Register Optimization for Maximum Throughput Loop Pipelining Register Optimization for Maximum Throughput Loop Pipelining

UNRET (unrolling and retiming) is an approach for resource-constrained loop pipelining that aims at nding a loop schedule with maximum throughput and minimum register pressure. This paper proposes an algorithm in two phases. In the rst phase, a schedule with maximum throughput is found for a given set of resource constraints. To do this, diierent unrolling degrees are explored in decreasing order of throughput. For each theoretical throughput, both the unrolling degree of the loop and the expected initiation interval of the schedule are analytically computed by using new and eeective methods. In the second phase, the number of registers required by the schedule is reduced while maintining the throughput. The eeectiveness of the proposed approach is shown by presenting results on well-known benchmarks. Results show that UNRET may obtain faster schedules than other approaches, also reducing the register pressure.