LLVM is huge, and it's getting bigger with each and every release. Building it together with a project that depends on it (e.g., a programming language) during a CI build is not an option -- building just LLVM eats most (earlier LLVM releases), and all (recent LLVM releases) of the allotted CI build time.

So why not use pre-built packages from the official LLVM download page? Unfortunately, the official binaries cover just a tiny fraction of possible build configurations on Microsoft Windows. There are no Debug libraries, no builds for the static LIBCMT, and only a single toolchain per LLVM release.

The llvm-package-windows project builds all major versions of LLVM on GitHub Actions for the following, much more complete matrix:

• Toolchain:

  • Visual Studio 2017
  • Visual Studio 2015 (LLVM 3.4.2 to 8.0.0)
  • Visual Studio 2013 (LLVM 3.4.2 to 3.9.1)
  • Visual Studio 2010 (LLVM 3.4.2 only)

• Configuration:

  • Debug
  • Release

• Target CPU:

  • IA32 (a.k.a. x86)
  • AMD64 (a.k.a. x86_64)

• C/C++ Runtime:

  • LIBCMT (static)
  • MSVCRT (dynamic)

The resulting LLVM binary packages are uploaded as GitHub Release artifacts. Compiler developers can now thoroughly test their LLVM-dependent projects on GitHub CI or AppVeyor CI simply by downloading and unpacking an archive with the required LLVM prebuilt binaries during the CI installation stage.

• Jancy uses llvm-package-windows for CI testing on a range of configurations and LLVM versions. See build logs for more details.