diff: shrink code (-85 bytes):

diff: shrink code (-85 bytes):
function                                             old     new   delta
fiddle_sum                                             8       -      -8
diffreg                                             2717    2690     -27
prepare                                              334     284     -50
------------------------------------------------------------------------------
(add/remove: 0/1 grow/shrink: 0/2 up/down: 0/-85)             Total: -85 bytes

s/ATTRIBUTE_ALWAYS_INLINE/ALWAYS_INLINE/g