Instruction Scheduling in the Presence of Structural Hazards: An Integer Programming Approach to Software Pipelining

Software pipelining is an eecient instruction scheduling method to exploit the multiple instructions issue capability of modern VLIW architectures. In this paper we develop a precise mathematical formulation based on ILP (Integer Linear Programming) for the software pipelining problem for architectures involving structural hazards. Compared to other heuris-tic methods as well as an ILP-based method 1], a distinct feature of the proposed formulation is that it uses classical pipeline theory, in particular those relating to the forbidden latency set. The proposed software pipelining technique has been successfully applied to derive rate-optimal schedules under resource constraints. The method was used in experiments on 1008 loop kernels taken from various scientiic benchmark programs. Performance results of our experiments and comparison with a leading heuristic method reveal that the ILP based exact solution does have a signiicant performance advantage over the heuristic methods, though at the expense of a larger computation time.