[llvm] [LV][NFC] Add cost model tests for VPInstructionWithType (PR #200135)

[Florian Hahn via llvm-commits]

fhahn wrote:

> As far as I can tell the code in both implementations for the scalar cast case are the same, with the only difference being that in https://github.com/llvm/llvm-project/pull/140623 the code bails out if there isn't an underlying value.

Yep exactly, all VPInstructionWithType created currently (and checked in the new tests) do not have underlying instructions.  With https://github.com/llvm/llvm-project/pull/140623, those single-scalar replicate recipes will instead be VPInstructionWIthType with underlying value

https://github.com/llvm/llvm-project/pull/200135