Improved Coverage Driven Verification and Corner Case Analysis using Decision Diagrams

An ever-increasing portion of design effort is spent on functional verification. The verification space as the set of possible combinations of a design´s attributes is likely to be very large making it infeasible to verify each point in this space. State-of-the-art verification tools tackle this problem by using directed random generation of combinations in order to get satisfactory coverage with the desired distribution. The main drawback of using random generators is that increasing coverage grade demands lead to an exponential growth in runtime. As remedy to this deficiency coverage driven verification strategies were proposed generating only combinations not covered so far. Unfortunately, this cannot completely solve the problem since usually an arbitrary combination is generated which is then checked for previous coverage. In this work, decision diagrams are used to represent the set of valid combinations inside the complete verification space. Based on this analytical model, any number of combinations can be generated in linear time. Applied to coverage driven verification, this methodology leads to random generation orders of magnitudes faster than conventional approaches