Windows CI (#3021)

.github/actions/build-windows/action.yml

@@ -0,0 +1,18 @@
+name: 'Build on Windows'
+
+runs:
+  using: 'composite'
+  steps:
+    - name: Build CPP only
+      shell: cmd
+      env:
+        # For MSVC, Ninja/Release is the only config supported by ccache.
+        CMAKE_ARGS: >-
+          -G Ninja
+          -DCMAKE_BUILD_TYPE=Release
+          -DCMAKE_C_COMPILER=cl
+          -DCMAKE_CXX_COMPILER=cl
+          -DCMAKE_RC_COMPILER=rc
+      run: |
+        cmake . -B build %CMAKE_ARGS%
+        cmake --build build -j %NUMBER_OF_PROCESSORS%

.github/actions/setup-windows/action.yml

@@ -0,0 +1,37 @@
+name: 'Setup Windows environment'
+
+inputs:
+  python-version:
+    description: 'Version of python to set up'
+    required: false
+    default: '3.14'
+  use-ccache:
+    description: 'Whether to enable ccache'
+    required: false
+    default: 'true'
+
+runs:
+  using: 'composite'
+  steps:
+    - name: Use ccache
+      if: ${{ inputs.use-ccache == 'true' }}
+      uses: hendrikmuhs/[email protected]
+      with:
+        key: ccache-${{ runner.os }}-${{ runner.arch }}-cpu
+        max-size: 1GB
+
+    - uses: actions/setup-python@v6
+      with:
+        python-version: ${{ inputs.python-version }}
+
+    - name: Setup Visual Studio cmd
+      shell: cmd
+      run: |
+        :: Find out path to VS.
+        pushd "C:\Program Files (x86)\Microsoft Visual Studio\Installer\"
+        for /f "delims=" %%x in ('.\vswhere.exe -latest -property InstallationPath') do set VSPATH=%%x
+        popd
+        :: Import VS vars.
+        call "%VSPATH%\VC\Auxiliary\Build\vcvarsall.bat" x64
+        :: Export to all steps.
+        >>%GITHUB_ENV% set

.github/actions/test-windows/action.yml

@@ -0,0 +1,13 @@
+name: 'Run tests on Windows'
+
+runs:
+  using: 'composite'
+  steps:
+    - name: Run CPP tests - CPU
+      shell: bash
+      env:
+        DEVICE: cpu
+      run: |
+        echo "::group::CPP tests - CPU"
+        ./build/tests/tests -tce="*gguf*,test random uniform"
+        echo "::endgroup::"

.github/workflows/build_and_test.yml

@@ -76,6 +76,18 @@ jobs:
       - uses: ./.github/actions/setup-macos
       - uses: ./.github/actions/build-macos
 
+  windows_build_and_test:
+    name: Windows (cpu, x86_64)
+    needs: check_lint
+    runs-on: windows-2025
+    steps:
+      - uses: actions/checkout@v6
+      - uses: ./.github/actions/setup-windows
+        with:
+          use-ccache: false
+      - uses: ./.github/actions/build-windows
+      - uses: ./.github/actions/test-windows
+
   build_documentation:
     name: Build Documentation
     if: github.repository == 'ml-explore/mlx'