The Beneet of Predicated Execution for Software Pipelining

Software pipelining is a compile-time scheduling technique that overlaps successive loop iterations to expose operation-level parallelism. An important problem with the development of eeective software pipelin-ing algorithms is how to handle loops with conditional branches. Conditional branches increase the complexity and decrease the eeectiveness of software pipelin-ing algorithms by introducing many possible execution paths into the scheduling scope. This paper presents an empirical study of the importance of an architectural support, referred to as predicated execution, on the eeectiveness of software pipelining. In order to perform an in-depth analysis, we 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, are implemented in a prototype compiler. Experiments based on important loops from numeric applications show that predicated execution support substantially improves the eeectiveness of the modulo scheduling algorithm .