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This is the first part of the effort to make parsing of clause modifiers more uniform and robust. Currently, when multiple modifiers are allowed, the parser will expect them to appear in a hard-coded order. Additionally, modifier properties (such as "ultimate") are checked separately for each case. The overall plan is 1. Extract all modifiers into their own top-level classes, and then equip them with sets of common properties that will allow performing the property checks generically, without refering to the specific kind of the modifier. 2. Define a parser (as a separate class) for each modifier. 3. For each clause define a union (std::variant) of all allowable modifiers, and parse the modifiers as a list of these unions. The intent is also to isolate parts of the code that could eventually be auto-generated. OpenMP modifier overhaul: #1/3
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.