diff --git a/.github/workflows/main.yaml b/.github/workflows/main.yaml
index d13dd6b0..1ec64037 100644
--- a/.github/workflows/main.yaml
+++ b/.github/workflows/main.yaml
@@ -44,54 +44,54 @@ jobs:
       fail-fast: false
       matrix:
         include:
-        - target: aarch64-apple-darwin
-          os: macos-15
-        - target: aarch64-unknown-linux-gnu
-          os: ubuntu-24.04-arm
-        - target: aarch64-pc-windows-msvc
-          os: windows-2025
-          test_verbatim: 1
-          build_only: 1
-        - target: arm-unknown-linux-gnueabi
-          os: ubuntu-24.04
-        - target: arm-unknown-linux-gnueabihf
-          os: ubuntu-24.04
-        - target: armv7-unknown-linux-gnueabihf
-          os: ubuntu-24.04
-        - target: i586-unknown-linux-gnu
-          os: ubuntu-24.04
-        - target: i686-unknown-linux-gnu
-          os: ubuntu-24.04
-        - target: loongarch64-unknown-linux-gnu
-          os: ubuntu-24.04
-        - target: powerpc-unknown-linux-gnu
-          os: ubuntu-24.04
-        - target: powerpc64-unknown-linux-gnu
-          os: ubuntu-24.04
-        - target: powerpc64le-unknown-linux-gnu
-          os: ubuntu-24.04
-        - target: riscv64gc-unknown-linux-gnu
-          os: ubuntu-24.04
-        - target: thumbv6m-none-eabi
-          os: ubuntu-24.04
-        - target: thumbv7em-none-eabi
-          os: ubuntu-24.04
-        - target: thumbv7em-none-eabihf
-          os: ubuntu-24.04
-        - target: thumbv7m-none-eabi
-          os: ubuntu-24.04
-        - target: wasm32-unknown-unknown
-          os: ubuntu-24.04
-        - target: x86_64-unknown-linux-gnu
-          os: ubuntu-24.04
-        - target: x86_64-apple-darwin
-          os: macos-13
-        - target: i686-pc-windows-msvc
-          os: windows-2025
-          test_verbatim: 1
-        - target: x86_64-pc-windows-msvc
-          os: windows-2025
-          test_verbatim: 1
+        # - target: aarch64-apple-darwin
+        #   os: macos-15
+        # - target: aarch64-unknown-linux-gnu
+        #   os: ubuntu-24.04-arm
+        # - target: aarch64-pc-windows-msvc
+        #   os: windows-2025
+        #   test_verbatim: 1
+        #   build_only: 1
+        # - target: arm-unknown-linux-gnueabi
+        #   os: ubuntu-24.04
+        # - target: arm-unknown-linux-gnueabihf
+        #   os: ubuntu-24.04
+        # - target: armv7-unknown-linux-gnueabihf
+        #   os: ubuntu-24.04
+        # - target: i586-unknown-linux-gnu
+        #   os: ubuntu-24.04
+        # - target: i686-unknown-linux-gnu
+        #   os: ubuntu-24.04
+        # - target: loongarch64-unknown-linux-gnu
+        #   os: ubuntu-24.04
+        # - target: powerpc-unknown-linux-gnu
+        #   os: ubuntu-24.04
+        # - target: powerpc64-unknown-linux-gnu
+        #   os: ubuntu-24.04
+        # - target: powerpc64le-unknown-linux-gnu
+        #   os: ubuntu-24.04
+        # - target: riscv64gc-unknown-linux-gnu
+        #   os: ubuntu-24.04
+        # - target: thumbv6m-none-eabi
+        #   os: ubuntu-24.04
+        # - target: thumbv7em-none-eabi
+        #   os: ubuntu-24.04
+        # - target: thumbv7em-none-eabihf
+        #   os: ubuntu-24.04
+        # - target: thumbv7m-none-eabi
+        #   os: ubuntu-24.04
+        # - target: wasm32-unknown-unknown
+        #   os: ubuntu-24.04
+        # - target: x86_64-unknown-linux-gnu
+        #   os: ubuntu-24.04
+        # - target: x86_64-apple-darwin
+        #   os: macos-13
+        # - target: i686-pc-windows-msvc
+        #   os: windows-2025
+        #   test_verbatim: 1
+        # - target: x86_64-pc-windows-msvc
+        #   os: windows-2025
+        #   test_verbatim: 1
         - target: i686-pc-windows-gnu
           os: windows-2025
           channel: nightly-i686-gnu
@@ -110,72 +110,96 @@ jobs:
     - uses: actions/checkout@v4
       with:
         submodules: true
-    - name: Install Rust (rustup)
-      shell: bash
-      run: |
-        channel="nightly"
-        # Account for channels that have required components (MinGW)
-        [ -n "${{ matrix.channel }}" ] && channel="${{ matrix.channel }}"
-        rustup update "$channel" --no-self-update
-        rustup default "$channel"
-        rustup target add "${{ matrix.target }}"
-        rustup component add llvm-tools-preview
-    - uses: taiki-e/install-action@nextest
-    - uses: Swatinem/rust-cache@v2
-      with:
-        key: ${{ matrix.target }}
-    - name: Cache Docker layers
-      uses: actions/cache@v4
-      if: matrix.os == 'ubuntu-24.04'
-      with:
-        path: /tmp/.buildx-cache
-        key: ${{ matrix.target }}-buildx-${{ github.sha }}
-        restore-keys: ${{ matrix.target }}-buildx-
-    # Configure buildx to use Docker layer caching
-    - uses: docker/setup-buildx-action@v3
-      if: matrix.os == 'ubuntu-24.04'
+    # - name: Install Rust (rustup)
+    #   shell: bash
+    #   run: |
+    #     channel="nightly"
+    #     # Account for channels that have required components (MinGW)
+    #     [ -n "${{ matrix.channel }}" ] && channel="${{ matrix.channel }}"
+    #     rustup update "$channel" --no-self-update
+    #     rustup default "$channel"
+    #     rustup target add "${{ matrix.target }}"
+    #     rustup component add llvm-tools-preview
+    # - uses: taiki-e/install-action@nextest
+    # - uses: Swatinem/rust-cache@v2
+    #   with:
+    #     key: ${{ matrix.target }}
+    # - name: Cache Docker layers
+    #   uses: actions/cache@v4
+    #   if: matrix.os == 'ubuntu-24.04'
+    #   with:
+    #     path: /tmp/.buildx-cache
+    #     key: ${{ matrix.target }}-buildx-${{ github.sha }}
+    #     restore-keys: ${{ matrix.target }}-buildx-
+    # # Configure buildx to use Docker layer caching
+    # - uses: docker/setup-buildx-action@v3
+    #   if: matrix.os == 'ubuntu-24.04'
 
