[llvm] [LV] Compute register usage for interleaving on VPlan. (PR #126437)

[Luke Lau via llvm-commits]

lukel97 wrote:

> > In VPlan the loads are all now in the one place, and there's now 10 loads alive at the same time:
> 
> Can't we instruct VPlan to spread out loads near their uses like the legacy model?

I think that would be quite difficult because an interleave group is a single recipe with multiple values if I understand correctly. 

I think that the VPlan model is actually being more accurate in regards to the IR that the loop vectorizer emits, i.e. with the loads bundled together. It’s more of a coincidence that the legacy version happened to match it closer to what it looked like after scheduling/once the shuffles were sunk?

https://github.com/llvm/llvm-project/pull/126437