Otherwise we will end up with an extra instruction to compare the
result of the inot.

On BDW:

total instructions in shared programs: 13060620 -> 13060481 (-0.00%)
instructions in affected programs: 103379 -> 103240 (-0.13%)
helped: 127
HURT: 0

total cycles in shared programs: 256590950 -> 256587408 (-0.00%)
cycles in affected programs: 11324730 -> 11321188 (-0.03%)
helped: 114
HURT: 21

Reviewed-by: Jason Ekstrand <jason@jlekstrand.net>