The following tests regressed on SNB, IVB, and HSW:
This has been bisected to this commit:
Author: Timothy Arceri <firstname.lastname@example.org>
Date: Fri Nov 23 11:49:19 2018 +1100
nir: propagate known constant values into the if-then branch
I've reverted this for now. The fix is going to be more complex than I first thought.