[vectorIntrinsics] RFR: 8263644: Add Extract float nodes implementation for Arm SVE

[Xiaohong Gong]

On Wed, 17 Mar 2021 01:29:47 GMT, Wang Huang <whuang at openjdk.org> wrote:

> We implement ExtractD & ExtractF Node for Arm SVE backend.
> * overload encoding functions `sve_lasta` & `sve_lastb`
> * for future JDK-8263424, we eliminate vector length judgements and use  `rscratch1`

src/hotspot/cpu/aarch64/aarch64_sve.ad line 3088:

> 3086:   format %{ "movzw rscratch1, $idx\n\t"
> 3087:             "sve_whilele $pTmp, D, zr, rscratch1\n\t"
> 3088:             "sve_lastb $dst, D, $pTmp, $src\n\t" %}

Thanks for the implementation! It mostly looks good to me. Just a trivial comment: add a comment at the end like "extract from vector(D)" like what you have done for` extractB/S` ?

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PR: https://git.openjdk.java.net/panama-vector/pull/51