Tuning the WCET of embedded applications

Abstract

It is advantageous to not only calculate the WCET of an application, but to also perform transformations to reduce the WCET since an application with a lower WCET is less likely to violate its timing constraints. In this paper we describe an environment consisting of an interactive compilation system and a timing analyzer, where a user can interactively tune the WCET of an application. After each optimization phase is applied, the timing analyzer is automatically invoked to calculate the WCET of the function being tuned. Thus, a user can easily gauge the progress of reducing the WCET. In addition, the user can apply a genetic algorithm to search for an effective optimization sequence that best reduces the WCET. Using the genetic algorithm, we show that the WCET for a number of applications can be reduced by 7% on average as compared to the default batch optimization sequence.