Fuzion is a new language targeting safety-critical systems by building on few but powerful concepts and enabling static analysis of applications to verify their correctness. The Fuzion Intermediate Representation (FUIR) plays a key role in providing a basis for static analysis tools as well as interpreters and code generators that produce runnable programs.

FUIR has a number of aspects that are different from most other intermediate representations: Code is grouped into Fuzion features that are a common abstraction for functions, classes, types, etc. There are only 10 commands used in FUIR, calls to intrinsic features are used for operations not present as explicit commands. There is no support for loop or conditional jumps, recursion is used instead. The usual distinction between stack frames and heap instances does not exist in the FUIR.

This work-in-progress paper will give a quick overview of the Fuzion language and explain the aspects of the FUIR in more detail before presenting the impact it has on the tools processing the FUIR code.