Latency-tolerant software pipelining in a production compiler

Abstract

In this paper we investigate the benefit of scheduling non-critical loads for a higher latency during software pipelining. "Non-critical" denotes those loads that have sufficient slack in the cyclic data dependence graph so that increasing the scheduling distance to their first use can only increase the number of stages of the software pipeline, but should not increase the lengths of the individual stages, the initiation interval (II). The associated cost is in many cases negligible, but the memory stall reduction due to improved latency coverage and load clustering in the schedule can be considerable.