James K. Lowden presented MESA — the Middle-End Semantic Assembler at GNU Tools Cauldron 2026. Developed through work on GCC COBOL, MESA provides a new way to inspect and work with GCC’s internal GENERIC representation.
MESA can produce a complete, concrete representation of the GENERIC tree and then reassemble that representation directly into GCC’s middle end, just as if it had been generated by a traditional language front end.
The presentation was very well received. Discussion focused not on whether MESA was useful, but on how it could be extended and applied elsewhere. Developers discussed potential uses with other GCC languages, including Fortran, as well as possible extensions involving GIMPLE and GDB.
Because MESA exposes GCC’s internal representation in a form developers can inspect and compare, it may make it easier to study how different languages express similar constructs once they reach GCC’s middle end. For example, COBOL loop definitions could potentially be compared directly with those generated by Fortran.
Parallel processing was another major theme at this year’s Cauldron, and that discussion has some interesting implications for GCC COBOL. GCC already includes OpenMP support, which Fortran uses for parallel processing. That raises the possibility of eventually applying similar techniques to COBOL operations such as INSPECT and UNSTRING, particularly when processing very large inputs.
For workloads involving gigabytes of data, parallel execution could offer substantial performance improvements. The work is still exploratory, but it highlights one of the key advantages of GCC COBOL: the ability to build on the mature optimization and parallel-processing infrastructure already available within GCC.
For readers interested in the technical details, the full MESA presentation summary from GNU Tools Cauldron 2026 is available here: