Impact of loop transformations on software reliability

Application-level correctness is a useful and widely accepted concept for many kinds of applications in this modern world. The results of some applications, such as multimedia, may be incorrect due to transient hardware faults or soft-errors, but they are still acceptable from a user´s perspective. Thus, it is worthwhile to develop approaches to guarantee application-level correctness in software, instead of hardware, to reduce cost and save energy. Many previous research efforts presented solutions to identify parts of programs that may potentially cause unacceptable results, and placed error detectors to improve reliability. On the other hand, we observe that loop transformations have the ability to improve reliability. By applying suitable loop transformations, some critical instructions may become non-critical. In this paper we propose a metric to analyze the reliability impact of each loop transformation. Thus, we can guide a compiler to optimize programs not only for reliability improvement, but for energy saving. The experimental results show that our analysis perfectly matches the results of fault injection, and achieves a 39.72% energy saving while improving performance by 52.16% when compared with [1]. To our knowledge, this is the first work that considers a software reliability by loop transformations.