Guiding RTL Test Generation Using Relevant Potential Invariants

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Virginia Tech

In this thesis, we propose to use relevant potential invariants in a simulation-based swarmintelligence-based test generation technique to generate relevant test vectors for design validation at the Register Transfer Level (RTL). Providing useful guidance to the test generator for such techniques is critical. In our approach, we provide guidance by exploiting potential invariants in the design. These potential invariants are obtained using random stimuli such that they are true under these stimuli. Since these potential invariants are only likely to be true, we try to generate stimuli that can falsify them. Any such vectors would help reach some corners of the design. However, the space of potential invariants can be extremely large. To reduce execution time, we also implement a two-layer filter to remove the irrelevant potential invariants that may not contribute in reaching difficult states. With the filter, the vectors generated thus help to reduce the overall test length while still reach the same coverage as considering all unfiltered potential invariants. Experimental results show that with only the filtered potential invariants, we were able to reach equal or better branch coverage than that reported by BEACON in the ITC99 benchmarks, with considerable reduction in vector lengths, at reduced execution time.

Ant Colony Optimization, Potential Invariants, Branch Coverage, Verilator