• OpenBLAS can be built from source for WoA using LLVM toolchain (clang-cl and flang)

• Installer available for v3.30 onwards (https://github.com/OpenMathLib/OpenBLAS/releases/tag/v0.3.30 )

Requirements

• LLVM >= 17.0.4
  (<= 16 emits conflicting symbols_QQ*, <= 17.0.3 mlir conflicting symbol)

• CMake >= 3.28 (previous version fail with flang targeting MSVC ABI)

Build Steps

• Clone OpenBLAS from https://github.com/OpenMathLib/OpenBLAS

  git clone https://github.com/OpenMathLib/OpenBLAS cd OpenBLAS mkdir build cd build cmake .. -G Ninja -DCMAKE_C_COMPILER=clang-cl -DCMAKE_Fortran_COMPILER=flang-new -DBUILD_SHARED_LIBS=TRUE -DCMAKE_BUILD_TYPE=Release ninja

• https://github.com/xianyi/OpenBLAS/pull/3345

• https://github.com/xianyi/OpenBLAS/pull/3354

• https://gitlab.kitware.com/cmake/cmake/-/merge_requests/8852

• LLVM 17.0.4 fix: https://github.com/llvm/llvm-project-release-prs/pull/752

OpenBLAS has to be built from source for windows-arm64. https://github.com/OpenMathLib/OpenBLAS/releases/tag/v0.3.30

There is no official windows-arm64 CI running for OpenBLAS, due to lack of machines on GitHub Actions. We run a downstream nightly CI (building develop branch and running tests) on our infrastructure: https://gitlab.com/Linaro/windowsonarm/nightly.