An approach to symbolic worst-case execution time analysis

Using the constant value for the worst case execution time for all calls to a subprogram is safe but pessimistic. We address the problem of tailoring the WCET of each call to a subprogram by building the WCET as an algebraic expression parameterised with some of the subprogram parameters. The WCET of each call may then be constrained to particular ranges of values that lead to tighter WCET. The technique relies on the power of computational algebra systems to perform sophisticated simplifications and evaluation of the intermediate expressions. The same approach also allows to obtain tighter estimations of nested loop iterations which may also be tailored for different execution calls. This approach requires the description of the non-functional behaviour of the code with annotations included as specially formatted comments.