[llvm] [VPlan] Introduces explicit broadcast for live-in constants. (PR #133213)

[Florian Hahn via llvm-commits]

https://github.com/fhahn commented:

Could you share a bit more on the follow-up motivation?

I'm slightly worried that this pessimizes results in some cases, as some constants can be freely broadcasted/materialized.

https://github.com/llvm/llvm-project/pull/133213