[jdk17u-dev] RFR: 8321025: Enable Neoverse N1 optimizations for Neoverse V2

[Aleksey Shipilev]

On Fri, 14 Jun 2024 00:22:06 GMT, Xiaolong Peng <xpeng at openjdk.org> wrote:

> ### Notes
> 
> Backport 8321025: Enable Neoverse N1 optimizations for Neoverse V2  to jdk17, it is not a clean backport, the method ```model_is(0xd40) ``` is in jdk17, equivalent code in jdk17 is like ```(_model == 0xd40 || _model2 == 0xd40)```. 
> 
> ### Verification
> Not able to test it on CPU with Neoverse V2, I don't have server supports Neoverse V2 yet, but the code has been backported to [Amazon Corretto 17](https://github.com/corretto/corretto-17/blob/release-17.0.11.9.1/CHANGELOG.md) since January 16, 2024, overall it should be a low risk.

In Corretto 17, we picked up `is_model`: https://github.com/corretto/corretto-17/commit/3d11b555446102e07bcaf60d077364d499bc82a5. Seeing how this backport is already not clean, I think we should do the same here. It would also provide a bit more credence to the patch, as we propose exactly the same patch that already runs in prod.

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PR Comment: https://git.openjdk.org/jdk17u-dev/pull/2579#issuecomment-2173714116