The longest path search problem is important in low-level worst-case execution time analysis and implies that all program executions are exhibited and inspected, via convenient abstractions, for their timing behavior. In this paper we present a definitional program unfolded that is based on the formal executable semantics of a target language. We work with K, a rewrite-based framework for the design and analysis of programming languages. Our methodology has two phases. First, it extracts directly from the executable semantics of the language, via reach ability analysis, a safe control-flow graph (CFG) approximation. Second, it unfolds the control-flow graph, using loop bounds annotations and outputs the set of all possible program executions. The two-phased definitional program un folder is implemented using the K-Maude tool, a prototype implementation of the K framework.
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