Maybe I'm just missing it, but I don't see in this description any explanation of how to handle hash collisions - ie, when two keys map to the same hash value. Do you iterate through an infinite series of secondary hash functions when you run out of distinguishing bits? Or do you bottom out at a table that you linearly scan?

Overall, it seems like the algorithm is "maintain a trie on the hash values, using an auxiliary bitmap and popcnt to determine the index within any trie node." Does that miss anything?