RFR: 8331577: RISC-V: C2 CountLeadingZerosV [v2]

[Fei Yang]

On Thu, 9 May 2024 10:26:16 GMT, Hamlin Li <mli at openjdk.org> wrote:

> NOTE: the reason why let dst and src share one register (i.e. `(vReg dst_src, vRegMask_V0 v0)`) in masked version is that for inactive elements, we should keep the origin value, neither `mu` or `ma` will do it.

Interesting. Is it specified anywhere? 

> BTW, I will also re-visit all existing masked version instructions to make sure it works as expected. tracked by https://bugs.openjdk.org/browse/JDK-8331992

I think this issue was considered before when we were adding support for vector api. What about the recently added ones like ReverseBytesV, PopCountVI/L?

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PR Comment: https://git.openjdk.org/jdk/pull/19153#issuecomment-2102480131