This new patch also updates the code generation for list comprehensions.
Here are some micro-benchmarks:

./python -m timeit -s "l = range(100)" "[x for x in l]"
Before: 100000 loops, best of 3: 14.9 usec per loop
After: 100000 loops, best of 3: 12.5 usec per loop

./python -m timeit -s "l = range(100)" "[x for x in l if x]"
Before: 10000 loops, best of 3: 24.1 usec per loop
After: 100000 loops, best of 3: 18.8 usec per loop

./python -m timeit -s "l = range(100)" "[x for x in l if not x]"
Before: 100000 loops, best of 3: 15.5 usec per loop
After: 100000 loops, best of 3: 11.9 usec per loop

Please note that this patch is orthogonal with Neal's patch in #2183, so
the two combined should be quite interesting for the list comprehensions
bytecode.