-    - name: Cache compiler-rt
-      id: cache-compiler-rt
-      uses: actions/cache@v4
+    # - name: Cache compiler-rt
+    #   id: cache-compiler-rt
+    #   uses: actions/cache@v4
+    #   with:
+    #     path: compiler-rt
+    #     key: ${{ runner.os }}-compiler-rt-${{ hashFiles('ci/download-compiler-rt.sh') }}
+    # - name: Download compiler-rt reference sources
+    #   if: steps.cache-compiler-rt.outputs.cache-hit != 'true'
+    #   run: ./ci/download-compiler-rt.sh
+    #   shell: bash
+    # - run: echo "RUST_COMPILER_RT_ROOT=$(realpath ./compiler-rt)" >> "$GITHUB_ENV"
+    #   shell: bash
+
+    # - name: Verify API list
+    #   if: matrix.os == 'ubuntu-24.04'
+    #   run: python3 etc/update-api-list.py --check
+
+    - uses: msys2/setup-msys2@v2
+      if: matrix.os == 'windows-2025'
       with:
-        path: compiler-rt
-        key: ${{ runner.os }}-compiler-rt-${{ hashFiles('ci/download-compiler-rt.sh') }}
-    - name: Download compiler-rt reference sources
-      if: steps.cache-compiler-rt.outputs.cache-hit != 'true'
-      run: ./ci/download-compiler-rt.sh
-      shell: bash
-    - run: echo "RUST_COMPILER_RT_ROOT=$(realpath ./compiler-rt)" >> "$GITHUB_ENV"
-      shell: bash
+        msystem: UCRT64
+        update: true
+        install: diffutils m4 make # mingw-w64-rustup
 
-    - name: Verify API list
-      if: matrix.os == 'ubuntu-24.04'
-      run: python3 etc/update-api-list.py --check
+    - name: Setup windows
+      if: matrix.os == 'windows-2025'
+      shell: msys2 {0}
+      run: |
+        ./ci/run-windows.sh ${{ matrix.target }}
 
-    # Non-linux tests just use our raw script
-    - name: Run locally
-      if: matrix.os != 'ubuntu-24.04'
-      shell: bash
-      run: ./ci/run.sh ${{ matrix.target }}
+    - name: Run on Windows
+      if: matrix.os == 'windows-2025'
+      shell: msys2 {0}
+      run: |
+        rustc -vV
+        rustup show
+        ./ci/run.sh ${{ matrix.target }}
 
