[llvm] [LV][VPlan] Add initial support for CSA vectorization (PR #106560)

[Michael Maitland via llvm-commits]

michaelmaitland wrote:

>  is it possible to not nest the test under RISCV? I realized that you've said it's disabled in BasicTTIImpl, but having a separate cas.ll under each target wouldn't be ideal, no?

I can do this. It's a good idea.

https://github.com/llvm/llvm-project/pull/106560