Silence sign-compare warning and reduce nesting.

No functionality change.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@195932 91177308-0d34-0410-b5e6-96231b3b80d8
Refactor to remove a bit of duplication. No functionality change.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@195933 91177308-0d34-0410-b5e6-96231b3b80d8