Dependent latch identification in the reachable state space

The large number of latches in current designs increase the complexity of formal verification and logic synthesis, since the growth of latch number leads the state space to explode exponentially. One solution to this problem is to find the functional dependencies among these latches. Then, these latches can be identified as dependent latches or essential latches, where the state space can be constructed using only the essential latches. This paper proposes an approach to find the functional dependencies among latches in a sequential circuit by using SAT solvers with the Craig interpolation theorem. In addition, the proposed approach detects sequential functional dependencies existing in the reachable state space only. Experimental results show that our approach could deal with large sequential circuits with up to 1.5 K latches in a reasonable time and simultaneously identify the combinational and sequential dependent latches.