RFR: 8259948: Aarch64: Add cast nodes for Aarch64 Neon backend [v2]

[Wu Yan]

On Fri, 13 Aug 2021 00:58:14 GMT, Eric Liu <eliu at openjdk.org> wrote:

>> This rule has fixed the problem you mentioned. As for other problems, I'm not sure whether they still exist.
>
> Currently, we are *not* going to support small vector lane count which less than 64 bits[1][2]. I prefer to fix the mid-end problem first and remove this kind of rules in this patch.
>  
> [1] https://github.com/openjdk/jdk/blob/master/src/hotspot/share/opto/matcher.hpp#L341
> [2] https://github.com/openjdk/jdk/blob/master/src/hotspot/cpu/aarch64/aarch64.ad#L2491

Hi, The vector cast rule below 64bit has been deleted, and the patch to fix the mid-end problem has been submitted in https://github.com/openjdk/jdk/pull/5160. Thanks for your suggestion.

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PR: https://git.openjdk.java.net/jdk/pull/4839