[llvm] [CodeGen] Teach ReplaceWithVeclib split vector llvm.sincos when only sin/cos veclib mappings exist (PR #194639)

[Matt Arsenault via llvm-commits]

https://github.com/arsenm commented:

ReplaceWithVecLib should be overhauled to use RuntimeLibcallsInfo instead of TargetLibraryInfo. The way the vector functions were added to TargetLibraryInfo is kind of wonky. CodeGen should be using RuntimeLibcallsInfo, and treating the vector case like any other instructions with a set of target legal types 

https://github.com/llvm/llvm-project/pull/194639