LLVM Embedded Toolchain is built and tested on Ubuntu 20.04 LTS.
The Windows version of LLVM tools is built on Windows Server 2019 and lightly tested on Windows 10. Windows package provides runtime libraries built on Linux, because of their limited Windows support.
Building and testing on macOS is functional but experimental.
The build requires the following software to be installed, in addition to the LLVM requirements:
- CMake 3.20 or above
- Meson
- Git
- Ninja
- Python
- QEMU (for running the test suite, so optional)
On a Ubuntu 18.04.5 LTS machine you can use the following commands to install the software mentioned above:
$ apt-get install python3 git make ninja-build qemu
$ apt-get install clang # If the Clang version installed by the package manager is older than 6.0.0, download a recent version from https://releases.llvm.org or build from source
$ apt-get install cmake # If the CMake version installed by the package manager is too old, download a recent version from https://cmake.org/download and add it to PATH
$ pip install meson
On macOS, you can use homebrew:
$ brew install llvm python3 git make ninja qemu cmake
$ pip install meson
To build additional library variants, edit the CMakeLists.txt by adding
calls to the add_library_variant CMake function using existing library
variant definitions as a template.
To build additional LLVM tools, edit the CMakeLists.txt by adding required
tools to the LLVM_DISTRIBUTION_COMPONENTS CMake list.
The toolchain can be built directly with CMake.
mkdir build
cd build
cmake .. -GNinja -DFETCHCONTENT_QUIET=OFF
ninja llvm-toolchain
To make it easy to get started, the above command checks out and patches llvm-project & picolibc Git repos automatically.
If you prefer you can check out and patch the repos manually and use those.
If you check out repos manually then it is your responsibility to ensure that the correct revisions are checked out - see versions.json to identify these.
mkdir repos
git -C repos clone https://github.com/llvm/llvm-project.git
git -C repos/llvm-project am -k "$PWD"/../patches/llvm-project/*.patch
git -C repos clone https://github.com/picolibc/picolibc.git
git -C repos/picolibc apply "$PWD"/../patches/picolibc.patch
mkdir build
cd build
cmake .. -GNinja -DFETCHCONTENT_SOURCE_DIR_LLVMPROJECT=../repos/llvm-project -DFETCHCONTENT_SOURCE_DIR_PICOLIBC=../repos/picolibc
ninja llvm-toolchain
ninja check-llvm-toolchain
After building, create a zip or tar.xz file as appropriate for the platform:
ninja package-llvm-toolchain
The LLVM Embedded Toolchain can be cross-compiled to run on Windows. The compilation itself still happens on Linux. In addition to the prerequisites mentioned in the Installing prerequisites section you will also need a Mingw-w64 toolchain based on GCC 7.1.0 or above installed. For example, to install it on Ubuntu Linux use the following command:
# apt-get install mingw-w64
The MinGW build includes GCC & MinGW libraries into the package.
The following three libraries are used:
| Library | Project | Link |
|---|---|---|
| libstdc++-6.dll | GCC | https://gcc.gnu.org |
| libgcc_s_seh-1.dll | GCC | https://gcc.gnu.org |
| libwinpthread-1.dll | Mingw-w64 | http://mingw-w64.org |
The libraries are distributed under their own licenses, this needs to be taken into consideration if you decide to redistribute the built toolchain.
To enable the MinGW build, set the LLVM_TOOLCHAIN_CROSS_BUILD_MINGW option:
cmake . -DLLVM_TOOLCHAIN_CROSS_BUILD_MINGW=ON
ninja package-llvm-toolchain
The same build directory can be used for both native and MinGW toolchains.
- Depending on the state of the sources, build errors may occur when the latest revisions of the llvm-project & picolibc repos are used.
See patches directory for the current set of differences from upstream.