RFR: 8334554: RISC-V: verify & fix perf of string comparison

[Hamlin Li]

On Mon, 24 Jun 2024 14:43:11 GMT, Hamlin Li <mli at openjdk.org> wrote:

>> Seems the `Error` column is huge for tests `compareToLL`.
>
> This is not a good news us (riscv), as we need to adjust the lmul for specific intrinsic, I'm not sure if different boards with same vector length  will have different preferences on the selection of lmul value.

Seem it gains benefit on compareToUU, but introduces regression on compareToLL.

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PR Review Comment: https://git.openjdk.org/jdk/pull/19825#discussion_r1651170600