f8c2c4f161
A hardware loop instruction combines a subtract, compare with zero, and branch. We currently account for the compare and branch being combined into one in Cost::RateFormula, as part of more general handling for compare-branch-zero, but don't account for the subtract, leading to suboptimal decisions in some cases. Fix this in Cost::RateRegister by noticing when we have such a subtract and discounting the AddRecCost in such a case.