Function memoization and unique object representation for ACL2 functions
ACL2 '06 Proceedings of the sixth international workshop on the ACL2 theorem prover and its applications
Centaur Technology Media Unit Verification
CAV '09 Proceedings of the 21st International Conference on Computer Aided Verification
Verifying VIA Nano microprocessor components
Proceedings of the 2010 Conference on Formal Methods in Computer-Aided Design
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We have created an experimental extension to ACL2 that provides a means to symbolically evaluate ACL2 expressions. This modified implementation can be used to compute the 'general' application of an ACL2 function to generalized data. In particular, we use uBDDs to represent functions from Boolean variables to finite sets of ACL2 objects, and for guard-checked ACL2 functions we can automatically create corresponding generalized functions to operate on such generalized data. The DEFTHM hint mechanism has been extended to permit the direct application of symbolic simulation as a part of a proof attempt. This extension made it possible to directly verify the Legato Challenge using only symbolic simulation; this challenge involves proving the correctness of a 6502 assembly-language program that performs an 8-bit by 8-bit multiplication through repeated addition. We need only provide the initial symbolic data, i.e., two 8-bit, symbolic numbers, and we symbolically simulate the assemblylanguage program by symbolically simulating an ISA-level 6502-program interpreter that produces a symbolic result that we compare to its specification.