Optimizing modulo scheduling to achieve reuse and concurrency for stream processors

Abstract

Both reuse and concurrency are performance-critical for stream processors. When applying loop unrolling and software pipelining separately to streamlevel loops, either reuse or concurrency or both may be inadequately exploited. In this paper, we optimize modulo scheduling to maximize stream reuse and improve concurrency for stream-level loops. The key insight is that an unrolled and softwarepipelined stream-level loop could be described by a set of reuse equations. Guided by reuse equations, a reuse-aware modulo scheduling algorithm is developed to simultaneously optimize the two performance objectives, reuse, and concurrency, for a loop in a unified framework. Moreover, we describe a code generation algorithm to automatically produce the optimized loop from a given loop. The experimental results obtained on FT64 and by simulation demonstrate the effectiveness of the proposed approach.