Use dyn_cast instead of isa && cast.
No functionality change.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@177836 91177308-0d34-0410-b5e6-96231b3b80d8
Minor cleanups. No functionality change.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@177837 91177308-0d34-0410-b5e6-96231b3b80d8