-    # Otherwise we use our docker containers to run builds
-    - name: Run in Docker
-      if: matrix.os == 'ubuntu-24.04'
-      run: ./ci/run-docker.sh ${{ matrix.target }}
+    # # Non-linux tests just use our raw script
+    # - name: Run locally
+    #   if: matrix.os != 'ubuntu-24.04'
+    #   shell: bash
+    #   run: ./ci/run.sh ${{ matrix.target }}
+
+    # # Otherwise we use our docker containers to run builds
+    # - name: Run in Docker
+    #   if: matrix.os == 'ubuntu-24.04'
+    #   run: ./ci/run-docker.sh ${{ matrix.target }}
 
     - name: Print test logs if available
       if: always()
-      run: if [ -f "target/test-log.txt" ]; then cat target/test-log.txt; fi
+      run: |
+        if [ -f "target/test-log.txt" ]; then cat target/test-log.txt; fi
+        set -x
+        find . -name 'config.log' -exec cat {} ';'
       shell: bash
 
-    # Workaround to keep Docker cache smaller
-    # https://github.com/docker/build-push-action/issues/252
-    # https://github.com/moby/buildkit/issues/1896
-    - name: Move Docker cache
-      if: matrix.os == 'ubuntu-24.04'
-      run: |
-        rm -rf /tmp/.buildx-cache
-        mv /tmp/.buildx-cache-new /tmp/.buildx-cache
+    # # Workaround to keep Docker cache smaller
+    # # https://github.com/docker/build-push-action/issues/252
+    # # https://github.com/moby/buildkit/issues/1896
+    # - name: Move Docker cache
+    #   if: matrix.os == 'ubuntu-24.04'
+    #   run: |
+    #     rm -rf /tmp/.buildx-cache
+    #     mv /tmp/.buildx-cache-new /tmp/.buildx-cache
 
   clippy:
     name: Clippy
@@ -194,143 +218,143 @@ jobs:
     - uses: Swatinem/rust-cache@v2
     - run: cargo clippy --workspace --all-targets
 
-  benchmarks:
-    name: Benchmarks
-    runs-on: ubuntu-24.04
-    timeout-minutes: 20
-    steps:
-    - uses: actions/checkout@master
-      with:
-        submodules: true
-    - uses: taiki-e/install-action@cargo-binstall
+  # benchmarks:
+  #   name: Benchmarks
+  #   runs-on: ubuntu-24.04
+  #   timeout-minutes: 20
+  #   steps:
+  #   - uses: actions/checkout@master
+  #     with:
+  #       submodules: true
+  #   - uses: taiki-e/install-action@cargo-binstall
 
-    - name: Set up dependencies
-      run: |
-        sudo apt-get update
-        sudo apt-get install -y valgrind gdb libc6-dbg # Needed for iai-callgrind
-        rustup update "$BENCHMARK_RUSTC" --no-self-update
-        rustup default "$BENCHMARK_RUSTC"
-        # Install the version of iai-callgrind-runner that is specified in Cargo.toml
-        iai_version="$(cargo metadata --format-version=1 --features icount |
-           jq -r '.packages[] | select(.name == "iai-callgrind").version')"
-        cargo binstall -y iai-callgrind-runner --version "$iai_version"
-        sudo apt-get install valgrind
-    - uses: Swatinem/rust-cache@v2
+  #   - name: Set up dependencies
+  #     run: |
+  #       sudo apt-get update
+  #       sudo apt-get install -y valgrind gdb libc6-dbg # Needed for iai-callgrind
+  #       rustup update "$BENCHMARK_RUSTC" --no-self-update
+  #       rustup default "$BENCHMARK_RUSTC"
+  #       # Install the version of iai-callgrind-runner that is specified in Cargo.toml
+  #       iai_version="$(cargo metadata --format-version=1 --features icount |
+  #          jq -r '.packages[] | select(.name == "iai-callgrind").version')"
+  #       cargo binstall -y iai-callgrind-runner --version "$iai_version"
+  #       sudo apt-get install valgrind
+  #   - uses: Swatinem/rust-cache@v2
 
-    - name: Run icount benchmarks
-      env:
-        GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
-        PR_NUMBER: ${{ github.event.pull_request.number }}
-      run: ./ci/bench-icount.sh
+  #   - name: Run icount benchmarks
+  #     env:
+  #       GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
+  #       PR_NUMBER: ${{ github.event.pull_request.number }}
+  #     run: ./ci/bench-icount.sh
 
