Finding and Finessing Static Islands in Dynamically Scheduled Circuits

In high-level synthesis, scheduling is the process that determines the start time of each operation in hardware. A hardware design can be scheduled either at compile time (static), run time (dynamic), or both. Recent research has shown that combining dynamic and static scheduling can achieve high performance and small area. However, there is still a challenge to determine which part to schedule statically and which part dynamically. An inappropriate choice can lead to suboptimal design quality. This paper proposes a heuristic-driven approach to automatically determine 'static islands' - i.e., code regions that are amenable for static scheduling. Over a set of benchmarks where our approach is applicable, we show that our tool can achieve on average a 3.8-fold reduction in area combined with a 13% performance boost through automatic identification and synthesis of static islands from fully dynamically scheduled circuits. The performance of the resulting hardware is close to optimum (as determined by an exhaustive enumeration of all possible static islands).