The LLVM Compiler Infrastructure

This directory and its sub-directories contain source code for LLVM,a toolkit for the construction of highly optimized compilers,optimizers, and run-time environments.

The README briefly describes how to get started with building LLVM.For more information on how to contribute to the LLVM project, pleasetake a look at theContributing to LLVM guide.

Getting Started with the LLVM System

Taken from https://llvm.org/docs/GettingStarted.html.

Overview

Welcome to the LLVM project!

The LLVM project has multiple components. The core of the project isitself called "LLVM". This contains all of the tools, libraries, and headerfiles needed to process intermediate representations and convert them intoobject files. Tools include an assembler, disassembler, bitcode analyzer, andbitcode optimizer. It also contains basic regression tests.

C-like languages use the Clang front end. Thiscomponent compiles C, C++, Objective-C, and Objective-C++ code into LLVM bitcode-- and from there into object files, using LLVM.

Other components include:the libc++ C++ standard library,the LLD linker, and more.

Getting the Source Code and Building LLVM

The LLVM Getting Started documentation may be out of date. The ClangGetting Started page might have moreaccurate information.

This is an example work-flow and configuration to get and build the LLVM source:

1. Checkout LLVM (including related sub-projects like Clang):

   • git clone https://github.com/llvm/llvm-project.git

   • Or, on windows, git clone --config core.autocrlf=false https://github.com/llvm/llvm-project.git

2. Configure and build LLVM and Clang:

   • cd llvm-project

   • cmake -S llvm -B build -G <generator> [options]

     Some common build system generators are:

     • Ninja --- for generating Ninjabuild files. Most llvm developers use Ninja.
     • Unix Makefiles --- for generating make-compatible parallel makefiles.
     • Visual Studio --- for generating Visual Studio projects andsolutions.
     • Xcode --- for generating Xcode projects.

     Some common options:

     • -DLLVM_ENABLE_PROJECTS='...' and -DLLVM_ENABLE_RUNTIMES='...' ---semicolon-separated list of the LLVM sub-projects and runtimes you'd like toadditionally build. LLVM_ENABLE_PROJECTS can include any of: clang,clang-tools-extra, cross-project-tests, flang, libc, libclc, lld, lldb,mlir, openmp, polly, or pstl. LLVM_ENABLE_RUNTIMES can include any oflibcxx, libcxxabi, libunwind, compiler-rt, libc or openmp. Some runtimeprojects can be specified either in LLVM_ENABLE_PROJECTS or inLLVM_ENABLE_RUNTIMES.

       For example, to build LLVM, Clang, libcxx, and libcxxabi, use-DLLVM_ENABLE_PROJECTS="clang" -DLLVM_ENABLE_RUNTIMES="libcxx;libcxxabi".

     • -DCMAKE_INSTALL_PREFIX=directory --- Specify for directory the fullpath name of where you want the LLVM tools and libraries to be installed(default /usr/local). Be careful if you install runtime libraries: ifyour system uses those provided by LLVM (like libc++ or libc++abi), youmust not overwrite your system's copy of those libraries, since thatcould render your system unusable. In general, using something like/usr is not advised, but /usr/local is fine.

     • -DCMAKE_BUILD_TYPE=type --- Valid options for type are Debug,Release, RelWithDebInfo, and MinSizeRel. Default is Debug.

     • -DLLVM_ENABLE_ASSERTIONS=On --- Compile with assertion checks enabled(default is Yes for Debug builds, No for all other build types).

   • cmake --build build [-- [options] <target>] or your build system specified abovedirectly.

     • The default target (i.e. ninja or make) will build all of LLVM.

     • The check-all target (i.e. ninja check-all) will run theregression tests to ensure everything is in working order.

     • CMake will generate targets for each tool and library, and mostLLVM sub-projects generate their own check-<project> target.

     • Running a serial build will be slow. To improve speed, try running aparallel build. That's done by default in Ninja; for make, use the option-j NNN, where NNN is the number of parallel jobs, e.g. the number ofCPUs you have.

   • For more information see CMake

Consult theGetting Started with LLVMpage for detailed information on configuring and compiling LLVM. You can visitDirectory Layoutto learn about the layout of the source code tree.

Getting in touch

Join LLVM Discourse forums, discord chat or #llvm IRC channel on OFTC.

The LLVM project has adopted a code of conduct forparticipants to all modes of communication within the project.