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

[Andrew Haley]

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.

The big question for all of this is: what is the test coverage?

src/hotspot/cpu/aarch64/assembler_aarch64.hpp line 2831:

> 2829:     f(0b000001, 15, 10), rf(Vn, 5), rf(Vd, 0);
> 2830:   }
> 2831: 

Please add the comment

// Advanced SIMD scalar copy
``` 
here

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