[vectorIntrinsics] RFR: 8265817: Add LoadVectorGather nodes implementation for Arm SVE

[Xiaohong Gong]

On Sun, 25 Apr 2021 08:38:20 GMT, Wang Huang <whuang at openjdk.org> wrote:

>> src/hotspot/cpu/aarch64/aarch64_sve.ad line 4115:
>> 
>>> 4113:   %}
>>> 4114:   ins_pipe(pipe_slow);
>>> 4115: %}
>> 
>> Thanks for your contribution! This patch looks good to me. I just have one question: since currently the SVE supports the vector operations for vector length smaller than the max vector size, does it need to  consider the partial implementation for the `LoadVectorGather `op? Thanks!
>
> Thank you for your review. In my opinion, partial version of `LoadVectorGather` is useful. However, I don't know the plan of `mask`  work of SVE, so I have no plan to implement that now.

Actually this does not strongly depends on the mask feature support for SVE. And we already have the partial implementation that are merged into the panama-vector. I think you can have them as the reference. Thanks!

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PR: https://git.openjdk.java.net/panama-vector/pull/72