RFR: 8319184: RISC-V: improve MD5 intrinsic

[Hamlin Li]

On Wed, 1 Nov 2023 15:05:09 GMT, Antonios Printezis <tonyp at openjdk.org> wrote:

> Tweaks to the RISC-V MD5 intrinsic.
> 
> * do the loads from the buffer more incrementally instead of all in one go
> * don't mask off the top 32 bits of a register before an addw instruction, as addw will ignore them anyway
> * remove the rmask32 register, as the mask is not needed any more (only at the start / end and it's 
> * cleanup some of the register usage

src/hotspot/cpu/riscv/stubGenerator_riscv.cpp line 3967:

> 3965:     // a += ac
> 3966:     __ mv(rtmp3, t);
> 3967:     __ addw(a, a, rtmp3);

Could these 2 lines could be replaced with addiw? although no performance gain, but could be simpler.

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PR Review Comment: https://git.openjdk.org/jdk/pull/16453#discussion_r1379086324