[llvm] [VPlan] Introduce scalar loop header in plan, remove VPLiveOut. (PR #109975)

[David Sherwood via llvm-commits]

david-arm wrote:

I just noticed this patch today. I have a patch to enable vectorisation of more early exit loops that require adding live outs from the early exiting block - https://github.com/llvm/llvm-project/pull/88385. I hadn't realised that VPLiveOuts were going to be removed from the vplan.

@fhahn If possible, can you point me at the patch or code that shows how we model outside uses of loop values in the exit block? I will need to update PR #88385 to ensure we generate the correct final value in the early exit block.

https://github.com/llvm/llvm-project/pull/109975