Welcome to Flang’s documentation

Flang is LLVM’s Fortran frontend that can be found here. It is often referred to as “LLVM Flang” to differentiate itself from “Classic Flang” - these are two separate and independent Fortran compilers. LLVM Flang is under active development. While it is capable of generating executables for a number of examples, some functionality is still missing. See GettingInvolved for tips on how to get in touch with us and to learn more about the current status.

• Flang |version| (In-Progress) Release Notes

Contributing to Flang

• C++14/17 features used in f18
• Flang C++ Style Guide
• Design Guideline
• Fortran For C Programmers
• Getting Involved
• Getting Started
• How to implement a Sematic Check in Flang
• Pull request checklist

Design Documents

• Aliasing in Fortran
• Aliasing analysis in FIR
• Aliasing rules
• Array Composition
• Assumed-Rank Objects
• Bijective Internal Name Uniquing
• Representation of Fortran function calls
• Implementation of CHARACTER types in f18
• Complex Operations
• Control Flow Graph
• Compiler directives supported by Flang
• DO CONCURRENT isn’t necessarily concurrent
• Fortran Extensions supported by Flang
• A first take on Fortran 202X features for LLVM Flang
• Design: FIR Array operations
• array_merge_store
• FIR Language Reference
• Flang command line argument reference
• Flang drivers
• CMake Support
• Testing
• Frontend Driver Plugins
• LLVM Pass Plugins
• A Fortran feature history cheat sheet
• Design: Fortran IR
• Fortran Tests in the LLVM Test Suite
• Variable and Expression value concepts in HLFIR
• Alternatives that were not retained
• Fortran I/O Runtime Library Internal Design
• Trampolines for pointers to internal procedures.
• A categorization of standard (2018) and extended Fortran intrinsic procedures
• Implementation of Intrinsic types in f18
• Semantics: Resolving Labels and Construct Names
• Module Files
• OpenACC in Flang
• OpenMP 4.5 Grammar
• OpenMP Semantic Analysis
• Compiler options comparison
• Overview of Compiler Phases
• Analysis
• Lowering
• Object code generation and linking
• Parameterized Derived Types (PDTs)
• Fortran standard
• Testing
• Current TODOs
• Parser Combinators
• The F18 Parser
• Polymorphic Entities
• Testing
• Current TODOs
• Fortran Preprocessing
• Procedure Pointer
• Testing
• Current TODOs
• Runtime Descriptors
• The derived type runtime information table
• Semantic Analysis
• Fortran 2018 Grammar
• -fstack-arrays

Indices and tables

• Index

• Module Index

• Search Page