[llvm] [RISCV] Optimize divide by constant for VP intrinsics (PR #125991)

[Luke Lau via llvm-commits]

lukel97 wrote:

> RISC-V seems to be the only active development of VP intrinsics in tree. We the RISC-V community, should agree on what's important to us and prioritize where we spend effort.

Agreed. If the only use case for non-trapping VP intrinsics was EVL tail folding in the loop vectorizer then adding optimisations for them is less of a priority. We should probably talk about this in the RISC-V LLVM sync up on Thursday. 

It's worth noting though that the loop vectorizer still emits load/store VP intrinsics, and they might be missing combines. Is this something you've looked at already in your downstream?

> Is this question about the max case or the entire patch?

The entire patch, I just chose a random case to check if instcombine did any strength reduction

https://github.com/llvm/llvm-project/pull/125991