Hierarchical Reduction

Abstract

Hierarchical reduction is a unified approach to scheduling both within and across basic blocks. The motivation for the technique is to make software pipelining applicable to all innermost loops, including those containing conditional statements. Software pipelining has previously been defined only for loops containing straight-line code bodies. A simple conditional statement in the loop would have rendered the technique inapplicable. A loop such as the following would have been extremely inefficient on a heavily pipelined and parallel data path.