Concurrent skew and control step assignments in RT-level datapath synthesis

As well as the schedule affects system performance, the control skew, i.e., the arrival time difference of control signals between registers, can be utilized for improving the system performance, enhancing robustness against delay variations, etc. The simultaneous optimization of the control step assignment and the control skew assignment is more powerful technique in improving performance. By our preliminary study, we have proven that, even if the execution sequence of operations assigned to the same resource is fixed, the simultaneous optimization problem under a fixed clock period is NP-hard. In this paper, we propose a heuristic algorithm for the simultaneous control step and skew optimization under given clock period, and we show how much the simultaneous optimization improves system performance. This paper is the first one that uses the intentional skew to shorten control steps (and hence a real application time) under a specified clock period. The proposed algorithm has the potential to play a central role in various scenarios of skew-aware high level synthesis.