[llvm] [LV] Add vector library call legalization via VPlan transform (PR #197661)

[Simon Pilgrim via llvm-commits]

https://github.com/RKSimon commented:

Shouldn't the backend be handling this? We REALLY need to stop trying to do all this veclib call matching in the vectorizers, keep to regular llvm math vector intrinsics at the full width and then split/legalise this properly in the backend. I realise that represents a lot more yak shaving, but you're just digging yourself a hole here :(

https://github.com/llvm/llvm-project/pull/197661