diff --git a/.github/workflows/build-and-test-windows.yml b/.github/workflows/build-and-test-windows.yml
new file mode 100644
index 00000000..4dba58bb
--- /dev/null
+++ b/.github/workflows/build-and-test-windows.yml
@@ -0,0 +1,150 @@
+
+name: "MSYS2 Build & Test"
+
+on:
+  # allow direct trigger
+  workflow_dispatch:
+  push:
+  pull_request:
+
+concurrency:
+  group: ${{ github.workflow }}-${{ github.ref }}
+  cancel-in-progress: true
+
+permissions:
+  contents: read
+
+env:
+  COMMON_CMAKE_FLAGS: >
+    -DSLEEF_SHOW_CONFIG=1
+    -DSLEEF_BUILD_GNUABI_LIBS=ON
+    -DSLEEF_BUILD_DFT=ON
+    -DSLEEF_BUILD_QUAD=ON
+    -DSLEEF_BUILD_SCALAR_LIB=ON
+    -DSLEEF_BUILD_STATIC_TEST_BINS=ON
+    -DSLEEF_ENFORCE_TESTER=ON
+    -DSLEEF_ENFORCE_TESTER3=ON
+
+jobs:
+  build-msys2:
+    runs-on: windows-latest
+    strategy:
+      fail-fast: false
+      matrix:
+        sys:
+          - clang64
+          #- mingw64
+          #- ucrt64
+    defaults:
+      run:
+        shell: msys2 {0}
+    name: build-msys2-${{ matrix.sys }}
+    steps:
+      - name: Disable autocrlf
+        shell: pwsh
+        run: |
+          git config --global core.autocrlf false
+          git config --global core.eol lf
+
+      - uses: msys2/setup-msys2@v2
+        with:
+          msystem: ${{ matrix.sys }}
+          update: true
+          install: >-
+            git
+          pacboy: >-
+            cmake:p
+            ninja:p
+            cc:p
+            pkgconf:p
+            mpfr:p
+            openssl:p
+
+      - uses: actions/checkout@v4.1.1
+        with:
+          persist-credentials: false
+
+      - name: Build msys2
+        shell: msys2 {0}
+        run: |
+          EXTRA_CMAKE_FLAGS="-DSLEEF_ENFORCE_SSE2=ON -DSLEEF_ENFORCE_SSE4=ON -DSLEEF_ENFORCE_AVX=ON -DSLEEF_ENFORCE_AVX=ON -DSLEEF_ENFORCE_AVX2=ON -DSLEEF_ENFORCE_AVX512F=ON -DSLEEF_ENFORCE_FMA4=ON"
+          cmake -S . -B _build-msys2 -GNinja \
+            -DCMAKE_INSTALL_PREFIX=$(pwd)/_install-msys2 \
+            ${COMMON_CMAKE_FLAGS} \
+            ${EXTRA_CMAKE_FLAGS} \
+            -DOPENSSL_EXTRA_LIBRARIES="-lws2_32 -lcrypt32"
+          cmake --build _build-msys2
+          cmake --install _build-msys2
+
+      - name: Upload build-msys2-${{ matrix.sys }} artifacts
+        uses: actions/upload-artifact@v3
+        with:
+          name: build-msys2-${{ matrix.sys }}
+          path: |
+            _build-*
+            _install-*
+        if: always()
+
+  test-msys2:
+    runs-on: windows-latest
+    needs: [build-msys2]
+    strategy:
+      fail-fast: false
+      matrix:
+        sys:
+          - clang64
+          #- mingw64
+          #- ucrt64
+    defaults:
+      run:
+        shell: msys2 {0}
+    name: test-msys2-${{ matrix.sys }}
+    steps:
+      - name: Disable autocrlf
+        shell: pwsh
+        run: |
+          git config --global core.autocrlf false
+          git config --global core.eol lf
+
+      - uses: msys2/setup-msys2@v2
+        with:
+          msystem: ${{ matrix.sys }}
+          update: true
+          install: >-
+            git
+          pacboy: >-
+            cmake:p
+            ninja:p
+            cc:p
+            pkgconf:p
+            mpfr:p
+            openssl:p
+
+      - uses: actions/checkout@v4.1.1
+        with:
+          persist-credentials: false
+
+      - name: Print host CPU info
+        run: |
+          wget -qO- https://download.sysinternals.com/files/Coreinfo.zip | bsdtar -xf-
+          ./Coreinfo64.exe -accepteula
+
+      - name: Download build-msys2-${{ matrix.sys }} artifacts
+        uses: actions/download-artifact@v3
+        with:
+          name: build-msys2-${{ matrix.sys }}
+
+      - name: Test msys2
+        env:
+          CTEST_OUTPUT_ON_FAILURE: "TRUE"
+        run: |
+          cd _build-msys2
+          ctest -j$(nproc)
+
+      - name: Upload test-msys2 artifacts
+        uses: actions/upload-artifact@v3
+        with:
+          name: test-msys2
+          path: |
+            _build-msys2/Testing
