RFR: 8259948: Aarch64: Add cast nodes for Aarch64 Neon backend

[Ningsheng Jian]

On Tue, 20 Jul 2021 14:55:42 GMT, Wang Huang <whuang at openjdk.org> wrote:

> * In this issue, we plan to complete all missing implementation for aarch64 neon backend. For example, cast from Byte to Long, cast from Long to Byte, and so on.
> * It may be a solver of JDK-8269866, or part of it.

Thanks for the work! Some general comments:

> It may be a solver of JDK-8269866, or part of it.

I would suggest not to have a partial fix of JDK-8269866. I think you can still keep 8259948 as duplicate while targeting this to JDK-8269866 and have a fully proper fix. @theRealELiu may have some thoughts on how to have a clean fix: e.g. there may be some dependency on mid-end part, like JDK-8265244?

@theRealELiu has marked those missing rules opcode (with specific types/sizes) as unsupported in JDK-8268966, but I don't see you have unmarked them in your patch. So your newly added rules are not able to be tested. And there are some test cases included in JDK-8268966, could you please merge your test case into existing tests, if existing tests cannot cover some cases.

P.S. could you please fix the jcheck error?

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