Simple analysis of partial worst-case execution paths on general control flow graphs

Abstract

One of the most important computations in static worst-case execution time analyses is the path analysis which computes the potentially most time-consuming execution path in a program. This is typically done either with an implicit path computation based on solving an integer linear program, or with explicit path computations directly on the program's control flow graph. The former approach is powerful and comparably simple to use but hard to extend and to combine with other program analyses due to its restriction to the linear equation model. The latter approaches are often restricted to well-structured graphs, suffer from inaccuracy or require nontrivial structural analyses or graph transformations upfront or during their computations. In this paper, we propose a generalized computational model and a comprehensive explicit path analysis that operates on arbitrary directed control flow graphs. We propose simple and yet effective techniques to deal with unstructured control flows and complex flow fact models. The analysis does not require a control flow graph to be mutable, is non-recursive, fast, and provides the means to compute all worst-case paths from arbitrary source nodes. It is well suited for solving local problems and the computation of partial solutions, which is highly relevant for problems related to scheduling and execution modes alike.