The benefit of predicated execution for software pipelining

An empirical study of the importance of an architectural support, referred to as predicted execution, for the effectiveness of software pipelining is presented. In particular, the analysis is designed to help future microprocessor designers to determine whether predicated execution support is worthwhile given their own estimation of the increased hardware cost. To perform an in-depth analysis, the authors focus on Rau´s modulo scheduling algorithm for software pipelining. Three versions of the modulo scheduling algorithm, one with and two without predicated execution support, were implemented in a prototype compiler. Experiments based on important loops from numeric applications showed that predicated execution support substantially improved the effectiveness of the modulo scheduling algorithm.