RFR: 8286301: Port JEP 425 to RISC-V [v4]

[Fei Yang]

On Fri, 4 Nov 2022 08:32:40 GMT, Jie Fu <jiefu at openjdk.org> wrote:

> The shared code change looks good to me.
> 
> I'm not sure if it's possible to eliminate all the platform-dependent code. But the current version looks good enough to me. Thanks.

Thanks for looking at this. I think we have enough reviews for both the shared code and riscv-specific changes now.
Let's proceed so that this won't block reviewing of PR for the loom ppc64 port.

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