Comparing Tail Duplication with CompensationCode in Single Path Global

Global instruction scheduling allows operations to move across basic block boundaries to create tighter schedules. When operations move above control ow joins, some code duplication is generally necessary to preserve semantics. Tail duplication and compensation code are approaches to duplicating the necessary code, used by Superblock Scheduling and Trace Scheduling respectively. Compensation code needs much more engineering eeort, but ooers the possibility of less code growth. We implemented both algorithms to evaluate whether the extra eeort is worthwhile. Experimental results show that trace scheduling does not always create less code growth and often creates more.