  This paper presents the context-updates synthesis component of Chisel--a tool
that synthesizes a program slicer directly from a given algebraic specification
of a programming language operational semantics. (By context-updates we
understand programming language constructs such as goto instructions or
function calls.) The context-updates synthesis follows two directions: an
overapproximating phase that extracts a set of potential context-update
constructs and an underapproximating phase that refines the results of the
first step by testing the behaviour of the context-updates constructs produced
at the previous phase. We use two experimental semantics that cover two types
of language paradigms: high-level imperative and low-level assembly languages
and we conduct the tests on standard benchmarks used in avionics.
