1================================================================== 2Getting Started with the LLVM System using Microsoft Visual Studio 3================================================================== 4 5 6.. contents:: 7 :local: 8 9 10Overview 11======== 12Welcome to LLVM on Windows! This document only covers LLVM on Windows using 13Visual Studio, not WSL, mingw or cygwin. In order to get started, you first need 14to know some basic information. 15 16There are many different projects that compose LLVM. The first piece is the 17LLVM suite. This contains all of the tools, libraries, and header files needed 18to use LLVM. It contains an assembler, disassembler, bitcode analyzer and 19bitcode optimizer. It also contains basic regression tests that can be used to 20test the LLVM tools and the Clang front end. 21 22The second piece is the `Clang <https://clang.llvm.org/>`_ front end. This 23component compiles C, C++, Objective C, and Objective C++ code into LLVM 24bitcode. Clang typically uses LLVM libraries to optimize the bitcode and emit 25machine code. LLVM fully supports the COFF object file format, which is 26compatible with all other existing Windows toolchains. 27 28There are more LLVM projects which this document does not discuss. 29 30 31Requirements 32============ 33Before you begin to use the LLVM system, review the requirements given 34below. This may save you some trouble by knowing ahead of time what hardware 35and software you will need. 36 37Hardware 38-------- 39Any system that can adequately run Visual Studio 2019 is fine. The LLVM 40source tree including the git index consumes approximately 3GB. 41Object files, libraries and executables consume approximately 5GB in 42Release mode and much more in Debug mode. SSD drive and >16GB RAM are 43recommended. 44 45 46Software 47-------- 48You will need `Visual Studio <https://visualstudio.microsoft.com/>`_ 2019 or 49later, with the latest Update installed. Visual Studio Community Edition 50suffices. 51 52You will also need the `CMake <http://www.cmake.org/>`_ build system since it 53generates the project files you will use to build with. CMake is bundled with 54Visual Studio 2019 so separate installation is not required. If you do install 55CMake separately, Visual Studio 2022 will require CMake Version 3.21 or later. 56 57If you would like to run the LLVM tests you will need `Python 58<http://www.python.org/>`_. Version 3.8 and newer are known to work. You can 59install Python with Visual Studio 2019, from the Microsoft store or from 60the `Python web site <http://www.python.org/>`_. We recommend the latter since it 61allows you to adjust installation options. 62 63You will need `Git for Windows <https://git-scm.com/>`_ with bash tools, too. 64Git for Windows is also bundled with Visual Studio 2019. 65 66 67Getting Started 68=============== 69Here's the short story for getting up and running quickly with LLVM. 70These instruction were tested with Visual Studio 2019 and Python 3.9.6: 71 721. Download and install `Visual Studio <https://visualstudio.microsoft.com/>`_. 732. In the Visual Studio installer, Workloads tab, select the 74 **Desktop development with C++** workload. Under Individual components tab, 75 select **Git for Windows**. 763. Complete the Visual Studio installation. 774. Download and install the latest `Python 3 release <http://www.python.org/>`_. 785. In the first install screen, select both **Install launcher for all users** 79 and **Add Python to the PATH**. This will allow installing psutil for all 80 users for the regression tests and make Python available from the command 81 line. 826. In the second install screen, select (again) **Install for all users** and 83 if you want to develop `lldb <https://lldb.llvm.org/>`_, selecting 84 **Download debug binaries** is useful. 857. Complete the Python installation. 868. Run a "Developer Command Prompt for VS 2019" **as administrator**. This command 87 prompt provides correct path and environment variables to Visual Studio and 88 the installed tools. 899. In the terminal window, type the commands: 90 91 .. code-block:: bat 92 93 c: 94 cd \ 95 96 You may install the llvm sources in other location than ``c:\llvm`` but do not 97 install into a path containing spaces (e.g. ``c:\Documents and Settings\...``) 98 as it will fail. 99 10010. Register the Microsoft Debug Interface Access (DIA) DLLs 101 102 .. code-block:: bat 103 104 regsvr32 "%VSINSTALLDIR%\DIA SDK\bin\msdia140.dll" 105 regsvr32 "%VSINSTALLDIR%\DIA SDK\bin\amd64\msdia140.dll" 106 107 The DIA library is required for LLVM PDB tests and 108 `LLDB development <https://lldb.llvm.org/resources/build.html>`_. 109 11011. Install psutil and obtain LLVM source code: 111 112 .. code-block:: bat 113 114 pip install psutil 115 git clone https://github.com/llvm/llvm-project.git llvm 116 117 Instead of ``git clone`` you may download a compressed source distribution 118 from the `releases page <https://github.com/llvm/llvm-project/releases>`_. 119 Select the last link: ``Source code (zip)`` and unpack the downloaded file using 120 Windows Explorer built-in zip support or any other unzip tool. 121 12212. Finally, configure LLVM using CMake: 123 124 .. code-block:: bat 125 126 cmake -S llvm\llvm -B build -DLLVM_ENABLE_PROJECTS=clang -DLLVM_TARGETS_TO_BUILD=X86 -Thost=x64 127 exit 128 129 ``LLVM_ENABLE_PROJECTS`` specifies any additional LLVM projects you want to 130 build while ``LLVM_TARGETS_TO_BUILD`` selects the compiler targets. If 131 ``LLVM_TARGETS_TO_BUILD`` is omitted by default all targets are built 132 slowing compilation and using more disk space. 133 See the :doc:`LLVM CMake guide <CMake>` for detailed information about 134 how to configure the LLVM build. 