Safe and efficient elimination of infeasible execution paths in WCET estimation

Reasoning about the timing properties of a program is indispensable in the development of time critical systems where failure to meet deadlines can result in loss of life or material. To this end having tools to calculate safe and tight Worst Case Execution Time (WCET) bounds can be very valuable. In most of the approaches to date a lot of pessimism is attributed to the fact that many paths that are infeasible are not excluded from the WCET computations. To remedy this, user annotations to the source code were proposed and used. Unfortunately, there is no guarantee that these annotations are always correct. This fact renders such a manual approach unacceptable in the case of R/T systems where safety is an absolute priority. In this paper another approach for the safe elimination of infeasible execution paths is presented. This method is based on the R/T programming language SIGNAL and its internal Dynamic Graph representation.