[CI] Build and cache seprate Clang and GCC builds of LLVM

Code compiled with Clang cannot be linked with GCC due to
incompatibilities related to lambda closure capture lists.

This patch builds and caches LLVM with Clang to be used
with the Clang Release build and with GCC to be used with
the GCC Debug build of CIRCT.

The ABI issue and a potential fix is being tracked here:
itanium-cxx-abi/cxx-abi#141

.github/workflows/buildAndTest.yml

@@ -124,6 +124,13 @@ jobs:
     runs-on: ubuntu-latest
     container:
       image: ghcr.io/circt/images/circt-ci-build:20220216182244
+    strategy:
+      matrix:
+        compiler:
+          - cc: clang
+            cxx: clang++
+          - cc: gcc
+            cxx: g++
     steps:
       # Clone the CIRCT repo and its submodules. Do shallow clone to save clone
       # time.
@@ -140,22 +147,22 @@ jobs:
 
       - name: Get workflow spec hash
         id: get-workflow-hash
-        run: echo "::set-output name=hash::$(md5sum $GITHUB_WORKSPACE/.github/workflows/buildAndTest.yml)"
+        run: echo "::set-output name=hash::$(md5sum $GITHUB_WORKSPACE/.github/workflows/buildAndTest.yml | awk '{print $1}')"
 
       # Try to fetch LLVM from the cache.
-      - name: Cache LLVM
+      - name: Cache LLVM (${{ matrix.compiler.cc }})
         id: cache-llvm
         uses: actions/cache@v2
         with:
           path: |
             llvm/build
             llvm/install
-          key: ${{ runner.os }}-llvm-${{ steps.get-llvm-hash.outputs.hash }}-${{ steps.get-workflow-hash.outputs.hash }}
+          key: ${{ runner.os }}-llvm-${{ steps.get-llvm-hash.outputs.hash }}-${{ steps.get-workflow-hash.outputs.hash }}-${{ matrix.compiler.cc }}-${{ matrix.compiler.cxx }}
 
       # Build LLVM if we didn't hit in the cache.
       - name: Rebuild and Install LLVM
         if: steps.cache-llvm.outputs.cache-hit != 'true'
-        run: utils/build-llvm.sh
+        run: utils/build-llvm.sh build install Release ${{ matrix.compiler.cc }} ${{ matrix.compiler.cxx }}
 
 
     # Installing the results into the cache is an action which is automatically
@@ -224,21 +231,38 @@ jobs:
         run: echo "::set-output name=hash::$(md5sum $GITHUB_WORKSPACE/.github/workflows/buildAndTest.yml)"
 
       # Try to fetch LLVM from the cache.
-      - name: Cache LLVM
-        id: cache-llvm
+      - name: Cache LLVM (Clang)
+        id: cache-llvm-clang
         uses: actions/cache@v2
         with:
           path: |
-            llvm/build
-            llvm/install
-          key: ${{ runner.os }}-llvm-${{ steps.get-llvm-hash.outputs.hash }}-${{ steps.get-workflow-hash.outputs.hash }}
+            llvm/build-clang
+            llvm/install-clang
+          key: ${{ runner.os }}-llvm-${{ steps.get-llvm-hash.outputs.hash }}-${{ steps.get-workflow-hash.outputs.hash }}-clang
 
       # Build LLVM if we didn't hit in the cache. Even though we build it in
       # the previous job, there is a low chance that it'll have been evicted by
       # the time we get here.
-      - name: Rebuild and Install LLVM
-        if: steps.cache-llvm.outputs.cache-hit != 'true'
-        run: utils/build-llvm.sh
+      - name: Rebuild and Install LLVM (Clang)
+        if: steps.cache-llvm-clang.outputs.cache-hit != 'true'
+        run: utils/build-llvm.sh build-clang install-clang Release clang clang++
+
+      # Try to fetch LLVM from the cache.
+      - name: Cache LLVM (GCC)
+        id: cache-llvm-gcc
+        uses: actions/cache@v2
+        with:
+          path: |
+            llvm/build-gcc
+            llvm/install-gcc
+          key: ${{ runner.os }}-llvm-${{ steps.get-llvm-hash.outputs.hash }}-${{ steps.get-workflow-hash.outputs.hash }}-gcc
+
+      # Build LLVM if we didn't hit in the cache. Even though we build it in
+      # the previous job, there is a low chance that it'll have been evicted by
+      # the time we get here.
+      - name: Rebuild and Install LLVM (GCC)
+        if: steps.cache-llvm-gcc.outputs.cache-hit != 'true'
+        run: utils/build-llvm.sh build-gcc install-gcc Release gcc g++
 