-    - name: Upload the benchmark baseline
-      uses: actions/upload-artifact@v4
-      with:
-        name: ${{ env.BASELINE_NAME }}
-        path: ${{ env.BASELINE_NAME }}.tar.xz
+  #   - name: Upload the benchmark baseline
+  #     uses: actions/upload-artifact@v4
+  #     with:
+  #       name: ${{ env.BASELINE_NAME }}
+  #       path: ${{ env.BASELINE_NAME }}.tar.xz
     
-    - name: Run wall time benchmarks
-      run: |
-        # Always use the same seed for benchmarks. Ideally we should switch to a
-        # non-random generator.
-        export LIBM_SEED=benchesbenchesbenchesbencheswoo!
-        cargo bench --package libm-test \
-          --no-default-features \
-          --features short-benchmarks,build-musl,libm/force-soft-floats
+  #   - name: Run wall time benchmarks
+  #     run: |
+  #       # Always use the same seed for benchmarks. Ideally we should switch to a
+  #       # non-random generator.
+  #       export LIBM_SEED=benchesbenchesbenchesbencheswoo!
+  #       cargo bench --package libm-test \
+  #         --no-default-features \
+  #         --features short-benchmarks,build-musl,libm/force-soft-floats
 
-    - name: Print test logs if available
-      if: always()
-      run: if [ -f "target/test-log.txt" ]; then cat target/test-log.txt; fi
-      shell: bash
+  #   - name: Print test logs if available
+  #     if: always()
+  #     run: if [ -f "target/test-log.txt" ]; then cat target/test-log.txt; fi
+  #     shell: bash
 
-  miri:
-    name: Miri
-    runs-on: ubuntu-24.04
-    timeout-minutes: 10
-    steps:
-    - uses: actions/checkout@v4
-      with:
-        submodules: true
-    - name: Install Rust (rustup)
-      run: rustup update nightly --no-self-update && rustup default nightly
-      shell: bash
-    - run: rustup component add miri
-    - run: cargo miri setup
-    - uses: Swatinem/rust-cache@v2
-    - run: ./ci/miri.sh
+  # miri:
+  #   name: Miri
+  #   runs-on: ubuntu-24.04
+  #   timeout-minutes: 10
+  #   steps:
+  #   - uses: actions/checkout@v4
+  #     with:
+  #       submodules: true
+  #   - name: Install Rust (rustup)
+  #     run: rustup update nightly --no-self-update && rustup default nightly
+  #     shell: bash
+  #   - run: rustup component add miri
+  #   - run: cargo miri setup
+  #   - uses: Swatinem/rust-cache@v2
+  #   - run: ./ci/miri.sh
 
-  msrv:
-    name: Check libm MSRV
-    runs-on: ubuntu-24.04
-    timeout-minutes: 10
-    env:
-      RUSTFLAGS: # No need to check warnings on old MSRV, unset `-Dwarnings`
-    steps:
-    - uses: actions/checkout@master
-    - name: Install Rust
-      run: |
-        msrv="$(perl -ne 'print if s/rust-version\s*=\s*"(.*)"/\1/g' libm/Cargo.toml)"
-        echo "MSRV: $msrv"
-        rustup update "$msrv" --no-self-update && rustup default "$msrv"
-    - uses: Swatinem/rust-cache@v2
-    - run: |
-        # FIXME(msrv): Remove the workspace Cargo.toml so 1.63 cargo doesn't see
-        # `edition = "2024"` and get spooked.
-        rm Cargo.toml
-        cargo build --manifest-path libm/Cargo.toml
+  # msrv:
+  #   name: Check libm MSRV
+  #   runs-on: ubuntu-24.04
+  #   timeout-minutes: 10
+  #   env:
+  #     RUSTFLAGS: # No need to check warnings on old MSRV, unset `-Dwarnings`
+  #   steps:
+  #   - uses: actions/checkout@master
+  #   - name: Install Rust
+  #     run: |
+  #       msrv="$(perl -ne 'print if s/rust-version\s*=\s*"(.*)"/\1/g' libm/Cargo.toml)"
+  #       echo "MSRV: $msrv"
+  #       rustup update "$msrv" --no-self-update && rustup default "$msrv"
+  #   - uses: Swatinem/rust-cache@v2
+  #   - run: |
+  #       # FIXME(msrv): Remove the workspace Cargo.toml so 1.63 cargo doesn't see
+  #       # `edition = "2024"` and get spooked.
+  #       rm Cargo.toml
+  #       cargo build --manifest-path libm/Cargo.toml
 
