Cluster: Compilers and Timing Analysis

Run-time guarantees play an important role in the area of embedded systems and especially hard real-time systems. These systems are typically subject to stringent timing constraints which often result from the interaction with the surrounding physical environment. It is essential that the computations are completed within their associated time bounds; otherwise severe damages may result. Therefore, a schedulability analysis has to be performed which guarantees that all timing constraints will be met (also called timing validation). All existing techniques for schedulability analysis require the worst case execution time (WCET) of each task in the system to be known before the task is executed. Since in general, the problem of computing WCETs is not decidable, estimations of the WCET have to be calculated. These estimations have to be safe, i.e., they may never underestimate the real execution time. Furthermore, they should be tight, i.e., the overestimation should be as small as possible.

In modern microprocessor architectures caches and pipelines are key features for improving performance. Unfortunately, they make the analysis of the execution behaviour of instructions very difficult since this behaviour now depends on the execution history. Therefore, the classical approaches to worst case execution time prediction are not directly applicable or lead to results exceeding the real execution time by orders of magnitude. This may influence the degree of success of timing validations or may lead to a waste of hardware resources and more expensive hardware. For products which are manufactured in high quantity, e.g., in the automobile or telecommunications markets this possibly results in high expenses.

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