I took another look at this, and tried applying it to 3.6 and running the latest benchmarks. It applied cleanly, and the benchmark results were similar, this time unpack_sequence and spectral_norm were slower. Spectral norm makes sense, it's doing lots of FP addition. The unpack_sequence instruction looks like it already has optimizations for unpacking lists and tuples onto the stack, and running dis on the test showed that it's completely dominated calls to unpack_sequence, load_fast, and store_fast so I still don't know what's going on there.