A method for debugging of pipelined processors in formal verification by Correspondence Checking

Abstract

Presented is a method for debugging of pipelined processors in their formal verification with the highly automatic and scalable approach of Correspondence Checking, where a pipelined/superscalar/VLIW implementation is compared against a non-pipelined specification via an inductive correctness criterion based on symbolic simulation in a way that guarantees the correctness of the implementation for all possible execution scenarios. The benefit from the proposed method increases with the complexity of the processor under formal verification. For a 12-stage VLIW processor that imitates the Intel Itanium in many features, the method reduced the size of the EUFM correctness formulas from buggy processors by up to an order of magnitude, the number of Boolean variables in the equivalent propositional correctness formulas and the number of 1s in the counterexample traces by up to 2 orders of magnitude, and resulted in an average speedup in detecting the bugs of 2 orders of magnitude, thus increasing the productivity of the processor designers.