RFR: 8315716: RISC-V: implement ChaCha20 intrinsic

[Robbin Ehn]

On Mon, 25 Sep 2023 13:03:11 GMT, Ludovic Henry <luhenry 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*`
>
> src/hotspot/cpu/riscv/stubGenerator_riscv.cpp line 4287:
> 
>> 4285:   }
>> 4286: 
>> 4287:   void quarter_round(VectorRegister aVec, VectorRegister bVec,
> 
> Please rename that to `chacha20_quarter_round` to make it clear it belongs to the chacha20 algorithm

And should be static.
Ignore. I missed they are in scope of class StubGenerator.

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PR Review Comment: https://git.openjdk.org/jdk/pull/15899#discussion_r1335871092