[vectorIntrinsics+mask] RFR: 8267368: Add masking support for reduction vector intrinsics

[Xiaohong Gong]

On Mon, 24 May 2021 06:15:56 GMT, Xiaohong Gong <xgong at openjdk.org> wrote:

> This patch adds the masking support for vector reduction operations, including the Vector API java implementation and hotspot intrinsics changes. It adds the mask information to the reduction intrinsic method. With it:
>   - Both masked and non-masked reduction operations call the same hotspot intrinsics. The mask value and class are set to `"null"` for non-masked operations.
>   - Reduction IR with mask as another input will be generated if the platform supports the predicate feature for the op. Otherwise, the vector blend pattern will be generated like before.
> 
> Note that this patch only contains the Vector API java implementation and the hotspot intrinsics changes. No compiler mid-end and backend implementations are included.

Hi @iwanowww, may I have your kindly feedback to the compiler side for this PR please? Thanks so much!

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PR: https://git.openjdk.java.net/panama-vector/pull/86