Abstract. The full call strings method is the most general, simplest, and most precise method of performing context sensitive interprocedural data flow analysis. It remembers contexts using call strings. For full precision, all call strings up to a prescribed length must be constructed. Two limitations of this method are (a) it cannot be used for frameworks with infinite lattices, and (b) the prescribed length is quadratic in the size of the lattice resulting in an impractically large number of call strings. These limitations have resulted in a proliferation of ad hoc methods which compromise on generality, precision, or simplicity.We propose a variant of the classical full call strings method which reduces the number of call strings, and hence the analysis time, by orders of magnitude as corroborated by our empirical measurements. It reduces the worst case call string length from quadratic in the size of the lattice to linear. Further, unlike the classical method, this worst case length need not be reached. Our approach retains the precision, generality, and simplicity of call strings method without imposing any additional constraints. It can accommodate demand-driven approximations and hence can be used for frameworks with infinite lattices.

SystemC is a widely used tool for prototyping Systems-on-a-Chip. Being implemented as a C++ library, a plain C++ compiler is sufficient to compile and simulate a SystemC program. However, a SystemC program needs to be processed by a dedicated tool in order to visualize, formally verify, debug and/or optimize the architecture. In this paper we focus on the tools (called front-ends) used in the initial stages of processing SystemC programs. We describe the challenges in developing SystemC front-ends and present a survey of existing solutions. The limitations and capabilities of these tools are compared for various features of SystemC and intended back-end applications. We present typical examples that front-ends should ideally be able to process, and give theoretical limitations as well as experimental results of existing tools.

Interprocedural data flow analysis extends the scope of analysis across procedure boundaries in search of increased optimization opportunities. Call strings based approach is a general approach for performing flow and context sensitive interprocedural analysis. It maintains a history of calls along with the data flow information in the form of call strings, which are sequences of unfinished calls. Recursive programs may need infinite call strings for interprocedural data flow analysis. For bit vector frameworks this method is believed to require all call strings of lengths up to 3K , where K is the maximum number of distinct call sites in any call chain.We combine the nature of information flows in bit-vector data flow analysis with the structure of interprocedurally valid paths to bound the call strings. Instead of bounding the length of call strings, we bound the number of occurrences of any call site in a call string. We show that the call strings in which a call site appears at most three times, are sufficient for convergence on interprocedural maximum fixed point solution. Though this results in the same worst case length of call strings, it does not require constructing all call strings up to length 3K . Our empirical measurements on recursive programs show that our bound reduces the lengths and the number of call strings, and hence the analysis time, significantly.

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