Starting work on full GN build

tools/clang/scripts/update.sh

Index: tools/clang/scripts/update.sh
diff --git a/tools/clang/scripts/update.sh b/tools/clang/scripts/update.sh
new file mode 100755
index 0000000000000000000000000000000000000000..d85deae23c349bdd6245c09093116655ef44a184
--- /dev/null
+++ b/tools/clang/scripts/update.sh
@@ -0,0 +1,724 @@
+#!/usr/bin/env bash
+# Copyright (c) 2012 The Chromium Authors. All rights reserved.
+# Use of this source code is governed by a BSD-style license that can be
+# found in the LICENSE file.
+
+# This script will check out llvm and clang into third_party/llvm and build it.
+
+# Do NOT CHANGE this if you don't know what you're doing -- see
+# https://code.google.com/p/chromium/wiki/UpdatingClang
+# Reverting problematic clang rolls is safe, though.
+CLANG_REVISION=241602
+
+# This is incremented when pushing a new build of Clang at the same revision.
+CLANG_SUB_REVISION=3
+
+PACKAGE_VERSION="${CLANG_REVISION}-${CLANG_SUB_REVISION}"
+
+THIS_DIR="$(dirname "${0}")"
+LLVM_DIR="${THIS_DIR}/../../../third_party/llvm"
+LLVM_BUILD_DIR="${LLVM_DIR}/../llvm-build/Release+Asserts"
+COMPILER_RT_BUILD_DIR="${LLVM_DIR}/../llvm-build/compiler-rt"
+LLVM_BOOTSTRAP_DIR="${LLVM_DIR}/../llvm-bootstrap"
+LLVM_BOOTSTRAP_INSTALL_DIR="${LLVM_DIR}/../llvm-bootstrap-install"
+CLANG_DIR="${LLVM_DIR}/tools/clang"
+COMPILER_RT_DIR="${LLVM_DIR}/compiler-rt"
+LIBCXX_DIR="${LLVM_DIR}/projects/libcxx"
+LIBCXXABI_DIR="${LLVM_DIR}/projects/libcxxabi"
+ANDROID_NDK_DIR="${THIS_DIR}/../../../third_party/android_tools/ndk"
+STAMP_FILE="${LLVM_DIR}/../llvm-build/cr_build_revision"
+CHROMIUM_TOOLS_DIR="${THIS_DIR}/.."
+BINUTILS_DIR="${THIS_DIR}/../../../third_party/binutils"
+
+ABS_CHROMIUM_TOOLS_DIR="${PWD}/${CHROMIUM_TOOLS_DIR}"
+ABS_LIBCXX_DIR="${PWD}/${LIBCXX_DIR}"
+ABS_LIBCXXABI_DIR="${PWD}/${LIBCXXABI_DIR}"
+ABS_LLVM_DIR="${PWD}/${LLVM_DIR}"
+ABS_LLVM_BUILD_DIR="${PWD}/${LLVM_BUILD_DIR}"
+ABS_COMPILER_RT_DIR="${PWD}/${COMPILER_RT_DIR}"
+ABS_BINUTILS_DIR="${PWD}/${BINUTILS_DIR}"
+
+# ${A:-a} returns $A if it's set, a else.
+LLVM_REPO_URL=${LLVM_URL:-https://llvm.org/svn/llvm-project}
+
+CDS_URL=https://commondatastorage.googleapis.com/chromium-browser-clang
+
+if [[ -z "$GYP_DEFINES" ]]; then
+  GYP_DEFINES=
+fi
+if [[ -z "$GYP_GENERATORS" ]]; then
+  GYP_GENERATORS=
+fi
+if [[ -z "$LLVM_DOWNLOAD_GOLD_PLUGIN" ]]; then
+  LLVM_DOWNLOAD_GOLD_PLUGIN=
+fi
+
+
+# Die if any command dies, error on undefined variable expansions.
