RFR: 8315716: RISC-V: implement ChaCha20 intrinsic

[Hamlin Li]

On Mon, 25 Sep 2023 18:42:15 GMT, Antonios Printezis <tonyp 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 4326:
> 
>> 4324:     const Register tmp_addr = t1;
>> 4325:     const Register length = t2;
>> 4326:     const Register avl = x28;
> 
> Can you add the rest of the tmp registers to:
> 
> 
> // temporary register(caller-save registers)
> constexpr Register t0 = x5;
> constexpr Register t1 = x6;
> constexpr Register t2 = x7;
> 
> 
> so you can use `t3` / `t4` here instead of `x28` / `x29`?

sure

> src/hotspot/cpu/riscv/stubGenerator_riscv.cpp line 4342:
> 
>> 4340:     // Put 16 here, as com.sun.crypto.providerChaCha20Cipher.KS_MAX_LEN is 1024
>> 4341:     // in java level.
>> 4342:     __ li(avl, 16);
> 
> It's recommended to use `__ mv(avl, 16);` to copy a constant to a register.

Is there a difference between mv and li? Seems that mv(...) is calling li(...)?

  template<typename T, ENABLE_IF(std::is_integral<T>::value)>
  inline void mv(Register Rd, T o)                    { li(Rd, (int64_t)o); }

Or the recommendation is a code convention?

> src/hotspot/cpu/riscv/vm_version_riscv.cpp line 251:
> 
>> 249:     FLAG_SET_DEFAULT(UseBlockZeroing, false);
>> 250:   }
>> 251:   if (UseRVV) {
> 
> What happens if someone enables `+UseChaCha20Intrinsics` without `+UseRVV`? Maybe check if `-UseRVV` and `+UseChaCha20Intrinsics` and disable it?

Nice catch! Thanks Tony!

-------------

PR Review Comment: https://git.openjdk.org/jdk/pull/15899#discussion_r1337584807
PR Review Comment: https://git.openjdk.org/jdk/pull/15899#discussion_r1337578231
PR Review Comment: https://git.openjdk.org/jdk/pull/15899#discussion_r1337573555