[llvm] [AMDGPU][AMDGPULateCodeGenPrepare] Combine scalarized selects back into vector selects (PR #173990)

[Matt Arsenault via llvm-commits]

https://github.com/arsenm commented:

This seems more like a job for SLPVectorizer 

https://github.com/llvm/llvm-project/pull/173990