Check register classes also when changing them.

We have the same assertion in createVirtualRegister.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@176959 91177308-0d34-0410-b5e6-96231b3b80d8
No functionality change. Use unreachable in getCompileUnit.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@176962 91177308-0d34-0410-b5e6-96231b3b80d8
No functionality change. Use unreachable in getCUOffset.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@176963 91177308-0d34-0410-b5e6-96231b3b80d8