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Speculative execution can enhance the average execution time by executing parts of the code which may or may not be needed. In some cases, rollback is necessary if the computation turns out to be invalid. However, speculative execution should be applied carefully to real-time systems so that the worst-case execution path will not be extended. We have developed a set of compiler transformations to detect safe opportunities for speculative execution in real-time programs and transform the code without jeopardizing the timeliness of the system. To capture various properties of real-time programs that affect applicability and profitability of speculative execution, we have conducted an experiment using randomly generated real-time programs. In this paper, we present simulation results indicating effects of speculative execution on average execution time and program timeliness. In addition, we examine impacts of various program properties, such as locality of variable references, and frequency of conditionals and while loops. |
