RFR: 8366333: AArch64: Enhance SVE subword type implementation of vector compress [v3]

[erifan]

On Mon, 29 Sep 2025 18:54:35 GMT, Vladimir Ivanov <vlivanov at openjdk.org> wrote:

>> Done, thanks!
>
> The following reads slightly better, but it's up to you how to shape it.
> 
> FloatRegister vzr = vtmp3;
> sve_dup(vzr, B, 0);

Done, thanks!

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PR Review Comment: https://git.openjdk.org/jdk/pull/27188#discussion_r2409551881