Deriving annotations for tight calculation of execution time

Abstract A number of methods have been presented to calculate the worst case execution time WCET of realtime programs However to properly handle semantic dependencies which in most cases is needed to reduce overestimation all these methods require extra semantic infor mation to be given by the programmer manual annotations for paths loops and recursion depth To manually derive these annotations is of ten dicult and the process is errorprone In this paper we present a new method to automatically derive safe and tight annotations for paths and loops We illustrate our method by giving some examples and by presenting a prototype tool implementing the method for a subset of C Realtime systems are systems in which the correctness depends not only on the results of computations but also on the time at which the result is produced To be able to guarantee the deadlines of a realtime system the software execution time is needed before runtim