Exploiting Positive Equality in a Logic of Equality with Uninterpreted Functions

  • Randal E. Bryant
  • Steven German
  • Miroslav N. Velev
Conference paper
Part of the Lecture Notes in Computer Science book series (LNCS, volume 1633)


In using the logic of equality with unininterpreted functions to verify hardware systems, specific characteristics of the formula describing the correctness condition can be exploited when deciding its validity.We distinguish a class of terms we call “p-terms” for which equality comparisons can appear only in monotonically positive formulas. By applying suitable abstractions to the hardware model, we can express the functionality of data values and instruction addresses flowing through an instruction pipeline with p-terms. Adecision procedure can exploit the restricted uses of p-terms by considering only “maximally diverse” interpretations of the associated function symbols, where every function application yields a different value except when constrained by functional consistency.We present a procedure that translates the original formula into one in propositional logic by interpreting the formula over a domain of fixedlength bit vectors and using vectors of propositional variables to encode domain variables. By exploiting maximal diversity, this procedure can greatly reduce the number of propositional variables that must be introduced.

We present experimental results demonstrating the efficiency of this approach when verifying pipelined processors using the method proposed by Burch and Dill. Exploiting positive equality allows us to overcome the exponential blow-up experienced previously [VB98] when verifying microprocessors with load, store, and branch instructions.


Decision Procedure Propositional Logic Positive Equality Function Symbol Domain Variable 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.


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Copyright information

© Springer-Verlag Berlin Heidelberg 1999

Authors and Affiliations

  • Randal E. Bryant
    • 1
  • Steven German
    • 2
  • Miroslav N. Velev
    • 3
  1. 1.Computer ScienceCarnegie Mellon UniversityPittsburgh
  2. 2.IBMWatson Research CenterYorktown Hts.
  3. 3.Electrical and Computer EngineeringCarnegie Mellon UniversityPittsburgh

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