d3d96e2057
Both clang and gfortran support the -fopenmp-simd flag, which enables OpenMP support only for simd constructs, while disabling the rest of OpenMP. Implement the appropriate parse tree rewriting to remove non-SIMD OpenMP constructs at the parsing stage. Add a new SimdOnly flang OpenMP IR pass which rewrites generated OpenMP FIR to handle untangling composite simd constructs, and clean up OpenMP operations leftover after the parse tree rewriting stage. With this approach, the two parts of the logic required to make the flag work can be self-contained within the parse tree rewriter and the MLIR pass, respectively. It does not need to be implemented within the core lowering logic itself. The flag is expected to have no effect if -fopenmp is passed explicitly, and is only expected to remove OpenMP constructs, not things like OpenMP library functions calls. This matches the behaviour of other compilers. --------- Signed-off-by: Kajetan Puchalski <kajetan.puchalski@arm.com>
Flang
Flang is a ground-up implementation of a Fortran front end written in modern C++. It started off as the f18 project (https://github.com/flang-compiler/f18) with an aim to replace the previous flang project (https://github.com/flang-compiler/flang) and address its various deficiencies. F18 was subsequently accepted into the LLVM project and rechristened as Flang.
Please note that flang is not ready yet for production usage.
Getting Started
Read more about flang in the docs directory. Start with the compiler overview.
To better understand Fortran as a language and the specific grammar accepted by flang, read Fortran For C Programmers and flang's specifications of the Fortran grammar and the OpenMP grammar.
Treatment of language extensions is covered in this document.
To understand the compilers handling of intrinsics, see the discussion of intrinsics.
To understand how a flang program communicates with libraries at runtime, see the discussion of runtime descriptors.
If you're interested in contributing to the compiler, read the style guide and also review how flang uses modern C++ features.
If you are interested in writing new documentation, follow LLVM's Markdown style guide.
Consult the Getting Started with Flang for information on building and running flang.