RFR: 8315716: RISC-V: implement ChaCha20 intrinsic [v2]

[Robbin Ehn]

On Thu, 28 Sep 2023 16:54:14 GMT, Hamlin Li <mli at openjdk.org> wrote:

>> Only vector version is included in this patch.
>> 
>> ### Test
>> The patch passed the jdk tests found via `find test/jdk/ -iname *ChaCha*`
>
> Hamlin Li has updated the pull request incrementally with one additional commit since the last revision:
> 
>   revert adding t3-t6

@gctony hopefully we can agree on the register :)
As I said adding new temps in assembler_riscv.hpp will make these register very hard to 'reclaim' in a few years.
So I think we should try to keep some available for future features and such.

Can you look and see if @Hamlin-Li latest changes are okay?

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PR Comment: https://git.openjdk.org/jdk/pull/15899#issuecomment-1740374812