Using the proper helper function instead of manually doing this work. No functional changes intended.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@198421 91177308-0d34-0410-b5e6-96231b3b80d8
[OpenCL] Add test case for previous commit.


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@198422 91177308-0d34-0410-b5e6-96231b3b80d8