       # --------
       # Build and test CIRCT in both debug and release mode.
@@ -257,12 +281,12 @@ jobs:
             -DBUILD_SHARED_LIBS=ON \
             -DCMAKE_BUILD_TYPE=Release \
             -DLLVM_ENABLE_ASSERTIONS=OFF \
-            -DMLIR_DIR=../llvm/install/lib/cmake/mlir/ \
-            -DLLVM_DIR=../llvm/install/lib/cmake/llvm/ \
+            -DMLIR_DIR=`pwd`/../llvm/install-clang/lib/cmake/mlir \
+            -DLLVM_DIR=`pwd`/../llvm/install-clang/lib/cmake/llvm \
             -DLLVM_USE_LINKER=lld \
             -DCMAKE_C_COMPILER=clang \
             -DCMAKE_CXX_COMPILER=clang++ \
-            -DLLVM_EXTERNAL_LIT=`pwd`/../llvm/build/bin/llvm-lit \
+            -DLLVM_EXTERNAL_LIT=`pwd`/../llvm/build-clang/bin/llvm-lit \
             -DCMAKE_EXPORT_COMPILE_COMMANDS=ON
           make check-circt -j$(nproc)
           make circt-doc
@@ -275,12 +299,12 @@ jobs:
           cmake .. \
             -DCMAKE_BUILD_TYPE=Debug \
             -DLLVM_ENABLE_ASSERTIONS=ON \
-            -DMLIR_DIR=../llvm/install/lib/cmake/mlir/ \
-            -DLLVM_DIR=../llvm/install/lib/cmake/llvm/ \
+            -DMLIR_DIR=`pwd`/../llvm/install-gcc/lib/cmake/mlir/ \
+            -DLLVM_DIR=`pwd`/../llvm/install-gcc/lib/cmake/llvm/ \
             -DLLVM_USE_LINKER=lld \
             -DCMAKE_C_COMPILER=gcc \
             -DCMAKE_CXX_COMPILER=g++ \
-            -DLLVM_EXTERNAL_LIT=`pwd`/../llvm/build/bin/llvm-lit
+            -DLLVM_EXTERNAL_LIT=`pwd`/../llvm/build-gcc/bin/llvm-lit
           make check-circt -j$(nproc)
           make circt-doc
 

utils/build-llvm.sh

@@ -15,16 +15,18 @@
 BUILD_DIR=${1:-"build"}
 INSTALL_DIR=${2:-"install"}
 BUILD_TYPE=${3:-"Release"}
-EXTRA_ARGS=${@:4}
+CC=${4:-"clang"}
+CXX=${5:-"clang++"}
+EXTRA_ARGS=${@:6}
 
 mkdir -p llvm/$BUILD_DIR
 mkdir -p llvm/$INSTALL_DIR
 cd llvm/$BUILD_DIR
 cmake ../llvm \
   -DBUILD_SHARED_LIBS=ON \
   -DCMAKE_BUILD_TYPE=$BUILD_TYPE \
-  -DCMAKE_C_COMPILER=clang \
-  -DCMAKE_CXX_COMPILER=clang++ \
+  -DCMAKE_C_COMPILER=$CC \
+  -DCMAKE_CXX_COMPILER=$CXX \
   -DCMAKE_INSTALL_PREFIX=../$INSTALL_DIR \
   -DLLVM_BUILD_EXAMPLES=OFF \
   -DLLVM_ENABLE_ASSERTIONS=ON \