Expression Coverability Analysis: Improving code coverage with model checking

Code coverage analysis provides metrics to quantify the degree of verification completeness. It also allows the designer to identify possible bugs or redundant code thus speeding verification. Many verification engineers report that the most time consuming area of code coverage analysis is the identification and documentation of intrinsically uncoverable expression cases. With manual inspection of the code being especially time consuming and error prone, automatic methods of identifying uncoverable expression cases are highly desirable. Our work extends the model-checking-based coverability analysis work at IBM [5] to support analysing the coverability of expression cases. We present results of applying our implementation on industrial scale designs provided by Motorola. We also analyse how coding style can impact the coverability of expressions and suggest how expression coverability analysis can be applied within the verification flow.