+        if: always()
diff --git a/.github/workflows/build-cross-windows.yml b/.github/workflows/build-cross-windows.yml
new file mode 100644
index 00000000..ada01915
--- /dev/null
+++ b/.github/workflows/build-cross-windows.yml
@@ -0,0 +1,108 @@
+
+name: "LLVM-MinGW Cross Build"
+
+on:
+  # allow direct trigger
+  workflow_dispatch:
+  push:
+  pull_request:
+
+concurrency:
+  group: ${{ github.workflow }}-${{ github.ref }}
+  cancel-in-progress: true
+
+permissions:
+  contents: read
+
+env:
+  COMMON_CMAKE_FLAGS: >
+    -DSLEEF_BUILD_TESTS=OFF
+    -DSLEEF_SHOW_CONFIG=1
+    -DSLEEF_BUILD_GNUABI_LIBS=ON
+    -DSLEEF_BUILD_INLINE_HEADERS=ON
+    -DSLEEF_BUILD_DFT=ON
+    -DSLEEF_BUILD_QUAD=ON
+    -DSLEEF_BUILD_SCALAR_LIB=ON
+    -DSLEEF_BUILD_STATIC_TEST_BINS=ON
+
+jobs:
+  build-llvm-mingw:
+    runs-on: ubuntu-latest
+    strategy:
+      fail-fast: false
+      matrix:
+        arch: [aarch64, x86_64]
+
+    name: build-${{ matrix.arch }}
+    steps:
+      - uses: actions/checkout@v4.1.1
+        with:
+          persist-credentials: false
+
+      - name: Install dependencies
+        run: |
+          sudo apt-get update -y -qq
+          sudo apt-get install -y -qq build-essential curl ninja-build libgmp-dev libmpfr-dev debootstrap 7zip
+
+      - name: Download llvm-mingw
+        uses: robinraju/release-downloader@main
+        with:
+          repository: "mstorsjo/llvm-mingw"
+          latest: true
+          extract: false
+          fileName: "llvm-mingw-*-ucrt-ubuntu-*-x86_64.tar.xz"
+
+      - name: Install llvm-mingw
+        run: |
+          tar -xaf llvm-mingw-*.tar.xz && rm llvm-mingw-*.tar.xz
+          mv llvm-mingw-* llvm-mingw
+          echo ORIGIN_PATH="$PATH" >> $GITHUB_ENV
+          echo PATH="$PWD/llvm-mingw/bin:$PATH" >> $GITHUB_ENV
+
+      - name: Build native
+        shell: bash -ex -o pipefail {0}
+        run: |
+          EXTRA_CMAKE_FLAGS="-DSLEEF_ENFORCE_SSE2=ON -DSLEEF_ENFORCE_SSE4=ON -DSLEEF_ENFORCE_AVX=ON -DSLEEF_ENFORCE_AVX=ON -DSLEEF_ENFORCE_AVX2=ON -DSLEEF_ENFORCE_AVX512F=ON -DSLEEF_ENFORCE_FMA4=ON"
+          PATH=$ORIGIN_PATH
+          cmake -S . -B _build-native -GNinja \
+            -DCMAKE_INSTALL_PREFIX=$(pwd)/_install-native \
+            -DCMAKE_TOOLCHAIN_FILE=$(pwd)/toolchains/native-llvm.cmake \
+            ${COMMON_CMAKE_FLAGS} \
+            ${EXTRA_CMAKE_FLAGS}
+          cmake --build _build-native
+          cmake --install _build-native
+
+      - name: Fix _build-native permissions
+        run: |
+          chmod +x _build-native/bin/*
+
+      - name: Build llvm-mingw-${{ matrix.arch }}
+        shell: bash -ex -o pipefail {0}
+        run: |
+          EXTRA_CMAKE_FLAGS=""
+          if [[ ${{ matrix.arch }} = "aarch64" ]]; then
+            EXTRA_CMAKE_FLAGS="${EXTRA_CMAKE_FLAGS}"
+          elif [[ ${{ matrix.arch }} = "x86_64" ]]; then
+            EXTRA_CMAKE_FLAGS="${EXTRA_CMAKE_FLAGS} -DSLEEF_ENFORCE_SSE2=ON -DSLEEF_ENFORCE_SSE4=ON -DSLEEF_ENFORCE_AVX=ON -DSLEEF_ENFORCE_AVX=ON -DSLEEF_ENFORCE_AVX2=ON -DSLEEF_ENFORCE_AVX512F=ON -DSLEEF_ENFORCE_FMA4=ON"
+          fi
+
+          cmake -S . -B _build-${{ matrix.arch }} -GNinja \
+            -DCMAKE_INSTALL_PREFIX="$(pwd)/_install-${{ matrix.arch }}" \
+            -DCMAKE_SYSROOT="$(pwd)/llvm-mingw/${{ matrix.arch }}-w64-mingw32" \
+            -DNATIVE_BUILD_DIR="$(pwd)/_build-native" \
+            ${COMMON_CMAKE_FLAGS} \
+            -DCMAKE_C_COMPILER=${{ matrix.arch }}-w64-mingw32-clang \
+            -DCMAKE_SYSTEM_NAME=Windows \
+            -DCMAKE_SYSTEM_PROCESSOR=${{ matrix.arch }} \
+            ${EXTRA_CMAKE_FLAGS}
+          cmake --build _build-${{ matrix.arch }}
+          cmake --install _build-${{ matrix.arch }}
+
+      - name: Upload build-${{ matrix.arch }}-llvm-mingw artifacts
+        uses: actions/upload-artifact@v3
+        with:
+          name: build-${{ matrix.arch }}-llvm-mingw
+          path: |
+            _build-${{ matrix.arch }}
+            _install-${{ matrix.arch }}
+        if: always()