diff --git a/.github/workflows/clang.yml b/.github/workflows/clang.yml
new file mode 100644
index 000000000000..22f03df2969a
--- /dev/null
+++ b/.github/workflows/clang.yml
@@ -0,0 +1,60 @@
+name: Clang builds
+
+on: [push]
+
+jobs:
+  test_clang:
+    strategy:
+      fail-fast: false
+      matrix:
+        name:
+          - ubuntu18.04-gcc5
+          - ubuntu18.04-clang8
+          - ubuntu18.04-clang8
+          - win2019-clang
+          - macos10.14-xcode11
+        include:
+          - name: ubuntu18.04-gcc5
+            os: ubuntu-18.04
+            compiler: gcc
+            compiler-version: 5
+          - name: ubuntu18.04-clang8
+            os: ubuntu-18.04
+            compiler: clang
+            compiler-version: 8
+          - name: win2019-clang
+            os: windows-2019
+            compiler: clang
+            compiler-version: latest
+          - name: macos10.14-xcode11
+            os: macos-10.14
+            compiler: xcode
+            compiler-version: 11
+    name: ${{ matrix.name }}
+    runs-on: ${{ matrix.os }}
+    steps:
+      - uses: actions/checkout@v1
+        with:
+          fetch-depth: 1
+      - name: Install deps
+        shell: bash
+        run: .github/workflows/utils/install_deps.sh ${{ runner.os }} ${{ matrix.compiler }} ${{ matrix.compiler-version }}
+      - if: runner.os == 'Linux'
+        run: echo "::set-env name=extra_cmake_args::-DLLVM_USE_LINKER=gold"
+      - name: configure
+        shell: bash
+        run: |
+          mkdir build
+          cd build
+          cmake -GNinja \
+                -DLLVM_ENABLE_PROJECTS="clang;clang-tools-extra" \
+                -DCMAKE_BUILD_TYPE=Release \
+                -DLLVM_ENABLE_ASSERTIONS:BOOL=ON \
+                ${extra_cmake_args:-} \
+                ../llvm
+      - name: build
+        run: ninja -C build
+      - name: test
+        run: ninja -C build check
+      - name: test-clang
+        run: ninja -C build check-clang
diff --git a/.github/workflows/libcxx.yml b/.github/workflows/libcxx.yml
new file mode 100644
index 000000000000..cece2849f182
--- /dev/null
+++ b/.github/workflows/libcxx.yml
@@ -0,0 +1,58 @@
+name: LibCXX builds
+
+on: [push]
+
+jobs:
+  test_libcxx:
+    strategy:
+      fail-fast: false
+      matrix:
+        name:
+          - ubuntu18.04-clang8-cxx03
+          - ubuntu18.04-clang8-cxx11
+          - macos10.14-xcode11-cxx11
+        include:
+          - name: ubuntu18.04-clang8-cxx03
+            os: ubuntu-18.04
+            compiler: clang
+            compiler-version: 8
+            cxx-std: c++03
+          - name: ubuntu18.04-clang8-cxx11
+            os: ubuntu-18.04
+            compiler: clang
+            compiler-version: 8
+            cxx-std: c++11
+          - name: macos10.14-xcode11-cxx11
+            os: macos-10.14
+            compiler: xcode
+            compiler-version: 11
+            cxx-std: c++11
+    name: ${{ matrix.name }}
+    runs-on: ${{ matrix.os }}
+    steps:
+      - uses: actions/checkout@v1
+        with:
+          fetch-depth: 1
+      - name: Install deps
+        shell: bash
+        run: .github/workflows/utils/install_deps.sh ${{ runner.os }} ${{ matrix.compiler }} ${{ matrix.compiler-version }}
+      - name: configure
+        shell: bash
+        run: |
+          echo $PATH
+          mkdir build
+          cd build
+          cmake -GNinja \
+                -DLLVM_ENABLE_PROJECTS="libcxx;libcxxabi;libunwind" \
+                -DLLVM_LIT_ARGS="-sv --show-unsupported --show-xfail --param=std=${{ matrix.cxx-std }}" \
+                ../llvm
+      - name: build libcxxabi
+        run: ninja -C build cxxabi
+      - name: build libcxxabi
+        run: ninja -C build cxx
+      - name: test libcxxabi
+        run: ninja -C build check-libcxxabi
+      - name: test libcxx
+        run: ninja -C build check-libcxx
+#      - name: test abilist
+#        run: ninja -C build check-cxx-abilist
diff --git a/.github/workflows/utils/install_deps.sh b/.github/workflows/utils/install_deps.sh
new file mode 100755
index 000000000000..b4bb0c7f7114
--- /dev/null
+++ b/.github/workflows/utils/install_deps.sh
@@ -0,0 +1,28 @@
+#!/bin/bash
+set -e
+set -u
+
+os_kind=$1
+compiler=$2
+compiler_version=$3
+
+if [[ $os_kind == 'Linux' ]]; then
+  if [[ $compiler = gcc ]]; then
+    compiler_pkg="g++-${compiler_version}"
+    compiler_cxx="g++"
+  elif [[ $compiler = clang ]]; then
+    compiler_pkg="${compiler}-${compiler_version}"
+    compiler_cxx="clang++"
+  fi
+  sudo apt-get install -y ninja-build "${compiler_pkg}"
+  echo "::set-env name=CC::${compiler}-${compiler_version}"
+  echo "::set-env name=CXX::${compiler_cxx}-${compiler_version}"
+
+elif [[ $os_kind == 'macOS' ]]; then
+  brew install ninja
+  sudo xcode-select -switch "/Applications/Xcode_${compiler_version}.app"
+  echo "::set-env name=CC::clang"
+  echo "::set-env name=CXX::clang++"
+elif [[ $os_kind == 'Windows' ]]; then
+  powershell.exe -command "& .github\workflows\utils\install_deps_windows.ps1"
+fi
diff --git a/.github/workflows/utils/install_deps_windows.ps1 b/.github/workflows/utils/install_deps_windows.ps1
new file mode 100644
index 000000000000..1671ca109108
--- /dev/null
+++ b/.github/workflows/utils/install_deps_windows.ps1
@@ -0,0 +1,13 @@
+# Powershell script
+
+iex (new-object net.webclient).downloadstring('https://get.scoop.sh')
+scoop install ninja
+scoop install llvm
+
+.\.github\workflows\utils\vs_setup.bat -arch=amd64
+
+# Remove link.exe from git-bash, as it conflicts with msvc link.exe...
+del c:\PROGRA~1\Git\usr\bin\link.exe
+
+echo "::set-env name=CC::clang-cl"
+echo "::set-env name=CXX::clang-cl"
diff --git a/.github/workflows/utils/vs_setup.bat b/.github/workflows/utils/vs_setup.bat
new file mode 100755
index 000000000000..750ce69561fa
--- /dev/null
+++ b/.github/workflows/utils/vs_setup.bat
@@ -0,0 +1,15 @@
+@echo off
+setlocal
+
+:: From https://github.com/microsoft/vswhere/wiki/Find-VC
+for /f "usebackq tokens=*" %%i in (`"%ProgramFiles(x86)%\Microsoft Visual Studio\Installer\vswhere.exe" -latest -property installationPath`) do (
+  set InstallDir=%%i
+)
+
+:: Setup environment
+call "%InstallDir%\Common7\Tools\vsdevcmd.bat" %*
+
+:: Echo all env vars as github runner commands, so they persist for subsequent steps.
+for /f "tokens=1,2 delims==" %%a in ('set') do (
+  echo ::set-env name=%%a::%%b
+)