diff --git a/.github/workflows/check-in-tree-build.yml b/.github/workflows/check-in-tree-build.yml
new file mode 100644
index 00000000..1fa5ee5a
--- /dev/null
+++ b/.github/workflows/check-in-tree-build.yml
@@ -0,0 +1,72 @@
+name: In-tree build
+
+on:
+  push:
+    branches:
+      - 'ocl-open-*'
+    paths-ignore: # no need to check build for:
+      - 'docs/**' # documentation
+      - '**.md'   # README
+  pull_request:
+    branches:
+      - 'ocl-open-*'
+    paths-ignore: # no need to check build for:
+      - 'docs/**' # documentation
+      - '**.md'   # README
+  schedule:
+    # Weekly build on Mondays
+    # Ideally, we might want to simplify our regular nightly build as we
+    # probably don't need every configuration to be built every day: most of
+    # them are only necessary in pre-commits to avoid breakages
+    - cron: 0 0 * * 0
+
+env:
+  LLVM_VERSION: 12
+
+jobs:
+  build_and_test_linux:
+    name: Linux
+    strategy:
+      matrix:
+        build_type: [Release]
+        include:
+          - build_type: Release
+      fail-fast: false
+    runs-on: ubuntu-18.04
+    steps:
+      - name: setup git config
+        run: |
+          git config --global user.email "<>"
+          git config --global user.name "GitHub Actions Bot"
+      - name: Checkout LLVM sources
+        uses: actions/checkout@v2
+        with:
+          repository: llvm/llvm-project
+          ref: release/12.x
+          path: llvm-project
+      - name:  Checkout the translator sources
+        uses: actions/checkout@v2
+        with:
+          repository: KhronosGroup/SPIRV-LLVM-Translator
+          ref: llvm_release_120
+          path: llvm-project/SPIRV-LLVM-Translator
+      - name:  Checkout opencl-clang sources
+        uses: actions/checkout@v2
+        with:
+          path: llvm-project/opencl-clang
+      - name: Configure
+        run: |
+          mkdir build && cd build
+          cmake ${{ github.workspace }}/llvm-project/llvm \
+            -DLLVM_ENABLE_PROJECTS="clang" \
+            -DLLVM_EXTERNAL_PROJECTS="llvm-spirv;opencl-clang" \
+            -DLLVM_EXTERNAL_LLVM_SPIRV_SOURCE_DIR=${{ github.workspace }}/llvm-project/SPIRV-LLVM-Translator \
+            -DLLVM_EXTERNAL_OPENCL_CLANG_SOURCE_DIR=${{ github.workspace }}/llvm-project/opencl-clang \
+            -DCMAKE_BUILD_TYPE=${{ matrix.build_type }} \
+            -DLLVM_TARGETS_TO_BUILD="X86" \
+            -G "Unix Makefiles"
+      - name: Build
+        run: |
+          cd build
+          
+          make opencl-clang -j2