+set -eu
+
+
+if [[ -n ${LLVM_FORCE_HEAD_REVISION:-''} ]]; then
+  # Use a real revision number rather than HEAD to make sure that the stamp file
+  # logic works.
+  CLANG_REVISION=$(svn info "$LLVM_REPO_URL" \
+      | grep 'Revision:' | awk '{ printf $2; }')
+  PACKAGE_VERSION="${CLANG_REVISION}-0"
+fi
+
+OS="$(uname -s)"
+
+# Parse command line options.
+if_needed=
+force_local_build=
+run_tests=
+bootstrap=
+with_android=yes
+chrome_tools="plugins;blink_gc_plugin"
+gcc_toolchain=
+with_patches=yes
+
+if [[ "${OS}" = "Darwin" ]]; then
+  with_android=
+fi
+
+while [[ $# > 0 ]]; do
+  case $1 in
+    --bootstrap)
+      bootstrap=yes
+      ;;
+    --if-needed)
+      if_needed=yes
+      ;;
+    --force-local-build)
+      force_local_build=yes
+      ;;
+    --print-revision)
+      if [[ -n ${LLVM_FORCE_HEAD_REVISION:-''} ]]; then
+        svn info "$LLVM_DIR" | grep 'Revision:' | awk '{ printf $2; }'
+      else
+        echo $PACKAGE_VERSION
+      fi
+      exit 0
+      ;;
+    --run-tests)
+      run_tests=yes
+      ;;
+    --without-android)
+      with_android=
+      ;;
+    --without-patches)
+      with_patches=
+      ;;
+    --with-chrome-tools)
+      shift
+      if [[ $# == 0 ]]; then
+        echo "--with-chrome-tools requires an argument."
+        exit 1
+      fi
+      chrome_tools=$1
+      ;;
+    --gcc-toolchain)
+      shift
+      if [[ $# == 0 ]]; then
+        echo "--gcc-toolchain requires an argument."
+        exit 1
+      fi
+      if [[ -x "$1/bin/gcc" ]]; then
+        gcc_toolchain=$1
+      else
+        echo "Invalid --gcc-toolchain: '$1'."
+        echo "'$1/bin/gcc' does not appear to be valid."
+        exit 1
+      fi
+      ;;
+
+    --help)
+      echo "usage: $0 [--force-local-build] [--if-needed] [--run-tests] "
+      echo "--bootstrap: First build clang with CC, then with itself."
+      echo "--force-local-build: Don't try to download prebuilt binaries."
+      echo "--if-needed: Download clang only if the script thinks it is needed."
+      echo "--run-tests: Run tests after building. Only for local builds."
+      echo "--print-revision: Print current clang revision and exit."
+      echo "--without-android: Don't build ASan Android runtime library."
+      echo "--with-chrome-tools: Select which chrome tools to build." \
+           "Defaults to plugins;blink_gc_plugin."
+      echo "    Example: --with-chrome-tools plugins;empty-string"
+      echo "--gcc-toolchain: Set the prefix for which GCC version should"
+      echo "    be used for building. For example, to use gcc in"
+      echo "    /opt/foo/bin/gcc, use '--gcc-toolchain '/opt/foo"
+      echo "--without-patches: Don't apply local patches."
+      echo
+      exit 1
+      ;;
+    *)
+      echo "Unknown argument: '$1'."
+      echo "Use --help for help."
+      exit 1
+      ;;
+  esac
+  shift
+done
+
+if [[ -n ${LLVM_FORCE_HEAD_REVISION:-''} ]]; then
+  force_local_build=yes
+
+  # Skip local patches when using HEAD: they probably don't apply anymore.
+  with_patches=
+
+  if ! [[ "$GYP_DEFINES" =~ .*OS=android.* ]]; then
+    # Only build the Android ASan rt when targetting Android.
