Assign the ordering of SDNodes in a much less intrusive fashion. After the

Assign the ordering of SDNodes in a much less intrusive fashion. After the
"visit*" method is called, take the newly created nodes, walk them in a DFS
fashion, and if they don't have an ordering set, then give it one.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@94757 91177308-0d34-0410-b5e6-96231b3b80d8