This refactor base on the patch https://reviews.llvm.org/D61248. Update the scheduler strategy for system Z to adapt with the schedule state forward infrastructure.
nit: so that, its... -> so its scheduled state...
I find this explanation some what confusing and it's also different from the function definition below.
Should it be something similar to what was doc below originally on line 37?
when enter the MBB -> when entering the MBB
Should the dbgs() be on a new line?
stragegy -> strategy