[llvm] [VPlan] Support VPWidenCastRecipe in isSingleScalar. (PR #143552)

[Florian Hahn via llvm-commits]

https://github.com/fhahn commented:

Could you add a brief description of the problematic issue? IIUC the issue is that a VPWidenCastRecipe could have been narrowed/extended, and then we cannot convert it to a VPReplicateRecipe, which clones the underlying instruction.

IIRC this should be solved by using VPInstructionWithType for single-scalar casts https://github.com/llvm/llvm-project/pull/140623

https://github.com/llvm/llvm-project/pull/143552