Fast Postplacement Optimization Using Functional Symmetries

The timing-convergence problem arises because estimations made during logic synthesis may not be met during physical design. In this paper, an efficient rewiring engine is proposed to explore maximal freedom after placement. The most important feature of this approach is that the existing placement solution is left intact throughout the optimization. A linear-time algorithm is proposed to detect functional symmetries in the Boolean network which are then used as the basis for rewiring. Integration with an existing gate-sizing algorithm further proves the effectiveness of our technique. Three applications are demonstrated: delay, power, and reliability optimization.