Improve UseAVX setting and add cpu descriptions for zhaoxin processors [v3]

[Vic Wang]

On Mon, 5 Jan 2026 09:09:47 GMT, Jie Fu <jiefu at openjdk.org> wrote:

> > The performance improvement from this change is not significant.
> 
> If no obvious performance improvement, why change it? Are you sure there is no performance degradation after this change?

We have tested this change using benchmarks such as SPECjvm and SPECpower. While there is no obvious performance improvement (the gain is within ~0.5%), there is also no performance degradation.

The primary goal of this patch is to improve how UseAVX is configured across different platforms and to provide a better foundation for future products. Previously, the code did not distinguish between older and newer platforms and effectively defaulted to setting UseAVX=0 for all products, which is clearly not ideal.

Therefore, we hope to improve the code logic for UseAVX. 
Thanks for the review.

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PR Comment: https://git.openjdk.org/jdk/pull/27241#issuecomment-3709863284