On BDW:

total instructions in shared programs: 13061890 -> 13061877 (-0.00%)
instructions in affected programs: 2441 -> 2428 (-0.53%)
helped: 13
HURT: 0

total cycles in shared programs: 256612254 -> 256611784 (-0.00%)
cycles in affected programs: 16418 -> 15948 (-2.86%)
helped: 10
HURT: 2

V2: don't use ffma directly

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