UNRET: A Transformation-based technique for software pipelining with resource constraints

This paper presents UNRET (unrolling and retiming), a new approach for resourceconstrained software pipelining. UNRET aims at finding a loop schedule with maximum resource usage. UNRET explores schedules in decreasing order of resource usage. For each theoretical resource usage, both the unrolling degree of the loop (K) and the initiation interval of the schedule (II) are analitically computed by using new and effective methods. Next, the loop is unrolled K times and data dependences are successively retimed in order to find a valid schedule with II cycles. The effectiveness of UNRET has been proven by presenting results on different benchmarks. A comparison with modulo scheduling is also provided, showing that UNRET can improve results obtained by modulo scheduling. Keywords: Software Pipelining, Instruction-level parallelism, Loop unrolling, Retiming, Resource Utilization 1 Introduction Software pipelining comprises a family of techniques aimed at the overlaped execution of severa..