+    with_android=
+  fi
+
+  LLVM_BUILD_TOOLS_DIR="${ABS_LLVM_DIR}/../llvm-build-tools"
+
+  if [[ "${OS}" == "Linux" ]] && [[ -z "${gcc_toolchain}" ]]; then
+    if [[ $(gcc -dumpversion) < "4.7.0" ]]; then
+      # We need a newer GCC version.
+      if [[ ! -e "${LLVM_BUILD_TOOLS_DIR}/gcc482" ]]; then
+        echo "Downloading pre-built GCC 4.8.2..."
+        mkdir -p "${LLVM_BUILD_TOOLS_DIR}"
+        curl --fail -L "${CDS_URL}/tools/gcc482.tgz" | \
+          tar zxf - -C "${LLVM_BUILD_TOOLS_DIR}"
+        echo Done
+      fi
+      gcc_toolchain="${LLVM_BUILD_TOOLS_DIR}/gcc482"
+    else
+      # Always set gcc_toolchain; llvm-symbolizer needs the bundled libstdc++.
+      gcc_toolchain="$(dirname $(dirname $(which gcc)))"
+    fi
+  fi
+
+  if [[ "${OS}" == "Linux" || "${OS}" == "Darwin" ]]; then
+    if [[ $(cmake --version | grep -Eo '[0-9.]+') < "3.0" ]]; then
+      # We need a newer CMake version.
+      if [[ ! -e "${LLVM_BUILD_TOOLS_DIR}/cmake310" ]]; then
+        echo "Downloading pre-built CMake 3.10..."
+        mkdir -p "${LLVM_BUILD_TOOLS_DIR}"
+        curl --fail -L "${CDS_URL}/tools/cmake310_${OS}.tgz" | \
+          tar zxf - -C "${LLVM_BUILD_TOOLS_DIR}"
+        echo Done
+      fi
+      export PATH="${LLVM_BUILD_TOOLS_DIR}/cmake310/bin:${PATH}"
+    fi
+  fi
+
+  echo "LLVM_FORCE_HEAD_REVISION was set; using r${CLANG_REVISION}"
+fi
+
+if [[ -n "$if_needed" ]]; then
+  if [[ "${OS}" == "Darwin" ]]; then
+    # clang is always used on Mac.
+    true
+  elif [[ "${OS}" == "Linux" ]]; then
+    # clang is also aways used on Linux.
+    true
+  elif [[ "$GYP_DEFINES" =~ .*(clang|tsan|asan|lsan|msan)=1.* ]]; then
+    # clang requested via $GYP_DEFINES.
+    true
+  elif [[ -d "${LLVM_BUILD_DIR}" ]]; then
+    # clang previously downloaded, keep it up-to-date.
+    # If you don't want this, delete third_party/llvm-build on your machine.
+    true
+  else
+    # clang wasn't needed, not doing anything.
+    exit 0
+  fi
+fi
+
+
+# Check if there's anything to be done, exit early if not.
+if [[ -f "${STAMP_FILE}" ]]; then
+  PREVIOUSLY_BUILT_REVISON=$(cat "${STAMP_FILE}")
+  if [[ -z "$force_local_build" ]] && \
+       [[ "${PREVIOUSLY_BUILT_REVISON}" = \
+          "${PACKAGE_VERSION}" ]]; then
+    echo "Clang already at ${PACKAGE_VERSION}"
+    exit 0
+  fi
+fi
+# To always force a new build if someone interrupts their build half way.
+rm -f "${STAMP_FILE}"
+
+
+if [[ -z "$force_local_build" ]]; then
+  # Check if there's a prebuilt binary and if so just fetch that. That's faster,
+  # and goma relies on having matching binary hashes on client and server too.
