[Attributor][NFC] Outline common pattern into helper method
[Attributor][NFC] Outline common pattern into helper method

This helper will also allow to also place logic to determine if an
abstract attribute is necessary in the first place.

git-svn-id: 0ff597fd157e6f4fc38580e8d64ab130330d2411@367966 91177308-0d34-0410-b5e6-96231b3b80d8

GPUOpen-Drivers/llvm,GPUOpen-Drivers/llvm,llvm-mirror/llvm,llvm-mirror/llvm,llvm-mirror/llvm,llvm-mirror/llvm,llvm-mirror/llvm,GPUOpen-Drivers/llvm,GPUOpen-Drivers/llvm,llvm-mirror/llvm,GPUOpen-Drivers/llvm,GPUOpen-Drivers/llvm,llvm-mirror/llvm,llvm-mirror/llvm,llvm-mirror/llvm,GPUOpen-Drivers/llvm,GPUOpen-Drivers/llvm