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

[Andrew Haley]

On Wed, 4 Aug 2021 09:57:45 GMT, Andrew Haley <aph 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.
>
> src/hotspot/cpu/aarch64/assembler_aarch64.hpp line 2047:
> 
>> 2045:     rf(Rn, 5), rf(Rd, 0);
>> 2046:   }
>> 2047: 
> 
> This instruction is part of "AdvSIMD two-reg misc" along with things like fsqrt. Please put it there with the other instructions using the same encoding, and please using the existing logic.

And given that it has a different name from Arm's name, please add a comment for the reader.

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