+  CDS_FILE="clang-${PACKAGE_VERSION}.tgz"
+  CDS_OUT_DIR=$(mktemp -d -t clang_download.XXXXXX)
+  CDS_OUTPUT="${CDS_OUT_DIR}/${CDS_FILE}"
+  if [ "${OS}" = "Linux" ]; then
+    CDS_FULL_URL="${CDS_URL}/Linux_x64/${CDS_FILE}"
+  elif [ "${OS}" = "Darwin" ]; then
+    CDS_FULL_URL="${CDS_URL}/Mac/${CDS_FILE}"
+  fi
+  echo Trying to download prebuilt clang
+  if which curl > /dev/null; then
+    curl -L --fail "${CDS_FULL_URL}" -o "${CDS_OUTPUT}" || \
+        rm -rf "${CDS_OUT_DIR}"
+  elif which wget > /dev/null; then
+    wget "${CDS_FULL_URL}" -O "${CDS_OUTPUT}" || rm -rf "${CDS_OUT_DIR}"
+  else
+    echo "Neither curl nor wget found. Please install one of these."
+    exit 1
+  fi
+  if [ -f "${CDS_OUTPUT}" ]; then
+    rm -rf "${LLVM_BUILD_DIR}"
+    mkdir -p "${LLVM_BUILD_DIR}"
+    tar -xzf "${CDS_OUTPUT}" -C "${LLVM_BUILD_DIR}"
+    echo clang "${PACKAGE_VERSION}" unpacked
+    echo "${PACKAGE_VERSION}" > "${STAMP_FILE}"
+    rm -rf "${CDS_OUT_DIR}"
+    # Download the gold plugin if requested to by an environment variable.
+    # This is used by the CFI ClusterFuzz bot.
+    if [[ -n "${LLVM_DOWNLOAD_GOLD_PLUGIN}" ]]; then
+      ${THIS_DIR}/../../../build/download_gold_plugin.py
+    fi
+    exit 0
+  else
+    echo Did not find prebuilt clang "${PACKAGE_VERSION}", building
+  fi
+fi
+
+if [[ -n "${with_android}" ]] && ! [[ -d "${ANDROID_NDK_DIR}" ]]; then
+  echo "Android NDK not found at ${ANDROID_NDK_DIR}"
+  echo "The Android NDK is needed to build a Clang whose -fsanitize=address"
+  echo "works on Android. See "
+  echo "http://code.google.com/p/chromium/wiki/AndroidBuildInstructions for how"
+  echo "to install the NDK, or pass --without-android."
+  exit 1
+fi
+
+# Check that cmake and ninja are available.
+if ! which cmake > /dev/null; then
+  echo "CMake needed to build clang; please install"
+  exit 1
+fi
+if ! which ninja > /dev/null; then
+  echo "ninja needed to build clang, please install"
+  exit 1
+fi
+
+echo Reverting previously patched files
+for i in \
+      "${CLANG_DIR}/test/Index/crash-recovery-modules.m" \
+      "${CLANG_DIR}/unittests/libclang/LibclangTest.cpp" \
+      "${COMPILER_RT_DIR}/lib/asan/asan_rtl.cc" \
+      "${COMPILER_RT_DIR}/test/asan/TestCases/Linux/new_array_cookie_test.cc" \
+      "${LLVM_DIR}/test/DebugInfo/gmlt.ll" \
+      "${LLVM_DIR}/lib/CodeGen/SpillPlacement.cpp" \
+      "${LLVM_DIR}/lib/CodeGen/SpillPlacement.h" \
+      "${LLVM_DIR}/lib/Transforms/Instrumentation/MemorySanitizer.cpp" \
+      "${CLANG_DIR}/test/Driver/env.c" \
+      "${CLANG_DIR}/lib/Frontend/InitPreprocessor.cpp" \
+      "${CLANG_DIR}/test/Frontend/exceptions.c" \
+      "${CLANG_DIR}/test/Preprocessor/predefined-exceptions.m" \
+      "${LLVM_DIR}/test/Bindings/Go/go.test" \
+      "${CLANG_DIR}/lib/Parse/ParseExpr.cpp" \
+      "${CLANG_DIR}/lib/Parse/ParseTemplate.cpp" \
+      "${CLANG_DIR}/lib/Sema/SemaDeclCXX.cpp" \
+      "${CLANG_DIR}/lib/Sema/SemaExprCXX.cpp" \
+      "${CLANG_DIR}/test/SemaCXX/default2.cpp" \
+      "${CLANG_DIR}/test/SemaCXX/typo-correction-delayed.cpp" \
+      "${COMPILER_RT_DIR}/lib/sanitizer_common/sanitizer_stoptheworld_linux_libcdep.cc" \
+      "${COMPILER_RT_DIR}/test/tsan/signal_segv_handler.cc" \
+      "${COMPILER_RT_DIR}/lib/sanitizer_common/sanitizer_coverage_libcdep.cc" \
+      "${COMPILER_RT_DIR}/cmake/config-ix.cmake" \
+      "${COMPILER_RT_DIR}/CMakeLists.txt" \
+      "${COMPILER_RT_DIR}/lib/ubsan/ubsan_platform.h" \
+      ; do
+  if [[ -e "${i}" ]]; then
+    rm -f "${i}"  # For unversioned files.
