An experiment in mixed compilation/interpretation

One of the classic forms of intermediate represen-tation used for communication between compiler front-ends and back-ends are those based on ab-stract stack machines. It is possible to compile the stack machine instructions into machine code by means of an interpretive code generator, or to simulate the stack machine at runtime using an in-terpreter. This paper describes an approach inter-mediate between these two extremes. The front-end for a commercial Modula 2 com-piler was ported to the \industry standard PC", and a partially compiling back-end written. The object code runs with the assistance of an interpreter, but may be linked with libraries which are fully com-piled. The intent was to provide a programming environment on the PC which is identical to that of the same compilers on 32-bit UNIX machines. This objective has been met, and the compiler is available to educational institutions as free-ware. The design basis of the new compiler is described, and the performance critically evaluated. [Key words and phrases: compilers, interpretive code generation, abstract stack machines.]