Algorithms for Infeasible Path Calculation

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 in static WCET analysis is to derive flow information, such as loop bounds and infeasible paths. Such flow information can be provided as either as annotations by the user, can be automatically calculated by a flow analysis, or by a combination of both. To make the analysis as simple, automatic and safe as possible, this flow information should be calculated automatically with no or very limited user interaction. In this paper we present three novel algorithms to calculate infeasible paths. The algorithms are all designed to be simple and efficient, both in terms of generated flow facts and in analysis running time. The algorithms have been implemented and tested for a set of WCET benchmarks programs.