A novel framework of register allocation for software pipelining

Abstract

Although software pipelining has been proposed as one of the most important loop scheduling methods, simultaneous scheduling and register allocation is less understood and remains an open problem [28]. The objective of this paper is to develop a unified algorithmic framework for concurrent scheduling and register allocation to support time-optimal software pipelining. A key intuition leading to this surprisingly simple formulation and its efficient solution is the association of maximum computation rate of a program graph with its critical cycles due to Reiter's pioneering work on Karp-Miller computation graphs [29]. In particular, our method generalizes the work by Callahan, Carr and Kennedy on scalar expansion[6], the work by Lam on modular variable expansion for software pipelined loops [20], and the work by Rau et al. on register allocation for modulo scheduled loops[28].