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Welcome to Flang’s documentation — The Flang Compiler
The Flang Compiler
Welcome to Flang’s documentation
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 Getting Involved for tips on how to get in touch with us and to learn more about the current status.
Using Flang¶
- Getting Started
- Flang command line argument reference
- Flang Fortran Standards Support
- Fortran Extensions supported by Flang
- Compiler directives supported by Flang
- Directive Details
- Flang OpenMP Support
- Flang support for REAL(16) math intrinsics
- Flang support for UNSIGNED type
- Frequently Asked Questions (FAQ)
Contributing to Flang¶
Design Documents¶
- Aliasing in Fortran
- Aliasing analysis in FIR
- Array Composition
- Assumed-shape arrays repacking
- Assumed-Rank Objects
- Bijective Internal Name Uniquing
- Representation of Fortran function calls
- Implementation of
CHARACTERtypes in Flang - Complex Operations
- Control Flow Graph
- Debug Generation
DO CONCURRENTisn’t necessarily concurrentDO CONCURRENTmapping to OpenMP- A first take on Fortran 202X features for LLVM Flang
- Design: FIR Array operations
- FIR Language Reference
- Flang drivers
- A Fortran feature history cheat sheet
- Design: Fortran IR
- Fortran Tests in the LLVM Test Suite
- High-Level Fortran IR (HLFIR)
- 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
Intrinsictypes in f18 - Semantics: Resolving Labels and Construct Names
- Module Files
- OpenACC in Flang
- OpenACC dialect: Fortran descriptor management in the offload data environment
- OpenMP 4.5 Grammar
- OpenMP Declare Target
- Fortran descriptor type mapping for OpenMP offload
- OpenMP Semantic Analysis
- Compiler options comparison
- Overview of Compiler Phases
- Multi-Image Parallel Fortran Runtime
- Parameterized Derived Types (PDTs)
- Parser Combinators
- The Flang Parser
- Polymorphic Entities
- Fortran Preprocessing
- Procedure Pointer
- Runtime Descriptors
- Environment variables of significance to Fortran execution
- The derived type runtime information table
- Semantic Analysis
- Fortran 2018 Grammar
- Stack arrays pass
Indices and tables¶
© Copyright 2017-2025, The Flang Team.
Last updated on Dec 26, 2025.
Created using Sphinx 7.2.6.