Constraint generation for software-based post-silicon bug masking with scalable resynthesis technique for constraint optimization

Due to the dramatic increase in design complexity, verifying the functional correctness of a circuit is becoming more difficult. Therefore, bugs may escape all verification efforts and be detected after tape-out. While most existing solutions focus on fixing the problem on the hardware, in this work we propose a different methodology that tries to generate constraints which can be used to mask the bugs using software. This is achieved by utilizing formal reachability analysis to extract the conditions that can trigger the bugs. By synthesizing the bug conditions, we can derive input constraints for the software so that the hardware bugs will never be exposed. In addition, we observe that such constraints have special characteristics: they have small onset terms and flexible minterms. To facilitate the use of our methodology, we also propose a novel resynthesis technique to reduce the complexity of the constraints. In this way, software can be modified to run correctly on the buggy hardware, which can improve system quality without the high cost of respin.