Previous work on formally modelling and analysing program compilation has shown the need for a simple and expressive semantics for assembler level programs.

Assembler programs contain unstructured jumps and previous formalisms have modelled these by using continuations, or by embedding the program in an explicit emulator. We propose a simpler approach, which uses techniques from compiler theory in a formal setting. This approach is based on an interpretation of programs as collections of program paths, each of which has a weakest liberal precondition semantics.

We then demonstrate, by example, how we can use this formalism to justify the compilation of block-structured high-level language programs into assembler.