[llvm] [RISCV] Clear vill for whole vector register moves in vsetvli insertion (PR #118283)

[Luke Lau via llvm-commits]

lukel97 wrote:

> Do we need to add `Uses = [VTYPE]` to the whole register move instructions in RISCVInstrInfoV.td?

The whole register move instructions use `RVInstV` which already has `Uses = [VL, VTYPE]`, so I think they're safe.

https://github.com/llvm/llvm-project/pull/118283