Abstract: Methods and apparatuses are described for reducing or eliminating X-pessimism in gate-level simulation and/or formal verification. A system can identify a set of reconvergent inputs of a combinational block in a gate-level design. Next, the system can determine whether or not the combinational block is expected to exhibit X-pessimism during gate-level simulation. If the combinational block is expected to exhibit X-pessimism during gate-level simulation, the system can modify the gate-level design to reduce X-pessimism during gate-level simulation. In some embodiments, the system can build a model for the gate-level design by using unique free input variables to represent sources of indeterminate values. The system can then use the model to perform formal verification.