[clang][ci] Move libc++ testing into the main PR pipeline (#93318)

Following the discussion in
#93233 (comment),
this patch merges `clang-ci` pipeline into main `GitHub Pull Requests`
pipeline. `clang-ci` enables additional test coverage for Clang by
compiling it, and then using it to compile and test libc++, libc++abi,
and libunwind in C++03, C++26, and Clang Modules modes.

Additional work we skip and total time savings we should see:
1. Checking out the repo to generate the clang-ci pipeline (2 minutes)
2. Building Clang (3.5 minutes)
3. Uploading the artifacts once, then downloading them 3 times and
unpacking 3 times (0.5 minutes)

Note that because previously-split jobs for each mode are now under a
single Linux job, it now takes around 8 minutes more see the Linux CI
results despite total time savings.

The primary goal of this patch is to reduce the load of CI by removing
duplicated work. I consider this goal achieved. I could keep the job
parallelism we had (3 libc++ jobs depending on a main Linux job), but I
don't consider it worth the effort and opportunity cost, because
parallelism is not helping once the pool of builders is fully
subscribed.

Author: Endilll

.ci/generate-buildkite-pipeline-premerge

@@ -85,6 +85,22 @@ function compute-projects-to-test() {
   done
 }
 
+function compute-runtimes-to-test() {
+  projects=${@}
+  for project in ${projects}; do
+    case ${project} in
+    clang)
+      for p in libcxx libcxxabi libunwind; do
+        echo $p
+      done
+    ;;
+    *)
+      # Nothing to do
+    ;;
+    esac
+  done
+}
+
 function add-dependencies() {
   projects=${@}
   for project in ${projects}; do
@@ -178,6 +194,15 @@ function check-targets() {
     cross-project-tests)
       echo "check-cross-project"
     ;;
+    libcxx)
+      echo "check-cxx"
+    ;;
+    libcxxabi)
+      echo "check-cxxabi"
+    ;;
+    libunwind)
+      echo "check-unwind"
+    ;;
     lldb)
       echo "check-all" # TODO: check-lldb may not include all the LLDB tests?
     ;;
@@ -207,17 +232,6 @@ if echo "$modified_dirs" | grep -q -E "^(libcxx|libcxxabi|libunwind|runtimes|cma
 EOF
 fi
 
-# If clang changed.
-if echo "$modified_dirs" | grep -q -E "^(clang)$"; then
-  cat <<EOF
-- trigger: "clang-ci"
-  build:
-    message: "${buildMessage}"
-    commit: "${BUILDKITE_COMMIT}"
-    branch: "${BUILDKITE_BRANCH}"
-EOF
-fi
-
 # Generic pipeline for projects that have not defined custom steps.
 #
 # Individual projects should instead define the pre-commit CI tests that suits their
@@ -231,6 +245,10 @@ linux_projects_to_test=$(exclude-linux $(compute-projects-to-test ${modified_pro
 linux_check_targets=$(check-targets ${linux_projects_to_test} | sort | uniq)
 linux_projects=$(add-dependencies ${linux_projects_to_test} | sort | uniq)
 
+linux_runtimes_to_test=$(compute-runtimes-to-test ${linux_projects_to_test})
+linux_runtime_check_targets=$(check-targets ${linux_runtimes_to_test} | sort | uniq)
+linux_runtimes=$(echo ${linux_runtimes_to_test} | sort | uniq)
+
 windows_projects_to_test=$(exclude-windows $(compute-projects-to-test ${modified_projects}))
 windows_check_targets=$(check-targets ${windows_projects_to_test} | sort | uniq)
 windows_projects=$(add-dependencies ${windows_projects_to_test} | sort | uniq)
@@ -255,7 +273,7 @@ if [[ "${linux_projects}" != "" ]]; then
     CC: 'clang'
     CXX: 'clang++'
   commands:
-  - './.ci/monolithic-linux.sh "$(echo ${linux_projects} | tr ' ' ';')" "$(echo ${linux_check_targets})"'
+  - './.ci/monolithic-linux.sh "$(echo ${linux_projects} | tr ' ' ';')" "$(echo ${linux_check_targets})" "$(echo ${linux_runtimes} | tr ' ' ';')" "$(echo ${linux_runtime_check_targets})"'
 EOF
 fi
 