135 136 The ``cmake`` command line tool is bundled with Visual Studio but its GUI is 137 not. You may install `CMake <http://www.cmake.org/>`_ to use its GUI to change 138 CMake variables or modify the above command line. 139 140 * Once CMake is installed then the simplest way is to just start the 141 CMake GUI, select the directory where you have LLVM extracted to, and 142 the default options should all be fine. One option you may really 143 want to change, regardless of anything else, might be the 144 ``CMAKE_INSTALL_PREFIX`` setting to select a directory to INSTALL to 145 once compiling is complete, although installation is not mandatory for 146 using LLVM. Another important option is ``LLVM_TARGETS_TO_BUILD``, 147 which controls the LLVM target architectures that are included on the 148 build. 149 * CMake generates project files for all build types. To select a specific 150 build type, use the Configuration manager from the VS IDE or the 151 ``/property:Configuration`` command line option when using MSBuild. 152 * By default, the Visual Studio project files generated by CMake use the 153 32-bit toolset. If you are developing on a 64-bit version of Windows and 154 want to use the 64-bit toolset, pass the ``-Thost=x64`` flag when 155 generating the Visual Studio solution. This requires CMake 3.8.0 or later. 156 15713. Start Visual Studio and select configuration: 158 159 In the directory you created the project files will have an ``llvm.sln`` 160 file, just double-click on that to open Visual Studio. The default Visual 161 Studio configuration is **Debug** which is slow and generates a huge amount 162 of debug information on disk. For now, we recommend selecting **Release** 163 configuration for the LLVM project which will build the fastest or 164 **RelWithDebInfo** which is also several time larger than Release. 165 Another technique is to build all of LLVM in Release mode and change 166 compiler flags, disabling optimization and enabling debug information, only 167 for specific libraries or source files you actually need to debug. 168 16914. Test LLVM in Visual Studio: 170 171 You can run LLVM tests by merely building the project "check-all". The test 172 results will be shown in the VS output window. Once the build succeeds, you 173 have verified a working LLVM development environment! 174 175 You should not see any unexpected failures, but will see many unsupported 176 tests and expected failures: 177 178 :: 179 180 114>Testing Time: 1124.66s 181 114> Skipped : 39 182 114> Unsupported : 21649 183 114> Passed : 51615 184 114> Expectedly Failed: 93 185 ========== Build: 114 succeeded, 0 failed, 321 up-to-date, 0 skipped ==========`` 186 187Alternatives to manual installation 188=================================== 189Instead of the steps above, to simplify the installation procedure you can use 190`Chocolatey <https://chocolatey.org/>`_ as package manager. 191After the `installation <https://chocolatey.org/install>`_ of Chocolatey, 192run these commands in an admin shell to install the required tools: 193 194.. code-block:: bat 195 196 choco install -y git cmake python3 197 pip3 install psutil 198 199There is also a Windows 200`Dockerfile <https://github.com/llvm/llvm-zorg/blob/main/buildbot/google/docker/windows-base-vscode2019/Dockerfile>`_ 201with the entire build tool chain. This can be used to test the build with a 202tool chain different from your host installation or to create build servers. 203 204Next steps 205========== 2061. Read the documentation. 2072. Seriously, read the documentation. 2083. Remember that you were warned twice about reading the documentation. 209 210Test LLVM on the command line: 211------------------------------ 212The LLVM tests can be run by changing directory to the llvm source 213directory and running: 214 215.. code-block:: bat 216 217 c:\llvm> python ..\build\Release\bin\llvm-lit.py llvm\test 218 219This example assumes that Python is in your PATH variable, which would be 220after **Add Python to the PATH** was selected during Python installation. 221If you had opened a command window prior to Python installation, you would 222have to close and reopen it to get the updated PATH. 223 224A specific test or test directory can be run with: 225 226.. code-block:: bat 227 228 c:\llvm> python ..\build\Release\bin\llvm-lit.py llvm\test\Transforms\Util 229 230Build the LLVM Suite: 231--------------------- 232* The projects may still be built individually, but to build them all do 233 not just select all of them in batch build (as some are meant as 234 configuration projects), but rather select and build just the 235 ``ALL_BUILD`` project to build everything, or the ``INSTALL`` project, 236 which first builds the ``ALL_BUILD`` project, then installs the LLVM 237 headers, libs, and other useful things to the directory set by the 238 ``CMAKE_INSTALL_PREFIX`` setting when you first configured CMake. 239* The Fibonacci project is a sample program that uses the JIT. Modify the 240 project's debugging properties to provide a numeric command line argument 241 or run it from the command line. The program will print the 242 corresponding fibonacci value. 243 244 245Links 246===== 247This document is just an **introduction** to how to use LLVM to do some simple 248things... there are many more interesting and complicated things that you can 249do that aren't documented here (but we'll gladly accept a patch if you want to 250write something up!). For more information about LLVM, check out: 251 252* `LLVM homepage <https://llvm.org/>`_ 253* `LLVM doxygen tree <https://llvm.org/doxygen/>`_ 254* Additional information about the LLVM directory structure and tool chain 255 can be found on the main :doc:`GettingStarted` page. 256* If you are having problems building or using LLVM, or if you have any other 257 general questions about LLVM, please consult the 258 :doc:`Frequently Asked Questions <FAQ>` page. 259