RFR: 8345110: RISC-V: Optimize and and clean up byte reverse assembler routines

[Fei Yang]

On Thu, 28 Nov 2024 11:58:30 GMT, Robbin Ehn <rehn at openjdk.org> wrote:

> I liked that you used rev8 directly in AD because it makes it very clear that we do not clobber t1. (as it otherwise it is one of the default registers)

Yeah. Great!

> As all uses of revb_w use dst == src, please consider a helper version which only needs one registers passed. I.e. "__ revb_w(temp);"

Thanks for the suggestion! Personally, I prefer to follow the mnemonics as specified by the riscv spec (like `rev8 rd, rs`) for all places to be consistent in style.

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PR Comment: https://git.openjdk.org/jdk/pull/22410#issuecomment-2506169653