RFR: 8319716: RISC-V: Add SHA-2

[Robbin Ehn]

On Mon, 13 Nov 2023 09:06:34 GMT, Fei Yang <fyang at openjdk.org> wrote:

>> Yes, this is a total mess.
>> For bystanders this is a 'simple' march to clang:
>> `rv64im0_a2p1_f2p2_d2p2_c2p0_v1p0_zicsr2p0_zifencei2p0_zmmul1p0_zacas1p0_zve32f1p0_zve32x1p0_zve64d1p0_zve64f1p0_zve64x1p0_zvl128b1p0_zvl32b1p0_zvl64b1p0`
>> A simple RVA23U64 CPU may have like 40 extensions, a high performance server class CPU may have well over a hundred.
>> 
>> Just the scalar crypto ones:
>> `Zbkb, Zbkc, Zbkx, Zknd, Zkne, Zknh, Zksed, Zksh, Zkr, Zkt, Zkn, Zks, Zk`
>> 
>> It is no reasonable to add all these as flags.
>> So flags for the collections seems like much better idea.
>> But we probably need to be able to turn off a sub-extension such UseZvknhb.
>> "-XX:+UseVectorCryptoExt:zvknhb=false"
>> Suggestions welcome.
>> 
>> Just top of my head, at the moment I need to supply this crazy arch string to compiler, obj dump, qemu(bit different but still crazy :) ) and there doesn't seem to be a solution near, so maybe we should be able to supply that arch string to the VM also.
>> `-XX:UseArch=rv64im0_a2p1_f2p2_d2p2_c2p0_v1p0_zicsr2p0_zifencei2p0_zmmul1p0_zacas1p0_zve32f1p0_zve32x1p0_zve64d1p0_zve64f1p0_zve64x1p0_zvl128b1p0_zvl32b1p0_zvl64b1p0`
>
> I think that's what RISC-V profiles are for [1] which make some basic extensions mandatory for each profile. And we already have JVM options like `UseRVA20U64` and `UseRVA22U64` for riscv. But there are still some optional extensions for each profile, say RVV for RVA22U64. So instead of feeding a rather long march to the JVM, I feel it's more reasonable to have some JVM options at the extension level (instead of sub-extension level) as suggested by @robehn.
> 
> Personally, I would suggest something slightly different. Say:
>  "-XX:VectorCryptoExt=zvknhb", "-XX:VectorCryptoExt=zvknhb_zvkb", or "-XX:VectorCryptoExt=all"
> 
> This way we will still be able to distinguish specific sub-extensions while keeping one JVM option for each extension/collection.
> 
> [1] https://github.com/riscv/riscv-profiles/blob/main/profiles.adoc

Let's take it on the list:
https://mail.openjdk.org/pipermail/riscv-port-dev/2023-November/001211.html

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PR Review Comment: https://git.openjdk.org/jdk/pull/16562#discussion_r1391138003