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.

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.

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