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How to build LLVM, libclang, and liblld from source
Install CMake, version 3.15.3 or newer.
Download llvm, clang, and lld and unzip each to their own directory. Ensure no directories have spaces in them. For example:
C:\Users\Andy\llvm-12.0.0.srcC:\Users\Andy\clang-12.0.0.srcC:\Users\Andy\lld-12.0.0.src
Install Build Tools for Visual Studio 2019. Be sure to select "C++ build tools" when prompted.
- You must additionally check the optional component labeled C++ ATL for v142 build tools.
- Full list of supported MSVC versions:
- 2017 (version 15.8)
- 2019 (version 16)
Install Python 3.9.4. Tick the box to add python to your PATH environment variable.
Install CMake 3.17.
Using the start menu, run x64 Native Tools Command Prompt for VS 2019 and execute these commands, replacing C:\Users\Andy with the correct value.
mkdir C:\Users\Andy\llvm-12.0.0.src\build-release
cd C:\Users\Andy\llvm-12.0.0.src\build-release
"c:\Program Files\CMake\bin\cmake.exe" .. -Thost=x64 -G "Visual Studio 16 2019" -A x64 -DCMAKE_INSTALL_PREFIX=C:\Users\Andy\llvm+clang+lld-12.0.0-x86_64-windows-msvc-release-mt -DCMAKE_PREFIX_PATH=C:\Users\Andy\llvm+clang+lld-12.0.0-x86_64-windows-msvc-release-mt -DCMAKE_BUILD_TYPE=Release -DLLVM_ENABLE_LIBXML2=OFF -DLLVM_USE_CRT_RELEASE=MT
msbuild /m -p:Configuration=Release INSTALL.vcxprojmkdir C:\Users\Andy\llvm-12.0.0.src\build-debug
cd C:\Users\Andy\llvm-12.0.0.src\build-debug
"c:\Program Files\CMake\bin\cmake.exe" .. -Thost=x64 -G "Visual Studio 16 2019" -A x64 -DCMAKE_INSTALL_PREFIX=C:\Users\andy\llvm+clang+lld-12.0.0-x86_64-windows-msvc-debug -DCMAKE_PREFIX_PATH=C:\Users\andy\llvm+clang+lld-12.0.0-x86_64-windows-msvc-debug -DCMAKE_BUILD_TYPE=Debug -DLLVM_EXPERIMENTAL_TARGETS_TO_BUILD="AVR" -DLLVM_ENABLE_LIBXML2=OFF -DLLVM_USE_CRT_DEBUG=MTd
msbuild /m INSTALL.vcxprojUsing the start menu, run x64 Native Tools Command Prompt for VS 2019 and execute these commands, replacing C:\Users\Andy with the correct value.
mkdir C:\Users\Andy\lld-12.0.0.src\build-release
cd C:\Users\Andy\lld-12.0.0.src\build-release
"c:\Program Files\CMake\bin\cmake.exe" .. -Thost=x64 -G "Visual Studio 16 2019" -A x64 -DCMAKE_INSTALL_PREFIX=C:\Users\Andy\llvm+clang+lld-12.0.0-x86_64-windows-msvc-release-mt -DCMAKE_PREFIX_PATH=C:\Users\Andy\llvm+clang+lld-12.0.0-x86_64-windows-msvc-release-mt -DCMAKE_BUILD_TYPE=Release -DLLVM_USE_CRT_RELEASE=MT
msbuild /m -p:Configuration=Release INSTALL.vcxprojmkdir C:\Users\Andy\lld-12.0.0.src\build-debug
cd C:\Users\Andy\lld-12.0.0.src\build-debug
"c:\Program Files\CMake\bin\cmake.exe" .. -Thost=x64 -G "Visual Studio 16 2019" -A x64 -DCMAKE_INSTALL_PREFIX=C:\Users\andy\llvm+clang+lld-12.0.0-x86_64-windows-msvc-debug -DCMAKE_PREFIX_PATH=C:\Users\andy\llvm+clang+lld-12.0.0-x86_64-windows-msvc-debug -DCMAKE_BUILD_TYPE=Debug -DLLVM_USE_CRT_DEBUG=MTd
msbuild /m INSTALL.vcxprojUsing the start menu, run x64 Native Tools Command Prompt for VS 2019 and execute these commands, replacing C:\Users\Andy with the correct value.
