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259 lines
11 KiB
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==================================================================
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Getting Started with the LLVM System using Microsoft Visual Studio
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==================================================================
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.. contents::
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:local:
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Overview
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========
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Welcome to LLVM on Windows! This document only covers LLVM on Windows using
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Visual Studio, not WSL, mingw or cygwin. In order to get started, you first need
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to know some basic information.
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There are many different projects that compose LLVM. The first piece is the
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LLVM suite. This contains all of the tools, libraries, and header files needed
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to use LLVM. It contains an assembler, disassembler, bitcode analyzer and
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bitcode optimizer. It also contains basic regression tests that can be used to
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test the LLVM tools and the Clang front end.
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The second piece is the `Clang <https://clang.llvm.org/>`_ front end. This
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component compiles C, C++, Objective C, and Objective C++ code into LLVM
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bitcode. Clang typically uses LLVM libraries to optimize the bitcode and emit
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machine code. LLVM fully supports the COFF object file format, which is
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compatible with all other existing Windows toolchains.
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There are more LLVM projects which this document does not discuss.
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Requirements
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============
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Before you begin to use the LLVM system, review the requirements given
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below. This may save you some trouble by knowing ahead of time what hardware
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and software you will need.
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Hardware
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--------
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Any system that can adequately run Visual Studio 2019 is fine. The LLVM
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source tree including the git index consumes approximately 3GB.
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Object files, libraries and executables consume approximately 5GB in
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Release mode and much more in Debug mode. SSD drive and >16GB RAM are
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recommended.
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Software
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--------
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You will need `Visual Studio <https://visualstudio.microsoft.com/>`_ 2019 or
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later, with the latest Update installed. Visual Studio Community Edition
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suffices.
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You will also need the `CMake <http://www.cmake.org/>`_ build system since it
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generates the project files you will use to build with. CMake is bundled with
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Visual Studio 2019 so separate installation is not required. If you do install
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CMake separately, Visual Studio 2022 will require CMake Version 3.21 or later.
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If you would like to run the LLVM tests you will need `Python
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<http://www.python.org/>`_. Version 3.6 and newer are known to work. You can
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install Python with Visual Studio 2019, from the Microsoft store or from
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the `Python web site <http://www.python.org/>`_. We recommend the latter since it
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allows you to to adjust installation options.
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You will need `Git for Windows <https://git-scm.com/>`_ with bash tools, too.
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Git for Windows is also bundled with Visual Studio 2019.
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Getting Started
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===============
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Here's the short story for getting up and running quickly with LLVM.
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These instruction were tested with Visual Studio 2019 and Python 3.9.6:
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1. Download and install `Visual Studio <https://visualstudio.microsoft.com/>`_.
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2. In the Visual Studio installer, Workloads tab, select the
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**Desktop development with C++** workload. Under Individual components tab,
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select **Git for Windows**.
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3. Complete the Visual Studio installation.
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4. Download and install the latest `Python 3 release <http://www.python.org/>`_.
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5. In the first install screen, select both **Install launcher for all users**
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and **Add Python to the PATH**. This will allow installing psutil for all
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users for the regression tests and make Python available from the command
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line.
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6. In the second install screen, select (again) **Install for all users** and
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if you want to develop `lldb <https://lldb.llvm.org/>`_, selecting
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**Download debug binaries** is useful.
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7. Complete the Python installation.
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8. Run a "Developer Command Prompt for VS 2019" **as administrator**. This command
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prompt provides correct path and environment variables to Visual Studio and
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the installed tools.
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9. In the terminal window, type the commands:
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.. code-block:: bat
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c:
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cd \
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You may install the llvm sources in other location than ``c:\llvm`` but do not
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install into a path containing spaces (e.g. ``c:\Documents and Settings\...``)
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as it will fail.
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10. Register the Microsoft Debug Interface Access (DIA) DLLs
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.. code-block:: bat
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regsvr32 "%VSINSTALLDIR%\DIA SDK\bin\msdia140.dll"
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regsvr32 "%VSINSTALLDIR%\DIA SDK\bin\amd64\msdia140.dll"
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The DIA library is required for LLVM PDB tests and
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`LLDB development <https://lldb.llvm.org/resources/build.html>`_.
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11. Install psutil and obtain LLVM source code:
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.. code-block:: bat
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pip install psutil
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git clone https://github.com/llvm/llvm-project.git llvm
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Instead of ``git clone`` you may download a compressed source distribution
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from the `releases page <https://github.com/llvm/llvm-project/releases>`_.
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Select the last link: ``Source code (zip)`` and unpack the downloaded file using
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Windows Explorer built-in zip support or any other unzip tool.
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12. Finally, configure LLVM using CMake:
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.. code-block:: bat
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cmake -S llvm\llvm -B build -DLLVM_ENABLE_PROJECTS=clang -DLLVM_TARGETS_TO_BUILD=X86 -Thost=x64
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exit
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``LLVM_ENABLE_PROJECTS`` specifies any additional LLVM projects you want to
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build while ``LLVM_TARGETS_TO_BUILD`` selects the compiler targets. If
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``LLVM_TARGETS_TO_BUILD`` is omitted by default all targets are built
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slowing compilation and using more disk space.
