RFR: 8315716: RISC-V: implement ChaCha20 intrinsic

[Ludovic Henry]

On Mon, 25 Sep 2023 12:15:58 GMT, Robbin Ehn <rehn 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/vm_version_riscv.cpp line 191:
> 
>> 189:   if (UseRVV && FLAG_IS_DEFAULT(UseChaCha20Intrinsics)) {
>> 190:     FLAG_SET_DEFAULT(UseChaCha20Intrinsics, true);
>> 191:   }
> 
> Just below this we may set RVV to false.
> I would put this just above "#ifdef COMPILER2" or so.

👍 https://github.com/openjdk/jdk/pull/15899/files#diff-7b173d6e5834de13749c8333192fef5a874628a67b90a5d8d06235d507542ac4R255 seems like the ideal place.

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PR Review Comment: https://git.openjdk.org/jdk/pull/15899#discussion_r1335862298