mkdir C:\Users\Andy\clang-12.0.0.src\build-release
cd C:\Users\Andy\clang-12.0.0.src\build-release
"c:\Program Files\CMake\bin\cmake.exe" .. -Thost=x64 -G "Visual Studio 16 2019" -A x64 -DCMAKE_INSTALL_PREFIX=C:\Users\Andy\llvm+clang+lld-12.0.0-x86_64-windows-msvc-release-mt -DCMAKE_PREFIX_PATH=C:\Users\Andy\llvm+clang+lld-12.0.0-x86_64-windows-msvc-release-mt -DCMAKE_BUILD_TYPE=Release -DLLVM_USE_CRT_RELEASE=MT
msbuild /m -p:Configuration=Release INSTALL.vcxprojmkdir C:\Users\Andy\clang-12.0.0.src\build-debug
cd C:\Users\Andy\clang-12.0.0.src\build-debug
"c:\Program Files\CMake\bin\cmake.exe" .. -Thost=x64 -G "Visual Studio 16 2019" -A x64 -DCMAKE_INSTALL_PREFIX=C:\Users\andy\llvm+clang+lld-12.0.0-x86_64-windows-msvc-debug -DCMAKE_PREFIX_PATH=C:\Users\andy\llvm+clang+lld-12.0.0-x86_64-windows-msvc-debug -DCMAKE_BUILD_TYPE=Debug -DLLVM_USE_CRT_DEBUG=MTd
msbuild /m INSTALL.vcxprojTypically I use the path ~/local since it does not require root to install, and it's sandboxed away from the rest of my system. If there's garbage in that directory then I just wipe it and start over.
cd llvm-12.0.0.src/
mkdir build
cd build
cmake .. -DCMAKE_INSTALL_PREFIX=$HOME/local -DCMAKE_PREFIX_PATH=$HOME/local -DCMAKE_BUILD_TYPE=Release -DLLVM_ENABLE_LIBXML2=OFF
make installcd lld-12.0.0.src/
mkdir build
cd build
cmake .. -DCMAKE_INSTALL_PREFIX=$HOME/local -DCMAKE_PREFIX_PATH=$HOME/local -DCMAKE_BUILD_TYPE=Release
make installcd clang-12.0.0.src/
mkdir build
cd build
cmake .. -DCMAKE_INSTALL_PREFIX=$HOME/local -DCMAKE_PREFIX_PATH=$HOME/local -DCMAKE_BUILD_TYPE=Release
make installThen add to your zig cmake line that you got from the readme:
-DCMAKE_PREFIX_PATH=$HOME/local
If you get stuck you can look at the CI testing scripts for inspiration, keeping in mind that your environment might be different: https://github.com/ziglang/zig/tree/master/ci
Building LLVM has changed slightly since the release of LLVM 12, as LLVM now uses a monorepo. Instead of building llvm, clang and lld separately, they should now be build simultaneously:
$ ls
clang-12.0.0.src lld-12.0.0.src llvm-12.0.0.src
$ mkdir build
$ cd build
$ cmake ../llvm-12.0.0.src -DCMAKE_BUILD_TYPE=Release -DCMAKE_INSTALL_PREFIX=$HOME/local -DLLVM_ENABLE_PROJECTS="llvm-12.0.0.src;clang-12.0.0.src;lld-12.0.0.src"
$ make installNote that {llvm,clang,lld}-12.0.0.src in LLVM_ENABLE_PROJECTS simply refer to the directories placed alongside llvm-12.0.0.src.