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See the :doc:`LLVM CMake guide <CMake>` for detailed information about
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how to configure the LLVM build.
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The ``cmake`` command line tool is bundled with Visual Studio but its GUI is
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not. You may install `CMake <http://www.cmake.org/>`_ to use its GUI to change
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CMake variables or modify the above command line.
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* Once CMake is installed then the simplest way is to just start the
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CMake GUI, select the directory where you have LLVM extracted to, and
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the default options should all be fine. One option you may really
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want to change, regardless of anything else, might be the
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``CMAKE_INSTALL_PREFIX`` setting to select a directory to INSTALL to
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once compiling is complete, although installation is not mandatory for
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using LLVM. Another important option is ``LLVM_TARGETS_TO_BUILD``,
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which controls the LLVM target architectures that are included on the
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build.
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* CMake generates project files for all build types. To select a specific
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build type, use the Configuration manager from the VS IDE or the
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``/property:Configuration`` command line option when using MSBuild.
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* By default, the Visual Studio project files generated by CMake use the
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32-bit toolset. If you are developing on a 64-bit version of Windows and
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want to use the 64-bit toolset, pass the ``-Thost=x64`` flag when
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generating the Visual Studio solution. This requires CMake 3.8.0 or later.
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13. Start Visual Studio and select configuration:
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In the directory you created the project files will have an ``llvm.sln``
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file, just double-click on that to open Visual Studio. The default Visual
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Studio configuration is **Debug** which is slow and generates a huge amount
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of debug information on disk. For now, we recommend selecting **Release**
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configuration for the LLVM project which will build the fastest or
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**RelWithDebInfo** which is also several time larger than Release.
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Another technique is to build all of LLVM in Release mode and change
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compiler flags, disabling optimization and enabling debug information, only
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for specific librares or source files you actually need to debug.
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14. Test LLVM in Visual Studio:
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You can run LLVM tests by merely building the project "check-all". The test
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results will be shown in the VS output window. Once the build succeeds, you
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have verified a working LLVM development environment!
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You should not see any unexpected failures, but will see many unsupported
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tests and expected failures:
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::
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114>Testing Time: 1124.66s
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114> Skipped : 39
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114> Unsupported : 21649
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114> Passed : 51615
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114> Expectedly Failed: 93
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========== Build: 114 succeeded, 0 failed, 321 up-to-date, 0 skipped ==========``
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Alternatives to manual installation
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===================================
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Instead of the steps above, to simplify the installation procedure you can use
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`Chocolatey <https://chocolatey.org/>`_ as package manager.
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After the `installation <https://chocolatey.org/install>`_ of Chocolatey,
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run these commands in an admin shell to install the required tools:
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.. code-block:: bat
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choco install -y git cmake python3
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pip3 install psutil
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There is also a Windows
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`Dockerfile <https://github.com/llvm/llvm-zorg/blob/main/buildbot/google/docker/windows-base-vscode2019/Dockerfile>`_
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with the entire build tool chain. This can be used to test the build with a
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tool chain different from your host installation or to create build servers.
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Next steps
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==========
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1. Read the documentation.
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2. Seriously, read the documentation.
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3. Remember that you were warned twice about reading the documentation.
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Test LLVM on the command line:
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------------------------------
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The LLVM tests can be run by changing directory to the llvm source
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directory and running:
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.. code-block:: bat
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c:\llvm> python ..\build\Release\bin\llvm-lit.py llvm\test
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This example assumes that Python is in your PATH variable, which would be
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after **Add Python to the PATH** was selected during Python installation.
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If you had opened a command window prior to Python installation, you would
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have to close and reopen it to get the updated PATH.
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A specific test or test directory can be run with:
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.. code-block:: bat
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c:\llvm> python ..\build\Release\bin\llvm-lit.py llvm\test\Transforms\Util
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Build the LLVM Suite:
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---------------------
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* The projects may still be built individually, but to build them all do
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not just select all of them in batch build (as some are meant as
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configuration projects), but rather select and build just the
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``ALL_BUILD`` project to build everything, or the ``INSTALL`` project,
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which first builds the ``ALL_BUILD`` project, then installs the LLVM
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headers, libs, and other useful things to the directory set by the
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``CMAKE_INSTALL_PREFIX`` setting when you first configured CMake.
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* The Fibonacci project is a sample program that uses the JIT. Modify the
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project's debugging properties to provide a numeric command line argument
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or run it from the command line. The program will print the
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corresponding fibonacci value.
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Links
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=====
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This document is just an **introduction** to how to use LLVM to do some simple
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things... there are many more interesting and complicated things that you can
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do that aren't documented here (but we'll gladly accept a patch if you want to
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write something up!). For more information about LLVM, check out:
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* `LLVM homepage <https://llvm.org/>`_
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* `LLVM doxygen tree <https://llvm.org/doxygen/>`_
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* Additional information about the LLVM directory structure and tool chain
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can be found on the main :doc:`GettingStarted` page.
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* If you are having problems building or using LLVM, or if you have any other
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general questions about LLVM, please consult the
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:doc:`Frequently Asked Questions <FAQ>` page.
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