Displaying dependence graphs: a hierarchical approach

We present a method to handle data- and control-flow information, represented as simplified system dependence graphs. As soon as a program is bigger than a few dozens of lines of code, its dependence graph becomes unreadable with standard drawing tools, since it contains far too many nodes and edges. In our approach, we propose to decompose the program into a hierarchy of groups that are likely to be of manageable size. We implemented a tool that first builds this hierarchy and stores it in a data base. A graphical interface allows then to browse this hierarchy to visualize the dependences of each group, to annote the nodes or groups and possibly to refine the proposed hierarchy. This paper introduces our approach for program decomposition, it describes our tool for dependence exploration and discusses the preliminary results we obtained with a few sample programs.