[llvm] [VPlan] Move auxiliary declarations out of VPlan.h (NFC). (PR #124104)

[Florian Hahn via llvm-commits]

fhahn wrote:

> Given the size of the changes in this patch I wonder if it's worth considering breaking down into a fewer smaller patches, if possible? I'm just thinking potential disruption to other developers. If all the changes in this patch depend upon each other that's fine though.

I originally thought it might be less disruptive to move things together to their new locations, instead of moving them piece by piece, potentially causing conflicts on each commit. There are some bits that could be moved independently (e.g. VPInterleavedAccessInfo/VPlanSLP), if that would be preferred.

I think the definitions moved in this patch hopefully shouldn't cause too much pain.

There are other moves that might be more painful, like moving most recipe definitions, which I plan to propose separately, to further reduce the main header size and allow for better further recipe additions.

https://github.com/llvm/llvm-project/pull/124104