There is still some work to do before we can enable GVN.

Shader-db results (SKL):

total instructions in shared programs: 15431672 -> 15431244 (<.01%)
instructions in affected programs: 102448 -> 102020 (-0.42%)
helped: 84
HURT: 0

total cycles in shared programs: 358608349 -> 358465942 (-0.04%)
cycles in affected programs: 1411090 -> 1268683 (-10.09%)
helped: 89
HURT: 2