How do I iterate over nested SCCs in an LLVM FunctionPass?

As part of the FunctionPass that I'm writing in LLVM, I need to iterate over the strongly-connected components of each Function's DAG. As per Eli Bendersky's article, I'm using the scc_iterator to do so.

However, I've noticed that nested SCCs appear to be treated as a single large SCC. This seems to correspond to a nested for loop in my test program. I've also tried using the LoopInfo to access the nested loop, but for one reason or another the internal loop isn't showing up.

Does LLVM provide a way of iterating over SCCs within an SCC (as provided by the scc_iterator, or any other method)?