[llvm] [VPlan] Move widening decisions to VPlanWideningDecisions.cpp (NFC) (PR #209887)

[Florian Hahn via llvm-commits]

fhahn wrote:

> Hm, not sure about this patch, because widening decisions are all over the place really: take the simple example of how legalizeAndOptimizeInductions narrows to single scalars?

Originally I only planned to move memory widening decision logic, but I don't think there's any reason we cannot consolidate most (all?) relevant VPlan code in a single file? Moved createInterleaveGroups, legalizeAndOptimizeInductions and narrowInterleaveGroups as well.



https://github.com/llvm/llvm-project/pull/209887