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2 Getting Started with the LLVM System using Microsoft Visual Studio
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12 Welcome to LLVM on Windows! This document only covers LLVM on Windows using
13 Visual Studio, not WSL, mingw or cygwin. In order to get started, you first need
14 to know some basic information.
16 There are many different projects that compose LLVM. The first piece is the
17 LLVM suite. This contains all of the tools, libraries, and header files needed
18 to use LLVM. It contains an assembler, disassembler, bitcode analyzer and
19 bitcode optimizer. It also contains basic regression tests that can be used to
20 test the LLVM tools and the Clang front end.
22 The second piece is the `Clang <https://clang.llvm.org/>`_ front end. This
23 component compiles C, C++, Objective C, and Objective C++ code into LLVM
24 bitcode. Clang typically uses LLVM libraries to optimize the bitcode and emit
25 machine code. LLVM fully supports the COFF object file format, which is
26 compatible with all other existing Windows toolchains.
28 There are more LLVM projects which this document does not discuss.
33 Before you begin to use the LLVM system, review the requirements given
34 below. This may save you some trouble by knowing ahead of time what hardware
35 and software you will need.
39 Any system that can adequately run Visual Studio 2017 is fine. The LLVM
40 source tree including the git index consumes approximately 3GB.
41 Object files, libraries and executables consume approximately 5GB in
42 Release mode and much more in Debug mode. SSD drive and >16GB RAM are
48 You will need `Visual Studio <https://visualstudio.microsoft.com/>`_ 2017 or
49 higher, with the latest Update installed. Visual Studio Community Edition
52 You will also need the `CMake <http://www.cmake.org/>`_ build system since it
53 generates the project files you will use to build with. CMake is bundled with
54 Visual Studio 2019 so separate installation is not required.
56 If you would like to run the LLVM tests you will need `Python
57 <http://www.python.org/>`_. Version 3.6 and newer are known to work. You can
58 install Python with Visual Studio 2019, from the Microsoft store or from
59 the `Python web site <http://www.python.org/>`_. We recommend the latter since it
60 allows you to to adjust installation options.
62 You will need `Git for Windows <https://git-scm.com/>`_ with bash tools, too.
63 Git for Windows is also bundled with Visual Studio 2019.
68 Here's the short story for getting up and running quickly with LLVM.
69 These instruction were tested with Visual Studio 2019 and Python 3.9.6:
71 1. Download and install `Visual Studio <https://visualstudio.microsoft.com/>`_.
72 2. In the Visual Studio installer, Workloads tab, select the
73 **Desktop development with C++** workload. Under Individual components tab,
74 select **Git for Windows**.
75 3. Complete the Visual Studio installation.
76 4. Download and install the latest `Python 3 release <http://www.python.org/>`_.
77 5. In the first install screen, select both **Install launcher for all users**
78 and **Add Python to the PATH**. This will allow installing psutil for all
79 users for the regression tests and make Python available from the command
81 6. In the second install screen, select (again) **Install for all users** and
82 if you want to develop `lldb <https://lldb.llvm.org/>`_, selecting
83 **Download debug binaries** is useful.
84 7. Complete the Python installation.
85 8. Run a "Developer Command Prompt for VS 2019" **as administrator**. This command
86 prompt provides correct path and environment variables to Visual Studio and
88 9. In the terminal window, type the commands:
95 You may install the llvm sources in other location than ``c:\llvm`` but do not
96 install into a path containing spaces (e.g. ``c:\Documents and Settings\...``)
99 10. Register the Microsoft Debug Interface Access (DIA) DLLs
103 regsvr32 "%VSINSTALLDIR%\DIA SDK\bin\msdia140.dll"
104 regsvr32 "%VSINSTALLDIR%\DIA SDK\bin\amd64\msdia140.dll"
106 The DIA library is required for LLVM PDB tests and
107 `LLDB development <https://lldb.llvm.org/resources/build.html>`_.
109 11. Install psutil and obtain LLVM source code:
114 git clone https://github.com/llvm/llvm-project.git llvm
116 Instead of ``git clone`` you may download a compressed source distribution
117 from the `releases page <https://github.com/llvm/llvm-project/releases>`_.
118 Select the last link: ``Source code (zip)`` and unpack the downloaded file using
119 Windows Explorer built-in zip support or any other unzip tool.
121 12. Finally, configure LLVM using CMake:
125 cmake -S llvm\llvm -B build -DLLVM_ENABLE_PROJECTS=clang -DLLVM_TARGETS_TO_BUILD=X86 -Thost=x64
128 ``LLVM_ENABLE_PROJECTS`` specifies any additional LLVM projects you want to
129 build while ``LLVM_TARGETS_TO_BUILD`` selects the compiler targets. If
130 ``LLVM_TARGETS_TO_BUILD`` is omitted by default all targets are built
131 slowing compilation and using more disk space.
132 See the :doc:`LLVM CMake guide <CMake>` for detailed information about
133 how to configure the LLVM build.
