1# The LLVM Compiler Infrastructure 2 3This directory and its subdirectories contain source code for LLVM, 4a toolkit for the construction of highly optimized compilers, 5optimizers, and runtime environments. 6 7## Getting Started with the LLVM System 8 9Taken from https://llvm.org/docs/GettingStarted.html. 10 11### Overview 12 13Welcome to the LLVM project! 14 15The LLVM project has multiple components. The core of the project is 16itself called "LLVM". This contains all of the tools, libraries, and header 17files needed to process intermediate representations and converts it into 18object files. Tools include an assembler, disassembler, bitcode analyzer, and 19bitcode optimizer. It also contains basic regression tests. 20 21C-like languages use the [Clang](http://clang.llvm.org/) front end. This 22component compiles C, C++, Objective C, and Objective C++ code into LLVM bitcode 23-- and from there into object files, using LLVM. 24 25Other components include: 26the [libc++ C++ standard library](https://libcxx.llvm.org), 27the [LLD linker](https://lld.llvm.org), and more. 28 29### Getting the Source Code and Building LLVM 30 31The LLVM Getting Started documentation may be out of date. The [Clang 32Getting Started](http://clang.llvm.org/get_started.html) page might have more 33accurate information. 34 35This is an example workflow and configuration to get and build the LLVM source: 36 371. Checkout LLVM (including related subprojects like Clang): 38 39 * ``git clone https://github.com/llvm/llvm-project.git`` 40 41 * Or, on windows, ``git clone --config core.autocrlf=false 42 https://github.com/llvm/llvm-project.git`` 43 442. Configure and build LLVM and Clang: 45 46 * ``cd llvm-project`` 47 48 * ``mkdir build`` 49 50 * ``cd build`` 51 52 * ``cmake -G <generator> [options] ../llvm`` 53 54 Some common generators are: 55 56 * ``Ninja`` --- for generating [Ninja](https://ninja-build.org) 57 build files. Most llvm developers use Ninja. 58 * ``Unix Makefiles`` --- for generating make-compatible parallel makefiles. 59 * ``Visual Studio`` --- for generating Visual Studio projects and 60 solutions. 61 * ``Xcode`` --- for generating Xcode projects. 62 63 Some Common options: 64 65 * ``-DLLVM_ENABLE_PROJECTS='...'`` --- semicolon-separated list of the LLVM 66 subprojects you'd like to additionally build. Can include any of: clang, 67 clang-tools-extra, libcxx, libcxxabi, libunwind, lldb, compiler-rt, lld, 68 polly, or debuginfo-tests. 69 70 For example, to build LLVM, Clang, libcxx, and libcxxabi, use 71 ``-DLLVM_ENABLE_PROJECTS="clang;libcxx;libcxxabi"``. 72 73 * ``-DCMAKE_INSTALL_PREFIX=directory`` --- Specify for *directory* the full 74 pathname of where you want the LLVM tools and libraries to be installed 75 (default ``/usr/local``). 76 77 * ``-DCMAKE_BUILD_TYPE=type`` --- Valid options for *type* are Debug, 78 Release, RelWithDebInfo, and MinSizeRel. Default is Debug. 79 80 * ``-DLLVM_ENABLE_ASSERTIONS=On`` --- Compile with assertion checks enabled 81 (default is Yes for Debug builds, No for all other build types). 82 83 * Run your build tool of choice! 84 85 * The default target (i.e. ``ninja`` or ``make``) will build all of LLVM. 86 87 * The ``check-all`` target (i.e. ``ninja check-all``) will run the 88 regression tests to ensure everything is in working order. 89 90 * CMake will generate build targets for each tool and library, and most 91 LLVM sub-projects generate their own ``check-<project>`` target. 92 93 * Running a serial build will be *slow*. To improve speed, try running a 94 parallel build. That's done by default in Ninja; for ``make``, use 95 ``make -j NNN`` (NNN is the number of parallel jobs, use e.g. number of 96 CPUs you have.) 97 98 * For more information see [CMake](https://llvm.org/docs/CMake.html) 99 100Consult the 101[Getting Started with LLVM](https://llvm.org/docs/GettingStarted.html#getting-started-with-llvm) 102page for detailed information on configuring and compiling LLVM. You can visit 103[Directory Layout](https://llvm.org/docs/GettingStarted.html#directory-layout) 104to learn about the layout of the source code tree. 105