+    svn revert "${i}"
+  fi;
+done
+
+echo Remove the Clang tools shim dir
+CHROME_TOOLS_SHIM_DIR=${ABS_LLVM_DIR}/tools/chrometools
+rm -rfv ${CHROME_TOOLS_SHIM_DIR}
+
+echo Getting LLVM r"${CLANG_REVISION}" in "${LLVM_DIR}"
+if ! svn co --force "${LLVM_REPO_URL}/llvm/trunk@${CLANG_REVISION}" \
+                    "${LLVM_DIR}"; then
+  echo Checkout failed, retrying
+  rm -rf "${LLVM_DIR}"
+  svn co --force "${LLVM_REPO_URL}/llvm/trunk@${CLANG_REVISION}" "${LLVM_DIR}"
+fi
+
+echo Getting clang r"${CLANG_REVISION}" in "${CLANG_DIR}"
+svn co --force "${LLVM_REPO_URL}/cfe/trunk@${CLANG_REVISION}" "${CLANG_DIR}"
+
+# We have moved from building compiler-rt in the LLVM tree, to a separate
+# directory. Nuke any previous checkout to avoid building it.
+rm -rf "${LLVM_DIR}/projects/compiler-rt"
+
+echo Getting compiler-rt r"${CLANG_REVISION}" in "${COMPILER_RT_DIR}"
+svn co --force "${LLVM_REPO_URL}/compiler-rt/trunk@${CLANG_REVISION}" \
+               "${COMPILER_RT_DIR}"
+
+# clang needs a libc++ checkout, else -stdlib=libc++ won't find includes
+# (i.e. this is needed for bootstrap builds).
+if [ "${OS}" = "Darwin" ]; then
+  echo Getting libc++ r"${CLANG_REVISION}" in "${LIBCXX_DIR}"
+  svn co --force "${LLVM_REPO_URL}/libcxx/trunk@${CLANG_REVISION}" \
+                 "${LIBCXX_DIR}"
+fi
+
+# While we're bundling our own libc++ on OS X, we need to compile libc++abi
+# into it too (since OS X 10.6 doesn't have libc++abi.dylib either).
