Automatic Derivation of Loop Bounds and Infeasible Paths for WCET Analysis Using Abstract Execution

  • Authors:

  • Jan Gustafsson;Andreas Ermedahl;Christer Sandberg;Bjorn Lisper

  • Affiliations:

  • Malardalen University, Sweden;Malardalen University, Sweden;Malardalen University, Sweden;Malardalen University, Sweden

  • Venue:
  • RTSS '06 Proceedings of the 27th IEEE International Real-Time Systems Symposium
  • Year:
  • 2006

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Abstract

Static Worst-Case Execution Time (WCET) analysis is a technique to derive upper bounds for the execution times of programs. Such bounds are crucial when designing and verifying real-time systems. A key component for statically deriving safe and tight WCET bounds is information on the possible program flow through the program. Such flow information can be provided manually by user annotations, or automatically by a flow analysis. To make WCET analysis as simple and safe as possible, it should preferably be automatically derived, with no or very limited user interaction. In this paper we present a method for deriving such flow information called abstract execution. This method can automatically calculate loop bounds, bounds for including nested loops, as well as many types of infeasible paths. Our evaluations show that it can calculate WCET estimates automatically, without any user annotations, for a range of benchmark programs, and that our techniques for nested loops and infeasible paths sometimes can give substantially better WCET estimates than using loop bounds analysis only.