This document contains the release notes for the Flang Fortran frontend, part of the LLVM Compiler Infrastructure, release 11.0.0. Here we describe the status of Flang in some detail, including major improvements from the previous release and new feature work. For the general LLVM release notes, see the LLVM documentation. All LLVM releases may be downloaded from the LLVM releases web site.
Flang is LLVM's Fortran front end and is new for the LLVM 11 release.
Flang is still a work in progress for this release and is included for experimentation and feedback.
Flang is able to parse a comprehensive subset of the Fortran language and check it for correctness. Flang is not yet able to generate LLVM IR for the source code and thus is unable to compile a running binary.
Flang is able to unparse the input source code into a canonical form and emit it to allow testing. Flang can also invoke an external Fortran compiler on this canonical input.
Flang's parser has comprehensive support for:
Interested users are invited to try to compile their Fortran codes with flang in and report any issues in parsing or semantic checking in bugzilla.
flang hello.f90 -o hello.bin
By default, Flang will parse the Fortran file
hello.f90 then unparse it to a canonical Fortran source file. Flang will then invoke an external Fortran compiler to compile this source file and link it, placing the resulting executable in
To specify the external Fortran compiler, set the
F18_FC environment variable to the name of the compiler binary and ensure that it is on your
PATH. The default value for
When invoked with no source input, Flang will wait for input on stdin. When invoked in this way, Flang performs the same actions as if called with
-fdebug-measure-parse-tree -funparse and does not invoke
For a full list of options that Flang supports, run
Flang's documentation is located in the
flang/docs/ directory in the LLVM monorepo.
If you have any questions or comments about Flang, please feel free to contact us via the mailing list.