[llvm] [LoopVectorizer] Prune VFs based on plan register pressure (PR #132190)

[Sam Tebbs via llvm-commits]

SamTebbs33 wrote:

> > Thank you for the approvals. I'll rebase and merge once Elvis's PR is in.
> 
> Could you link the depenency in the description? My understanding was that all dependencies already landed for the PR

Sure it's [this](https://github.com/llvm/llvm-project/pull/113903) one. This PR introduces a regression in mve-reduction-types.ll ([context](https://github.com/llvm/llvm-project/pull/132190#discussion_r2013585095)) and 113903 eliminates that regression.

https://github.com/llvm/llvm-project/pull/132190