-  rustfmt:
-    name: Rustfmt
-    runs-on: ubuntu-24.04
-    timeout-minutes: 10
-    steps:
-    - uses: actions/checkout@v4
-      with:
-        submodules: true
-    - name: Install stable `rustfmt`
-      run: rustup set profile minimal && rustup default stable && rustup component add rustfmt
-    - run: cargo fmt -- --check
+  # rustfmt:
+  #   name: Rustfmt
+  #   runs-on: ubuntu-24.04
+  #   timeout-minutes: 10
+  #   steps:
+  #   - uses: actions/checkout@v4
+  #     with:
+  #       submodules: true
+  #   - name: Install stable `rustfmt`
+  #     run: rustup set profile minimal && rustup default stable && rustup component add rustfmt
+  #   - run: cargo fmt -- --check
 
-  extensive:
-    name: Extensive tests for ${{ matrix.ty }}
-    needs:
-      # Wait on `clippy` so we have some confidence that the crate will build
-      - clippy
-      - calculate_vars
-    runs-on: ubuntu-24.04
-    timeout-minutes: 240 # 4 hours
-    strategy:
-      matrix:
-        # Use the output from `calculate_vars` to create the matrix
-        # FIXME: it would be better to run all jobs (i.e. all types) but mark those that
-        # didn't change as skipped, rather than completely excluding the job. However,
-        # this is not currently possible https://github.com/actions/runner/issues/1985.
-        include: ${{ fromJSON(needs.calculate_vars.outputs.extensive_matrix).extensive_matrix }}
-    env:
-      TO_TEST: ${{ matrix.to_test }}
-    steps:
-      - uses: actions/checkout@v4
-        with:
-          submodules: true
-      - name: Install Rust
-        run: |
-          rustup update nightly --no-self-update
-          rustup default nightly
-      - uses: Swatinem/rust-cache@v2
-      - name: Run extensive tests
-        run: ./ci/run-extensive.sh
-      - name: Print test logs if available
-        run: if [ -f "target/test-log.txt" ]; then cat target/test-log.txt; fi
-        shell: bash
+  # extensive:
+  #   name: Extensive tests for ${{ matrix.ty }}
+  #   needs:
+  #     # Wait on `clippy` so we have some confidence that the crate will build
+  #     - clippy
+  #     - calculate_vars
+  #   runs-on: ubuntu-24.04
+  #   timeout-minutes: 240 # 4 hours
+  #   strategy:
+  #     matrix:
+  #       # Use the output from `calculate_vars` to create the matrix
+  #       # FIXME: it would be better to run all jobs (i.e. all types) but mark those that
+  #       # didn't change as skipped, rather than completely excluding the job. However,
+  #       # this is not currently possible https://github.com/actions/runner/issues/1985.
+  #       include: ${{ fromJSON(needs.calculate_vars.outputs.extensive_matrix).extensive_matrix }}
+  #   env:
+  #     TO_TEST: ${{ matrix.to_test }}
+  #   steps:
+  #     - uses: actions/checkout@v4
+  #       with:
+  #         submodules: true
+  #     - name: Install Rust
+  #       run: |
+  #         rustup update nightly --no-self-update
+  #         rustup default nightly
+  #     - uses: Swatinem/rust-cache@v2
+  #     - name: Run extensive tests
+  #       run: ./ci/run-extensive.sh
+  #     - name: Print test logs if available
+  #       run: if [ -f "target/test-log.txt" ]; then cat target/test-log.txt; fi
+  #       shell: bash
 
   success:
     needs:
-      - benchmarks
+      # - benchmarks
       - clippy
-      - extensive
-      - miri
-      - msrv
-      - rustfmt
+      # - extensive
+      # - miri
+      # - msrv
+      # - rustfmt
       - test
     runs-on: ubuntu-24.04
     timeout-minutes: 10
diff --git a/ci/run-windows.sh b/ci/run-windows.sh
new file mode 100755
index 00000000..cc8e076d
--- /dev/null
+++ b/ci/run-windows.sh
@@ -0,0 +1,29 @@
+#!/bin/bash
+
+set -eux
+
+target="$1"
+
+m4 --help
+make --help
+
+echo "$PATH"
+
+curl --proto '=https' --tlsv1.2 -sSf https://sh.rustup.rs | sh -s -- \
+    --default-toolchain nightly-x86_64-gnu \
+    --target "$target" \
+    --profile minimal -y
+
+# Wrapper to ease managerment of environments
+pacman --noconfirm -S pactoys
+# Install C toolchain according to `MSYSTEM`
+pacboy --noconfirm -S toolchain
+
+pacman --noconfirm -S mingw-w64-x86_64-toolchain
+
+# maybe only need mingw-w64-x86_64-gcc?
+
+ls ~/
+echo 'export PATH="/c/Users/$USERNAME/.cargo/bin:$PATH"' >> ~/.bash_profile
+
+echo "$PATH"
diff --git a/ci/run.sh b/ci/run.sh
index 68d13c13..683fe4cb 100755
--- a/ci/run.sh
+++ b/ci/run.sh
@@ -2,6 +2,10 @@
 
 set -eux
 
+echo PATH_DBG
+echo $PATH
+ls /c/Users/$USERNAME/.cargo/bin
+
 export RUST_BACKTRACE="${RUST_BACKTRACE:-full}"
 export NEXTEST_STATUS_LEVEL=all
 
