[llvm] [VPlan] Introduce multi-branch recipe, use for multi-exit loops (WIP). (PR #109193)

[Florian Hahn via llvm-commits]

fhahn wrote:

Circling back after the discussion at the vectorizer sync on Tuesday: selecting the exit blocks outside the vector region should be sufficient as a starting point. I will update https://github.com/llvm/llvm-project/pull/112138 in the next few days (currently traveling to the US) and move it out of draft status.

https://github.com/llvm/llvm-project/pull/109193