Syntactic Optimizations for PSL Verification Alessandro Cimatti 1 , Marco Roveri 1 , and Stefano Tonetta 2 1 ITC-irst Trento, Italy {cimatti,roveri}@itc.it 2 University of Lugano, Lugano, Switzerland tonettas@lu.unisi.ch Abstract. The IEEE standard Property Specification Language (PSL) allows to express all ω-regular properties mixing Linear Temporal Logic (LTL) with Se- quential Extended Regular Expressions (SEREs), and is increasingly used in many phases of the hardware design cycle, from specification to verification. In recent works, we propose a modular and symbolic PSL compilation that is extremely fast in conversion time and outperforms by several orders of magni- tude translators based on the explicit construction and minimization of automata. Unfortunately, our approach creates rather redundant automata, which result in a penalty in verification time. In this paper, we propose a set of syntactic simplifications that enable to signif- icantly improve the verification time without paying the price of automata sim- plifications. A thorough experimental analysis over large sets of paradigmatic properties shows that our approach drastically reduces the overall verification time. 1 Introduction The IEEE standard Property Specification Language PSL [1] is increasingly used in several phases of the design flows: it is a means to describe behavioral requirements, such as assumptions about the environment in which the design is expected to operate, internal behavioral requirements, and further constraints that arise during the design process from specification to verification. The most important fragment of PSL combines Linear Temporal Logic (LTL) [2] with Sequential Extended Regular Expressions (SERE), a variant of classical regular expressions [1]. This combination results in ω-regular expressiveness, and enables to express many properties of practical interest in a compact and readable way. The conversion from PSL to Nondeterministic B¨ uchi Automata (NBAs) is an en- abling factor for the the adaptation of standard verification tools, and has been recently investigated in several works (e.g. [3,4,5,6,7]). [3] describes a classical approach based on Alternating B¨ uchi Automata (ABA): the SEREs occurring in the PSL formula are first translated into minimum Nondeterministic Finite Automata (NFA); the NFAs are then combined bottom up and the overall PSL formula is translated into an ABA; the ABA is finally translated into an NBA by means of the Miyano-Hayashi (MH) construction [8]. [4] specializes this approach to SAT- based bounded model checking, exploiting the fact that alternating automata are weak. In [5], a symbolic encoding, based on MH, of the NBA corresponding to the ABA of O. Grumberg and M. Huth (Eds.): TACAS 2007, LNCS 4424, pp. 505–518, 2007. c  Springer-Verlag Berlin Heidelberg 2007