@@ -25,152 +29,152 @@ if [ "${USING_CONTAINER_RUSTC:-}" = 1 ]; then
         rustup target add "$target"
 fi
 
-# Test our implementation
-if [ "${BUILD_ONLY:-}" = "1" ]; then
-    echo "no tests to run for build-only targets"
-else
-    test_builtins=(cargo test --package builtins-test --no-fail-fast --target "$target")
-    "${test_builtins[@]}"
-    "${test_builtins[@]}" --release
-    "${test_builtins[@]}" --features c
-    "${test_builtins[@]}" --features c --release
-    "${test_builtins[@]}" --features no-asm
-    "${test_builtins[@]}" --features no-asm --release
-    "${test_builtins[@]}" --features no-f16-f128
-    "${test_builtins[@]}" --features no-f16-f128 --release
-    "${test_builtins[@]}" --benches
-    "${test_builtins[@]}" --benches --release
-
-    if [ "${TEST_VERBATIM:-}" = "1" ]; then
-        verb_path=$(cmd.exe //C echo \\\\?\\%cd%\\builtins-test\\target2)
-        "${test_builtins[@]}" --target-dir "$verb_path" --features c
-    fi
-fi
-
-
-declare -a rlib_paths
-
-# Set the `rlib_paths` global array to a list of all compiler-builtins rlibs
-update_rlib_paths() {
-    if [ -d /builtins-target ]; then
-        rlib_paths=( /builtins-target/"${target}"/debug/deps/libcompiler_builtins-*.rlib )
-    else
-        rlib_paths=( target/"${target}"/debug/deps/libcompiler_builtins-*.rlib )
-    fi
-}
-
-# Remove any existing artifacts from previous tests that don't set #![compiler_builtins]
-update_rlib_paths
-rm -f "${rlib_paths[@]}"
-
-cargo build -p compiler_builtins --target "$target"
-cargo build -p compiler_builtins --target "$target" --release
-cargo build -p compiler_builtins --target "$target" --features c
-cargo build -p compiler_builtins --target "$target" --features c --release
-cargo build -p compiler_builtins --target "$target" --features no-asm
-cargo build -p compiler_builtins --target "$target" --features no-asm --release
-cargo build -p compiler_builtins --target "$target" --features no-f16-f128
-cargo build -p compiler_builtins --target "$target" --features no-f16-f128 --release
-
-PREFIX=${target//unknown-/}-
-case "$target" in
-    armv7-*)
-        PREFIX=arm-linux-gnueabihf-
-        ;;
-    thumb*)
-        PREFIX=arm-none-eabi-
-        ;;
-    *86*-*)
-        PREFIX=
-        ;;
-esac
-
-NM=$(find "$(rustc --print sysroot)" \( -name llvm-nm -o -name llvm-nm.exe \) )
-if [ "$NM" = "" ]; then
-  NM="${PREFIX}nm"
-fi
-
-# i686-pc-windows-gnu tools have a dependency on some DLLs, so run it with
-# rustup run to ensure that those are in PATH.
-TOOLCHAIN="$(rustup show active-toolchain | sed 's/ (default)//')"
-if [[ "$TOOLCHAIN" == *i686-pc-windows-gnu ]]; then
-  NM="rustup run $TOOLCHAIN $NM"
-fi
-
-# Look out for duplicated symbols when we include the compiler-rt (C) implementation
-update_rlib_paths
-for rlib in "${rlib_paths[@]}"; do
-    set +x
-    echo "================================================================"
-    echo "checking $rlib for duplicate symbols"
-    echo "================================================================"
-    set -x
+# # Test our implementation
+# if [ "${BUILD_ONLY:-}" = "1" ]; then
+#     echo "no tests to run for build-only targets"
+# else
+#     test_builtins=(cargo test --package builtins-test --no-fail-fast --target "$target")
+#     "${test_builtins[@]}"
+#     "${test_builtins[@]}" --release
+#     "${test_builtins[@]}" --features c
+#     "${test_builtins[@]}" --features c --release
+#     "${test_builtins[@]}" --features no-asm
+#     "${test_builtins[@]}" --features no-asm --release
+#     "${test_builtins[@]}" --features no-f16-f128
+#     "${test_builtins[@]}" --features no-f16-f128 --release
+#     "${test_builtins[@]}" --benches
+#     "${test_builtins[@]}" --benches --release
+
+#     if [ "${TEST_VERBATIM:-}" = "1" ]; then
+#         verb_path=$(cmd.exe //C echo \\\\?\\%cd%\\builtins-test\\target2)
+#         "${test_builtins[@]}" --target-dir "$verb_path" --features c
+#     fi
+# fi
+
+
+# declare -a rlib_paths
+
+# # Set the `rlib_paths` global array to a list of all compiler-builtins rlibs
+# update_rlib_paths() {
+#     if [ -d /builtins-target ]; then
+#         rlib_paths=( /builtins-target/"${target}"/debug/deps/libcompiler_builtins-*.rlib )
+#     else
+#         rlib_paths=( target/"${target}"/debug/deps/libcompiler_builtins-*.rlib )
+#     fi
+# }
+
+# # Remove any existing artifacts from previous tests that don't set #![compiler_builtins]
+# update_rlib_paths
+# rm -f "${rlib_paths[@]}"
+
+# cargo build -p compiler_builtins --target "$target"
+# cargo build -p compiler_builtins --target "$target" --release
+# cargo build -p compiler_builtins --target "$target" --features c
+# cargo build -p compiler_builtins --target "$target" --features c --release
+# cargo build -p compiler_builtins --target "$target" --features no-asm
+# cargo build -p compiler_builtins --target "$target" --features no-asm --release
+# cargo build -p compiler_builtins --target "$target" --features no-f16-f128
+# cargo build -p compiler_builtins --target "$target" --features no-f16-f128 --release
+
+# PREFIX=${target//unknown-/}-
+# case "$target" in
+#     armv7-*)
+#         PREFIX=arm-linux-gnueabihf-
+#         ;;
+#     thumb*)
+#         PREFIX=arm-none-eabi-
+#         ;;
+#     *86*-*)
+#         PREFIX=
+#         ;;
+# esac
+
+# NM=$(find "$(rustc --print sysroot)" \( -name llvm-nm -o -name llvm-nm.exe \) )
+# if [ "$NM" = "" ]; then
+#   NM="${PREFIX}nm"
+# fi
+
+# # i686-pc-windows-gnu tools have a dependency on some DLLs, so run it with
+# # rustup run to ensure that those are in PATH.
+# TOOLCHAIN="$(rustup show active-toolchain | sed 's/ (default)//')"
+# if [[ "$TOOLCHAIN" == *i686-pc-windows-gnu ]]; then
+#   NM="rustup run $TOOLCHAIN $NM"
+# fi
+
+# # Look out for duplicated symbols when we include the compiler-rt (C) implementation
+# update_rlib_paths
+# for rlib in "${rlib_paths[@]}"; do
+#     set +x
+#     echo "================================================================"
+#     echo "checking $rlib for duplicate symbols"
+#     echo "================================================================"
+#     set -x
     