.ci/monolithic-linux.sh

@@ -18,6 +18,7 @@ set -o pipefail
 
 MONOREPO_ROOT="${MONOREPO_ROOT:="$(git rev-parse --show-toplevel)"}"
 BUILD_DIR="${BUILD_DIR:=${MONOREPO_ROOT}/build}"
+INSTALL_DIR="${BUILD_DIR}/install"
 rm -rf "${BUILD_DIR}"
 
 ccache --zero-stats
@@ -49,8 +50,79 @@ cmake -S "${MONOREPO_ROOT}"/llvm -B "${BUILD_DIR}" \
       -D LLVM_ENABLE_LLD=ON \
       -D CMAKE_CXX_FLAGS=-gmlt \
       -D LLVM_CCACHE_BUILD=ON \
-      -D MLIR_ENABLE_BINDINGS_PYTHON=ON
+      -D MLIR_ENABLE_BINDINGS_PYTHON=ON \
+      -D CMAKE_INSTALL_PREFIX="${INSTALL_DIR}"
 
 echo "--- ninja"
 # Targets are not escaped as they are passed as separate arguments.
 ninja -C "${BUILD_DIR}" -k 0 ${targets}
+
+runtimes="${3}"
+runtime_targets="${4}"
+
+# Compiling runtimes with just-built Clang and running their tests
+# as an additional testing for Clang.
+if [[ "${runtimes}" != "" ]]; then
+  if [[ "${runtime_targets}" == "" ]]; then
+    echo "Runtimes to build are specified, but targets are not."
+    exit 1
+  fi
+
+  echo "--- ninja install-clang"
+
+  ninja -C ${BUILD_DIR} install-clang install-clang-resource-headers
+
+  RUNTIMES_BUILD_DIR="${MONOREPO_ROOT}/build-runtimes"
+  INSTALL_DIR="${BUILD_DIR}/install"
+  mkdir -p ${RUNTIMES_BUILD_DIR}
+
+  echo "--- cmake runtimes C++03"
+
+  cmake -S "${MONOREPO_ROOT}/runtimes" -B "${RUNTIMES_BUILD_DIR}" -GNinja \
+      -D CMAKE_C_COMPILER="${INSTALL_DIR}/bin/clang" \
+      -D CMAKE_CXX_COMPILER="${INSTALL_DIR}/bin/clang++" \
+      -D LLVM_ENABLE_RUNTIMES="${runtimes}" \
+      -D LIBCXX_CXX_ABI=libcxxabi \
+      -D CMAKE_BUILD_TYPE=RelWithDebInfo \
+      -D CMAKE_INSTALL_PREFIX="${INSTALL_DIR}" \
+      -D LIBCXX_TEST_PARAMS="std=c++03" \
+      -D LIBCXXABI_TEST_PARAMS="std=c++03"
+
+  echo "--- ninja runtimes C++03"
+
+  ninja -vC "${RUNTIMES_BUILD_DIR}" ${runtime_targets}
+
+  echo "--- cmake runtimes C++26"
+
+  rm -rf "${RUNTIMES_BUILD_DIR}"
+  cmake -S "${MONOREPO_ROOT}/runtimes" -B "${RUNTIMES_BUILD_DIR}" -GNinja \
+      -D CMAKE_C_COMPILER="${INSTALL_DIR}/bin/clang" \
+      -D CMAKE_CXX_COMPILER="${INSTALL_DIR}/bin/clang++" \
+      -D LLVM_ENABLE_RUNTIMES="${runtimes}" \
+      -D LIBCXX_CXX_ABI=libcxxabi \
+      -D CMAKE_BUILD_TYPE=RelWithDebInfo \
+      -D CMAKE_INSTALL_PREFIX="${INSTALL_DIR}" \
+      -D LIBCXX_TEST_PARAMS="std=c++26" \
+      -D LIBCXXABI_TEST_PARAMS="std=c++26"
+
+  echo "--- ninja runtimes C++26"
+
+  ninja -vC "${RUNTIMES_BUILD_DIR}" ${runtime_targets}
+
+  echo "--- cmake runtimes clang modules"
+
+  rm -rf "${RUNTIMES_BUILD_DIR}"
+  cmake -S "${MONOREPO_ROOT}/runtimes" -B "${RUNTIMES_BUILD_DIR}" -GNinja \
+      -D CMAKE_C_COMPILER="${INSTALL_DIR}/bin/clang" \
+      -D CMAKE_CXX_COMPILER="${INSTALL_DIR}/bin/clang++" \
+      -D LLVM_ENABLE_RUNTIMES="${runtimes}" \
+      -D LIBCXX_CXX_ABI=libcxxabi \
+      -D CMAKE_BUILD_TYPE=RelWithDebInfo \
+      -D CMAKE_INSTALL_PREFIX="${INSTALL_DIR}" \
+      -D LIBCXX_TEST_PARAMS="enable_modules=clang" \
+      -D LIBCXXABI_TEST_PARAMS="enable_modules=clang"
+
+  echo "--- ninja runtimes clang modules"
+  
+  ninja -vC "${RUNTIMES_BUILD_DIR}" ${runtime_targets}
+fi