135 The ``cmake`` command line tool is bundled with Visual Studio but its GUI is
136 not. You may install `CMake <http://www.cmake.org/>`_ to use its GUI to change
137 CMake variables or modify the above command line.
139 * Once CMake is installed then the simplest way is to just start the
140 CMake GUI, select the directory where you have LLVM extracted to, and
141 the default options should all be fine. One option you may really
142 want to change, regardless of anything else, might be the
143 ``CMAKE_INSTALL_PREFIX`` setting to select a directory to INSTALL to
144 once compiling is complete, although installation is not mandatory for
145 using LLVM. Another important option is ``LLVM_TARGETS_TO_BUILD``,
146 which controls the LLVM target architectures that are included on the
148 * CMake generates project files for all build types. To select a specific
149 build type, use the Configuration manager from the VS IDE or the
150 ``/property:Configuration`` command line option when using MSBuild.
151 * By default, the Visual Studio project files generated by CMake use the
152 32-bit toolset. If you are developing on a 64-bit version of Windows and
153 want to use the 64-bit toolset, pass the ``-Thost=x64`` flag when
154 generating the Visual Studio solution. This requires CMake 3.8.0 or later.
156 13. Start Visual Studio and select configuration:
158 In the directory you created the project files will have an ``llvm.sln``
159 file, just double-click on that to open Visual Studio. The default Visual
160 Studio configuration is **Debug** which is slow and generates a huge amount
161 of debug information on disk. For now, we recommend selecting **Release**
162 configuration for the LLVM project which will build the fastest or
163 **RelWithDebInfo** which is also several time larger than Release.
164 Another technique is to build all of LLVM in Release mode and change
165 compiler flags, disabling optimization and enabling debug information, only
166 for specific librares or source files you actually need to debug.
168 14. Test LLVM in Visual Studio:
170 You can run LLVM tests by merely building the project "check-all". The test
171 results will be shown in the VS output window. Once the build succeeds, you
172 have verified a working LLVM development environment!
174 You should not see any unexpected failures, but will see many unsupported
175 tests and expected failures:
179 114>Testing Time: 1124.66s
181 114> Unsupported : 21649
183 114> Expectedly Failed: 93
184 ========== Build: 114 succeeded, 0 failed, 321 up-to-date, 0 skipped ==========``
186 Alternatives to manual installation
187 ===================================
188 Instead of the steps above, to simplify the installation procedure you can use
189 `Chocolatey <https://chocolatey.org/>`_ as package manager.
190 After the `installation <https://chocolatey.org/install>`_ of Chocolatey,
191 run these commands in an admin shell to install the required tools:
195 choco install -y git cmake python3
198 There is also a Windows
199 `Dockerfile <https://github.com/llvm/llvm-zorg/blob/main/buildbot/google/docker/windows-base-vscode2019/Dockerfile>`_
200 with the entire build tool chain. This can be used to test the build with a
201 tool chain different from your host installation or to create build servers.
205 1. Read the documentation.
206 2. Seriously, read the documentation.
207 3. Remember that you were warned twice about reading the documentation.
209 Test LLVM on the command line:
210 ------------------------------
211 The LLVM tests can be run by changing directory to the llvm source
212 directory and running:
216 c:\llvm> python ..\build\Release\bin\llvm-lit.py llvm\test
218 This example assumes that Python is in your PATH variable, which would be
219 after **Add Python to the PATH** was selected during Python installation.
220 If you had opened a command window prior to Python installation, you would
221 have to close and reopen it to get the updated PATH.
223 A specific test or test directory can be run with:
227 c:\llvm> python ..\build\Release\bin\llvm-lit.py llvm\test\Transforms\Util
229 Build the LLVM Suite:
230 ---------------------
231 * The projects may still be built individually, but to build them all do
232 not just select all of them in batch build (as some are meant as
233 configuration projects), but rather select and build just the
234 ``ALL_BUILD`` project to build everything, or the ``INSTALL`` project,
235 which first builds the ``ALL_BUILD`` project, then installs the LLVM
236 headers, libs, and other useful things to the directory set by the
237 ``CMAKE_INSTALL_PREFIX`` setting when you first configured CMake.
238 * The Fibonacci project is a sample program that uses the JIT. Modify the
239 project's debugging properties to provide a numeric command line argument
240 or run it from the command line. The program will print the
241 corresponding fibonacci value.
246 This document is just an **introduction** to how to use LLVM to do some simple
247 things... there are many more interesting and complicated things that you can
248 do that aren't documented here (but we'll gladly accept a patch if you want to
249 write something up!). For more information about LLVM, check out:
251 * `LLVM homepage <https://llvm.org/>`_
252 * `LLVM doxygen tree <https://llvm.org/doxygen/>`_
253 * Additional information about the LLVM directory structure and tool chain
254 can be found on the main :doc:`GettingStarted` page.
255 * If you are having problems building or using LLVM, or if you have any other
256 general questions about LLVM, please consult the
257 :doc:`Frequently Asked Questions <FAQ>` page.