Software pipelining: a comparison and improvement

Software pipelining can significantly increase the execution rate of loops. Each of the four major software pipelining algorithms takes a different approach to software pipelining. This paper discusses each method and explores some of the similarities and differences among the methods. On loops consisting of a single basic block, the perfect pipelining algorithm is the only software pipelining algorithm that currently achieves time optimality, in the absence of resource constraints. A technique for unrolling the loop before pipelining is presented as an improvement to software pipelining, as it can allow Lam´s algorithm to achieve time optimality for these restricted loops. Unrolling has an advantage over perfect pipelining because it can reduce the code space required for the software pipeline