[llvm] [VPlan] Don't convert widen recipes to VP intrinsics in EVL transform (PR #126177)

[Mel Chen via llvm-commits]

Mel-Chen wrote:

> I had the same question too, I checked beforehand and it looks like LoopVectorizationLegality is used when the VPlan is constructed to mask off any lanes that would trap e.g.:

What a surprise! I didn't realize that converting select to vp.merge had this use case. 
Could you add this test case to prevent others from having similar confusion? :)



https://github.com/llvm/llvm-project/pull/126177