-    duplicates_found=0
-
-    # NOTE On i586, It's normal that the get_pc_thunk symbol appears several
-    # times so ignore it
-    $NM -g --defined-only "$rlib" 2>&1 |
-      sort |
-      uniq -d |
-      grep -v __x86.get_pc_thunk --quiet |
-      grep 'T __' && duplicates_found=1
-
-    if [ "$duplicates_found" != 0 ]; then
-        echo "error: found duplicate symbols"
-        exit 1
-    else
-        echo "success; no duplicate symbols found"
-    fi
-done
-
-rm -f "${rlib_paths[@]}"
-
-build_intrinsics_test() {
-    cargo build \
-        --target "$target" --verbose \
-        --manifest-path builtins-test-intrinsics/Cargo.toml "$@"
-}
-
-# Verify that we haven't dropped any intrinsics/symbols
-build_intrinsics_test
-build_intrinsics_test --release
-build_intrinsics_test --features c
-build_intrinsics_test --features c --release
-
-# Verify that there are no undefined symbols to `panic` within our
-# implementations
-CARGO_PROFILE_DEV_LTO=true build_intrinsics_test
-CARGO_PROFILE_RELEASE_LTO=true build_intrinsics_test --release
-
-# Ensure no references to any symbols from core
-update_rlib_paths
-for rlib in "${rlib_paths[@]}"; do
-    set +x
-    echo "================================================================"
-    echo "checking $rlib for references to core"
-    echo "================================================================"
-    set -x
-
-    tmpdir="${CARGO_TARGET_DIR:-target}/tmp"
-    test -d "$tmpdir" || mkdir "$tmpdir"
-    defined="$tmpdir/defined_symbols.txt"
-    undefined="$tmpdir/defined_symbols.txt"
-
-    $NM --quiet -U "$rlib" | grep 'T _ZN4core' | awk '{print $3}' | sort | uniq > "$defined"
-    $NM --quiet -u "$rlib" | grep 'U _ZN4core' | awk '{print $2}' | sort | uniq > "$undefined"
-    grep_has_results=0
-    grep -v -F -x -f "$defined" "$undefined" && grep_has_results=1
-
-    if [ "$target" = "powerpc64-unknown-linux-gnu" ]; then
-        echo "FIXME: powerpc64 fails these tests"
-    elif [ "$grep_has_results" != 0 ]; then
-        echo "error: found unexpected references to core"
-        exit 1
-    else
-        echo "success; no references to core found"
-    fi
-done
+#     duplicates_found=0
+
+#     # NOTE On i586, It's normal that the get_pc_thunk symbol appears several
+#     # times so ignore it
+#     $NM -g --defined-only "$rlib" 2>&1 |
+#       sort |
+#       uniq -d |
+#       grep -v __x86.get_pc_thunk --quiet |
+#       grep 'T __' && duplicates_found=1
+
+#     if [ "$duplicates_found" != 0 ]; then
+#         echo "error: found duplicate symbols"
+#         exit 1
+#     else
+#         echo "success; no duplicate symbols found"
+#     fi
+# done
+
+# rm -f "${rlib_paths[@]}"
+
+# build_intrinsics_test() {
+#     cargo build \
+#         --target "$target" --verbose \
+#         --manifest-path builtins-test-intrinsics/Cargo.toml "$@"
+# }
+
+# # Verify that we haven't dropped any intrinsics/symbols
+# build_intrinsics_test
+# build_intrinsics_test --release
+# build_intrinsics_test --features c
+# build_intrinsics_test --features c --release
+
+# # Verify that there are no undefined symbols to `panic` within our
+# # implementations
+# CARGO_PROFILE_DEV_LTO=true build_intrinsics_test
+# CARGO_PROFILE_RELEASE_LTO=true build_intrinsics_test --release
+
+# # Ensure no references to any symbols from core
+# update_rlib_paths
+# for rlib in "${rlib_paths[@]}"; do
+#     set +x
+#     echo "================================================================"
+#     echo "checking $rlib for references to core"
+#     echo "================================================================"
+#     set -x
+
+#     tmpdir="${CARGO_TARGET_DIR:-target}/tmp"
+#     test -d "$tmpdir" || mkdir "$tmpdir"
+#     defined="$tmpdir/defined_symbols.txt"
+#     undefined="$tmpdir/defined_symbols.txt"
+
+#     $NM --quiet -U "$rlib" | grep 'T _ZN4core' | awk '{print $3}' | sort | uniq > "$defined"
+#     $NM --quiet -u "$rlib" | grep 'U _ZN4core' | awk '{print $2}' | sort | uniq > "$undefined"
+#     grep_has_results=0
+#     grep -v -F -x -f "$defined" "$undefined" && grep_has_results=1
+
+#     if [ "$target" = "powerpc64-unknown-linux-gnu" ]; then
+#         echo "FIXME: powerpc64 fails these tests"
+#     elif [ "$grep_has_results" != 0 ]; then
+#         echo "error: found unexpected references to core"
+#         exit 1
+#     else
+#         echo "success; no references to core found"
+#     fi
+# done
 
