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.<>