+if [ "${OS}" = "Darwin" ]; then
+  echo Getting libc++abi r"${CLANG_REVISION}" in "${LIBCXXABI_DIR}"
+  svn co --force "${LLVM_REPO_URL}/libcxxabi/trunk@${CLANG_REVISION}" \
+                 "${LIBCXXABI_DIR}"
+fi
+
+if [[ -n "$with_patches" ]]; then
+
+  # Apply patch for tests failing with --disable-pthreads (llvm.org/PR11974)
+  pushd "${CLANG_DIR}"
+  cat << 'EOF' |
+--- test/Index/crash-recovery-modules.m	(revision 202554)
++++ test/Index/crash-recovery-modules.m	(working copy)
+@@ -12,6 +12,8 @@
+ 
+ // REQUIRES: crash-recovery
+ // REQUIRES: shell
++// XFAIL: *
++//    (PR11974)
+ 
+ @import Crash;
+EOF
+patch -p0
+popd
+
+pushd "${CLANG_DIR}"
+cat << 'EOF' |
+--- unittests/libclang/LibclangTest.cpp (revision 215949)
++++ unittests/libclang/LibclangTest.cpp (working copy)
+@@ -431,7 +431,7 @@
+   EXPECT_EQ(0U, clang_getNumDiagnostics(ClangTU));
+ }
+
+-TEST_F(LibclangReparseTest, ReparseWithModule) {
++TEST_F(LibclangReparseTest, DISABLED_ReparseWithModule) {
+   const char *HeaderTop = "#ifndef H\n#define H\nstruct Foo { int bar;";
+   const char *HeaderBottom = "\n};\n#endif\n";
+   const char *MFile = "#include \"HeaderFile.h\"\nint main() {"
+EOF
+  patch -p0
+  popd
+
+  # This Go bindings test doesn't work after the bootstrap build on Linux. (PR21552)
+  pushd "${LLVM_DIR}"
+  cat << 'EOF' |
+--- test/Bindings/Go/go.test    (revision 223109)
++++ test/Bindings/Go/go.test    (working copy)
+@@ -1,3 +1,3 @@
+-; RUN: llvm-go test llvm.org/llvm/bindings/go/llvm
++; RUN: true
+ 
+ ; REQUIRES: shell
+EOF
+  patch -p0
+  popd
+
+  # The UBSan run-time, which is now bundled with the ASan run-time, doesn't work
+  # on Mac OS X 10.8 (PR23539).
+  pushd "${COMPILER_RT_DIR}"
+  cat << 'EOF' |
+Index: CMakeLists.txt
+===================================================================
+--- CMakeLists.txt	(revision 241602)
++++ CMakeLists.txt	(working copy)
+@@ -305,6 +305,7 @@
+       list(APPEND SANITIZER_COMMON_SUPPORTED_OS iossim)
+     endif()
+   endif()
++  set(SANITIZER_MIN_OSX_VERSION "10.7")
+   if(SANITIZER_MIN_OSX_VERSION VERSION_LESS "10.7")
+     message(FATAL_ERROR "Too old OS X version: ${SANITIZER_MIN_OSX_VERSION}")
+   endif()
+EOF
+  patch -p0
+  popd
+
+fi
+
+# Echo all commands.
+set -x
+
+# Set default values for CC and CXX if they're not set in the environment.
+CC=${CC:-cc}
+CXX=${CXX:-c++}
+
+if [[ -n "${gcc_toolchain}" ]]; then
+  # Use the specified gcc installation for building.
+  CC="$gcc_toolchain/bin/gcc"
+  CXX="$gcc_toolchain/bin/g++"
+  # Set LD_LIBRARY_PATH to make auxiliary targets (tablegen, bootstrap compiler,
+  # etc.) find the .so.
+  export LD_LIBRARY_PATH="$(dirname $(${CXX} -print-file-name=libstdc++.so.6))"
+fi
+
+CFLAGS=""
+CXXFLAGS=""
+LDFLAGS=""
+
+# LLVM uses C++11 starting in llvm 3.5. On Linux, this means libstdc++4.7+ is
+# needed, on OS X it requires libc++. clang only automatically links to libc++
+# when targeting OS X 10.9+, so add stdlib=libc++ explicitly so clang can run on
+# OS X versions as old as 10.7.
+# TODO(thakis): Some bots are still on 10.6 (nacl...), so for now bundle
+# libc++.dylib.  Remove this once all bots are on 10.7+, then use
+# -DLLVM_ENABLE_LIBCXX=ON and change deployment_target to 10.7.
+deployment_target=""
+
+if [ "${OS}" = "Darwin" ]; then
+  # When building on 10.9, /usr/include usually doesn't exist, and while
+  # Xcode's clang automatically sets a sysroot, self-built clangs don't.
