Abstract
Timing-driven placement is a well-known technique that relocates cells along critical paths to improve timing. Traditional approaches fix timing violation while treating clock skew as given. We propose a flip-flop swapping algorithm for adding useful skew. We derive a gain function reflecting timing slack variation from flip-flop swapping. By employing a hybrid of net-based and path-based structure, it facilitates trade off between timing accuracy and time complexity. We test our approach with the benchmark contents of top three winners of ICCAD 2014 contest. Experiment results show our placer achieves better timing improvement than their solutions.