Efficient DAG construction and heuristic calculation for instruction scheduling

A number of heuristic algorithms for DAG-based instruction scheduling have been proposed over the past few years. In this paper, we explore the efficiency of three DAG construction algorithms and survey 26 proposed heuristics and their methods of calculation. Six scheduling algorithms are analyzed in terms of DAG construction and heuristic use. DAG suuctural statistics and scheduling times for the three construction algorithms are given for several popular benchmarks. The tablebuilding algorithms are shown to extremely efficient for programs with large basic blocks and yet appropriately handle the problem of retaining important transitive arcs. The node revisitation overhead of intermediate heuristic calculation steps is also investigated and shown to be negligible.