+  CFLAGS="-isysroot $(xcrun --show-sdk-path)"
+  CXXFLAGS="-stdlib=libc++ -nostdinc++ -I${ABS_LIBCXX_DIR}/include ${CFLAGS}"
+
+  if [[ -n "${bootstrap}" ]]; then
+    deployment_target=10.6
+  fi
+fi
+
+# Build bootstrap clang if requested.
+if [[ -n "${bootstrap}" ]]; then
+  ABS_INSTALL_DIR="${PWD}/${LLVM_BOOTSTRAP_INSTALL_DIR}"
+  echo "Building bootstrap compiler"
+  mkdir -p "${LLVM_BOOTSTRAP_DIR}"
+  pushd "${LLVM_BOOTSTRAP_DIR}"
+
+  cmake -GNinja \
+      -DCMAKE_BUILD_TYPE=Release \
+      -DLLVM_ENABLE_ASSERTIONS=ON \
+      -DLLVM_TARGETS_TO_BUILD=host \
+      -DLLVM_ENABLE_THREADS=OFF \
+      -DCMAKE_INSTALL_PREFIX="${ABS_INSTALL_DIR}" \
+      -DCMAKE_C_COMPILER="${CC}" \
+      -DCMAKE_CXX_COMPILER="${CXX}" \
+      -DCMAKE_C_FLAGS="${CFLAGS}" \
+      -DCMAKE_CXX_FLAGS="${CXXFLAGS}" \
+      ../llvm
+
+  ninja
+  if [[ -n "${run_tests}" ]]; then
+    ninja check-all
+  fi
+
+  ninja install
+  if [[ -n "${gcc_toolchain}" ]]; then
+    # Copy that gcc's stdlibc++.so.6 to the build dir, so the bootstrap
+    # compiler can start.
+    cp -v "$(${CXX} -print-file-name=libstdc++.so.6)" \
+      "${ABS_INSTALL_DIR}/lib/"
+  fi
+
+  popd
+  CC="${ABS_INSTALL_DIR}/bin/clang"
+  CXX="${ABS_INSTALL_DIR}/bin/clang++"
+
+  if [[ -n "${gcc_toolchain}" ]]; then
+    # Tell the bootstrap compiler to use a specific gcc prefix to search
+    # for standard library headers and shared object file.
+    CFLAGS="--gcc-toolchain=${gcc_toolchain}"
+    CXXFLAGS="--gcc-toolchain=${gcc_toolchain}"
+  fi
+
+  echo "Building final compiler"
+fi
+
+# Build clang (in a separate directory).
+# The clang bots have this path hardcoded in built/scripts/slave/compile.py,
+# so if you change it you also need to change these links.
+mkdir -p "${LLVM_BUILD_DIR}"
+pushd "${LLVM_BUILD_DIR}"
+
+# Build libc++.dylib while some bots are still on OS X 10.6.
+if [ "${OS}" = "Darwin" ]; then
+  rm -rf libcxxbuild
+  LIBCXXFLAGS="-O3 -std=c++11 -fstrict-aliasing"
+
+  # libcxx and libcxxabi both have a file stdexcept.cpp, so put their .o files
+  # into different subdirectories.
