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Atomic Control Options are used to specify architectural characteristics to help lowering of atomic operations. The options used are: `-f[no-]atomic-remote-memory`, `-f[no-]atomic-fine-grained-memory`, `-f[no-]atomic-ignore-denormal-mode`. Legacy option `-m[no-]unsafe-fp-atomics` is aliased to `-f[no-]ignore-denormal-mode`. More details can be found in https://github.com/llvm/llvm-project/pull/102569. This PR implements the frontend support for these options with OpenMP atomic in flang. Backend changes are available in the draft PR: https://github.com/llvm/llvm-project/pull/143769 which will be raised after this merged.
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.