1# The LLVM Compiler Infrastructure 2 3This directory and its sub-directories contain source code for LLVM, 4a toolkit for the construction of highly optimized compilers, 5optimizers, and run-time environments. 6 7The README briefly describes how to get started with building LLVM. 8For more information on how to contribute to the LLVM project, please 9take a look at the 10[Contributing to LLVM](https://llvm.org/docs/Contributing.html) guide. 11 12## Getting Started with the LLVM System 13 14Taken from https://llvm.org/docs/GettingStarted.html. 15 16### Overview 17 18Welcome to the LLVM project! 19 20The LLVM project has multiple components. The core of the project is 21itself called "LLVM". This contains all of the tools, libraries, and header 22files needed to process intermediate representations and convert them into 23object files. Tools include an assembler, disassembler, bitcode analyzer, and 24bitcode optimizer. It also contains basic regression tests. 25 26C-like languages use the [Clang](http://clang.llvm.org/) front end. This 27component compiles C, C++, Objective-C, and Objective-C++ code into LLVM bitcode 28-- and from there into object files, using LLVM. 29 30Other components include: 31the [libc++ C++ standard library](https://libcxx.llvm.org), 32the [LLD linker](https://lld.llvm.org), and more. 33 34### Getting the Source Code and Building LLVM 35 36The LLVM Getting Started documentation may be out of date. The [Clang 37Getting Started](http://clang.llvm.org/get_started.html) page might have more 38accurate information. 39 40This is an example work-flow and configuration to get and build the LLVM source: 41 421. Checkout LLVM (including related sub-projects like Clang): 43 44 * ``git clone https://github.com/llvm/llvm-project.git`` 45 46 * Or, on windows, ``git clone --config core.autocrlf=false 47 https://github.com/llvm/llvm-project.git`` 48 492. Configure and build LLVM and Clang: 50 51 * ``cd llvm-project`` 52 53 * ``cmake -S llvm -B build -G <generator> [options]`` 54 55 Some common build system generators are: 56 57 * ``Ninja`` --- for generating [Ninja](https://ninja-build.org) 58 build files. Most llvm developers use Ninja. 59 * ``Unix Makefiles`` --- for generating make-compatible parallel makefiles. 60 * ``Visual Studio`` --- for generating Visual Studio projects and 61 solutions. 62 * ``Xcode`` --- for generating Xcode projects. 63 64 Some common options: 65 66 * ``-DLLVM_ENABLE_PROJECTS='...'`` and ``-DLLVM_ENABLE_RUNTIMES='...'`` --- 67 semicolon-separated list of the LLVM sub-projects and runtimes you'd like to 68 additionally build. ``LLVM_ENABLE_PROJECTS`` can include any of: clang, 69 clang-tools-extra, cross-project-tests, flang, libc, libclc, lld, lldb, 70 mlir, openmp, polly, or pstl. ``LLVM_ENABLE_RUNTIMES`` can include any of 71 libcxx, libcxxabi, libunwind, compiler-rt, libc or openmp. Some runtime 72 projects can be specified either in ``LLVM_ENABLE_PROJECTS`` or in 73 ``LLVM_ENABLE_RUNTIMES``. 74 75 For example, to build LLVM, Clang, libcxx, and libcxxabi, use 76 ``-DLLVM_ENABLE_PROJECTS="clang" -DLLVM_ENABLE_RUNTIMES="libcxx;libcxxabi"``. 77 78 * ``-DCMAKE_INSTALL_PREFIX=directory`` --- Specify for *directory* the full 79 path name of where you want the LLVM tools and libraries to be installed 80 (default ``/usr/local``). Be careful if you install runtime libraries: if 81 your system uses those provided by LLVM (like libc++ or libc++abi), you 82 must not overwrite your system's copy of those libraries, since that 83 could render your system unusable. In general, using something like 84 ``/usr`` is not advised, but ``/usr/local`` is fine. 85 86 * ``-DCMAKE_BUILD_TYPE=type`` --- Valid options for *type* are Debug, 87 Release, RelWithDebInfo, and MinSizeRel. Default is Debug. 88 89 * ``-DLLVM_ENABLE_ASSERTIONS=On`` --- Compile with assertion checks enabled 90 (default is Yes for Debug builds, No for all other build types). 91 92 * ``cmake --build build [-- [options] <target>]`` or your build system specified above 93 directly. 94 95 * The default target (i.e. ``ninja`` or ``make``) will build all of LLVM. 96 97 * The ``check-all`` target (i.e. ``ninja check-all``) will run the 98 regression tests to ensure everything is in working order. 99 100 * CMake will generate targets for each tool and library, and most 101 LLVM sub-projects generate their own ``check-<project>`` target. 102 103 * Running a serial build will be **slow**. To improve speed, try running a 104 parallel build. That's done by default in Ninja; for ``make``, use the option 105 ``-j NNN``, where ``NNN`` is the number of parallel jobs, e.g. the number of 106 CPUs you have. 107 108 * For more information see [CMake](https://llvm.org/docs/CMake.html) 109 110Consult the 111[Getting Started with LLVM](https://llvm.org/docs/GettingStarted.html#getting-started-with-llvm) 112page for detailed information on configuring and compiling LLVM. You can visit 113[Directory Layout](https://llvm.org/docs/GettingStarted.html#directory-layout) 114to learn about the layout of the source code tree. 115 116## Getting in touch 117 118Join [LLVM Discourse forums](https://discourse.llvm.org/), [discord chat](https://discord.gg/xS7Z362) or #llvm IRC channel on [OFTC](https://oftc.net/). 119 120The LLVM project has adopted a [code of conduct](https://llvm.org/docs/CodeOfConduct.html) for 121participants to all modes of communication within the project. 122