 # Test libm
 
@@ -218,9 +222,9 @@ esac
 case "$target" in
     # MSVC cannot link MPFR
     *windows-msvc*) ;;
-    # FIXME: MinGW should be able to build MPFR, but setup in CI is nontrivial.
-    *windows-gnu*) ;;
     # Targets that aren't cross compiled in CI work fine
+    i686-pc-windows-gnu) mflags+=(--features libm-test/build-mpfr --features gmp-mpfr-sys/force-cross) ;;
+    *windows-gnu*) mflags+=(--features libm-test/build-mpfr) ;;
     aarch64*apple*) mflags+=(--features libm-test/build-mpfr) ;;
     aarch64*linux*) mflags+=(--features libm-test/build-mpfr) ;;
     i586*) mflags+=(--features libm-test/build-mpfr --features gmp-mpfr-sys/force-cross) ;;
diff --git a/libm/Cargo.toml b/libm/Cargo.toml
index f80715ff..521c745a 100644
--- a/libm/Cargo.toml
+++ b/libm/Cargo.toml
@@ -47,3 +47,5 @@ unexpected_cfgs = { level = "warn", check-cfg = [
   # compiler-builtins sets this feature, but we use it in `libm`
   'cfg(feature, values("compiler-builtins"))',
 ] }
+
+# TODO drop this line, it's just to poke CI that runs on libm changes