LLVM's Fortran Compiler "Flang" Makes Significant Progress But Not Yet Production Ready

Being worked on actively by a number of stakeholders in recent years has been Flang as a Fortran language front-end to the LLVM compiler stack. While not yet ready for general use, Flang has been making strides as well as showing some promising performance results.

Arm has been among the leading vendors investing engineering resources on Flang. At last weekend's FOSDEM conference in Brussels, Arm engineer Kiran Chandramohan presented on recent progress around this LLVM Fortran compiler option.

Flang can produce working executables but isn't yet deemed ready for production-use, Fortran 95 support is mostly in place, Fortran 2003 and newer features are a work-in-progress, and testing of the Flang support continues to take place across a variety of Fortran software.

Going off SPEC 2017 numbers, the Flang performance is looking quite good compared to the prior Flang implementation and compared to what GCC offers with its GFortran front-end.

The video recording of Kiran's presentation isn't yet uploaded but for those interested there is this PDF slide deck from the FOSDEM 2023 presentation with the current state of Flang.