fastint2.patch adds small regression for string multiplication:
$ ./python -m timeit -s "x = 'x'" -- "x*2; x*2; x*2; x*2; x*2; x*2; x*2; x*2; x*2; x*2; "
Unpatched: 1.46 usec per loop
Patched: 1.54 usec per loop
Here is an alternative patch. It just uses existing specialized functions for integers: long_add, long_sub and long_mul. It doesn't add regression for above example with string multiplication, and it looks faster than fastint2.patch for integer multiplication.
$ ./python -m timeit -s "x = 12345" -- "x*2; x*2; x*2; x*2; x*2; x*2; x*2; x*2; x*2; x*2; "
Unpatched: 0.887 usec per loop
fastint2.patch: 0.841 usec per loop
fastint_alt.patch: 0.804 usec per loop