Two-level semantics and code generation

AbstractWe present a two-level denotational metalanguage that is suitable for defining the semantic of PASCAL-like languages. The two levels allow for an explicit distinction between computations taking place at compile-time and computations taking place at run-time. While this distinction is perhaps not absolutely necessary for describing the input-output semantics of programming languages, it is necessary when issues like data flow analysis and code generation are considered. For an example stack-machine we show how to generate code for the run-time computations and still perform the compile-time computations. Based on an example it is argued that compiler-tricks like the use of activation records suggest how to cope with certain syntactic restrictions in the metalanguage. The correctness of the code generation is proved using Kripke-like relations and using a modified machine that can be made to loop when a certain level of recursion is encountered