Assertion quality is critical to the confidence and claims in a design's verification. In current practice, there is no metric to evaluate assertions. We introduce a methodology to rank register transfer level (RTL) assertions. We define assertion importance and assertion complexity and present efficient algorithms to compute them. Our method ranks each assertion according to its importance and complexity. We demonstrate the effectiveness of our ranking for pre-silicon verification on a detailed case study. For completeness, we study the relevance of our highly ranked assertions in a post-silicon validation context, using traced and restored signal values from the design's netlist.

Assertions are gaining importance in pre-silicon hardware verification to ensure expected design behavior. Coverage of an assertion in terms of statements of a Register Transfer Level (RTL) source code is a very accessible metric for understanding the scope of assertions and for debug. However, few methods to report it currently exist. We present a methodology to define and compute code coverage of an assertion. Our method is based on static and dynamic analysis of the RTL source code. We demonstrate the scalability and effectiveness of our approach with experimental results on real designs for both manual and automatically generated assertions.

We present GoldMine, a methodology for generating assertions automatically in hardware. Our method involves a combination of data mining and static analysis of the register transfer level (RTL) design. The RTL design is first simulated to generate data about the design's dynamic behavior. The generated data is then mined for “candidate assertions” that are likely to be invariants. The data mining algorithm is a decision-tree-based supervised learning algorithm. These candidate assertions are then passed through a formal verification engine to filter out the spurious candidates. The assertions that are attested as true by the formal engine are system invariants. These are then evaluated by a process of designer ranking that is provided as feedback to the data mining engine. We demonstrate the scalability of GoldMine by showing assertion generation of the RTL of Sun's OpenSparc T2 many-threaded processor. Our results show that GoldMine can generate complex, high coverage assertions for sequential as well as combinational designs in RTL, thereby minimizing human effort in this process. GoldMine assertions distill the random input stimulus space and can be used for calibrating directed tests. They can be used in a regression test suite of an evolving RTL. They are also useful in providing differing perspectives from the designer, as well as hints to designers for manually writing assertions.