StmtTree: An Easy-to-Use yet Versatile Fortran Transformation Toolkit

TL;DR

StmtTree is a versatile Fortran transformation toolkit that simplifies processing legacy Fortran-77 codes by providing an abstracted statement tree representation and user-friendly APIs, enabling efficient customization and modernization efforts.

Contribution

The paper introduces StmtTree, a novel toolkit that abstracts Fortran grammar into a statement tree, facilitating easier code transformation and modernization of legacy Fortran codes.

Findings

Effective adaptation to legacy Fortran-77 codes

Complex transformations achievable with fewer than 100 lines of Python

Simplifies creation of customized Fortran transformation tools

Abstract

The Fortran programming language continues to dominate the scientific computing community, with many production codes written in the outdated Fortran-77 dialect, yet with many non-standard extensions such as Cray poiters. This creates significant maintenance burden within the community, with tremendous efforts devoted to modernization. However, despite the modern age of advanced compiler frameworks, processing and transforming old Fortran codes remains challenging. In this paper, we present StmtTree, a new Fortran code transformation toolkit to address this issue. StmtTree abstracts the Fortran grammar into statement tree, offering both a low-level representation manipulation API and a high-level, easy-to-use query and manipulation mini-language. StmtTree simplifies the creation of customized Fortran transformation tools. Experiments show that StmtTree adapts well to legacy Fortran-77 codes, and complex tools such as removing unused statements can be developed with fewer than 100 lines of python code.