Blocks that contain only a single branch instruction to the next block can be skipped in analyzing the loop-nest structure.
This is currently done by getSingleSuccessor().
However, the branch instruction might have multiple targets which happen to all be the same.
In this case, the block should still be considered as empty and skipped.
An example is test/Transforms/LoopInterchange/update-condbranch-duplicate-successors.ll (the LIT test for this patch is modified from it as well).