RFR: 8286301: Port JEP 425 to RISC-V [v3]

[Feilong Jiang]

On Thu, 3 Nov 2022 02:09:14 GMT, Fei Yang <fyang at openjdk.org> wrote:

>> Looks reasonable. As you mentioned that it‘s an RVC-related change, do we need this alignment when `UseRVC` is disabled?
>
> This is necessary to support for RISC-V RVC extension whether it is turned on or off. And I think we are ready to enable use of RVC by default when this hardware extension is available.

I see. If `UseRVC` is disabled, it will always be `NativeInstruction::instruction_size` aligned, and `align` will do nothing.

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PR: https://git.openjdk.org/jdk/pull/10917