Register and Instruction Coverage Analysis for Different RISC-V ISA Modules

Fault coverage analysis and fault simulation are well-established methods for the qualification of test vectors in hardware design. However, their role in virtual prototyping and the correlation to later steps in the design process need further investigation. We introduce a metric for RISC-V instruction and register coverage for binary software. The metric measures if RISC-V instruction types are executed and if GPRs, CSRs, and FPRs are accessed. The analysis is applied by the means of a virtual prototype which is based on an abstract instruction and register model with direct correspondence to their bit level representation. In this context, we analyzed three different openly available test suites: the RISC-V architectural testing framework, the RISC-V unit tests, and programs which are automatically generated by the RISC-V Torture test generator. We discuss their tradeoffs and show that by combining them to a unified test suite we can arrive at a 100% GPR and FPR register coverage and a 98.7% instruction type coverage.