[llvm] [RISCV] Prune dead LI in vsetvli coalescing with trivially dead vsetvli (PR #98647)

[Luke Lau via llvm-commits]

https://github.com/lukel97 approved this pull request.

LGTM. I'll note that this is similar to #90629, but the latter is generalized to all dead instructions not just LIs. Do you think it's still worth picking up after this lands?

https://github.com/llvm/llvm-project/pull/98647