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Currently, we indicate to the runtime that implicit scalar captures are firstprivate (via map and capture types), enough for the runtime trace to treat it as such, but we do not CodeGen the IR in such a way that we can take full advantage of this aspect of the OpenMP specification. This patch seeks to change that by applying the correct symbol flags (firstprivate/implicit) to the implicitly captured scalars within target regions, which then triggers the delayed privitization code generation for these symbols, bringing the code generation in-line with the explicit firstpriviate clause. Currently, similarly to the delayed privitization I have sheltered this segment of code behind the EnabledDelayedPrivitization flag, as without it, we'll trigger an compiler error for firstprivate not being supported any time we implicitly capture a scalar and try to firstprivitize it, in future when this flag is removed it can also be removed here. So, for now, you need to enable this via providing the compiler the flag on compilation of any programs.
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.