+  mkdir -p libcxxbuild/libcxx
+  pushd libcxxbuild/libcxx
+  ${CXX:-c++} -c ${CXXFLAGS} ${LIBCXXFLAGS} "${ABS_LIBCXX_DIR}"/src/*.cpp
+  popd
+
+  mkdir -p libcxxbuild/libcxxabi
+  pushd libcxxbuild/libcxxabi
+  ${CXX:-c++} -c ${CXXFLAGS} ${LIBCXXFLAGS} "${ABS_LIBCXXABI_DIR}"/src/*.cpp -I"${ABS_LIBCXXABI_DIR}/include"
+  popd
+
+  pushd libcxxbuild
+  ${CC:-cc} libcxx/*.o libcxxabi/*.o -o libc++.1.dylib -dynamiclib \
+    -nodefaultlibs -current_version 1 -compatibility_version 1 \
+    -lSystem -install_name @executable_path/libc++.dylib \
+    -Wl,-unexported_symbols_list,${ABS_LIBCXX_DIR}/lib/libc++unexp.exp \
+    -Wl,-force_symbols_not_weak_list,${ABS_LIBCXX_DIR}/lib/notweak.exp \
+    -Wl,-force_symbols_weak_list,${ABS_LIBCXX_DIR}/lib/weak.exp
+  ln -sf libc++.1.dylib libc++.dylib
+  popd
+  LDFLAGS+="-stdlib=libc++ -L${PWD}/libcxxbuild"
+
+  if [[ -n "${bootstrap}" ]]; then
+    # Now that the libc++ headers have been installed and libc++.dylib is built,
+    # delete the libc++ checkout again so that it's not part of the main
+    # build below -- the libc++(abi) tests don't pass on OS X in bootstrap
+    # builds (http://llvm.org/PR24068)
+    rm -rf "${ABS_LIBCXX_DIR}"
+    rm -rf "${ABS_LIBCXXABI_DIR}"
+    CXXFLAGS="-stdlib=libc++ -nostdinc++ -I${ABS_INSTALL_DIR}/include/c++/v1 ${CFLAGS}"
+  fi
+fi
+
+# Find the binutils include dir for the gold plugin.
+BINUTILS_INCDIR=""
+if [ "${OS}" = "Linux" ]; then
+  BINUTILS_INCDIR="${ABS_BINUTILS_DIR}/Linux_x64/Release/include"
+fi
+
+
+# If building at head, define a macro that plugins can use for #ifdefing
+# out code that builds at head, but not at CLANG_REVISION or vice versa.
+if [[ -n ${LLVM_FORCE_HEAD_REVISION:-''} ]]; then
+  CFLAGS="${CFLAGS} -DLLVM_FORCE_HEAD_REVISION"
+  CXXFLAGS="${CXXFLAGS} -DLLVM_FORCE_HEAD_REVISION"
+fi
+
+# Hook the Chromium tools into the LLVM build. Several Chromium tools have
+# dependencies on LLVM/Clang libraries. The LLVM build detects implicit tools
+# in the tools subdirectory, so install a shim CMakeLists.txt that forwards to
+# the real directory for the Chromium tools.
+# Note that the shim directory name intentionally has no _ or _. The implicit
+# tool detection logic munges them in a weird way.
+mkdir -v ${CHROME_TOOLS_SHIM_DIR}
+cat > ${CHROME_TOOLS_SHIM_DIR}/CMakeLists.txt << EOF
+# Since tools/clang isn't actually a subdirectory, use the two argument version
+# to specify where build artifacts go. CMake doesn't allow reusing the same
+# binary dir for multiple source dirs, so the build artifacts have to go into a
+# subdirectory...
+add_subdirectory(\${CHROMIUM_TOOLS_SRC} \${CMAKE_CURRENT_BINARY_DIR}/a)
+EOF
+rm -fv CMakeCache.txt
+MACOSX_DEPLOYMENT_TARGET=${deployment_target} cmake -GNinja \
+    -DCMAKE_BUILD_TYPE=Release \
+    -DLLVM_ENABLE_ASSERTIONS=ON \
+    -DLLVM_ENABLE_THREADS=OFF \
+    -DLLVM_BINUTILS_INCDIR="${BINUTILS_INCDIR}" \
+    -DCMAKE_C_COMPILER="${CC}" \
+    -DCMAKE_CXX_COMPILER="${CXX}" \
+    -DCMAKE_C_FLAGS="${CFLAGS}" \
+    -DCMAKE_CXX_FLAGS="${CXXFLAGS}" \
+    -DCMAKE_EXE_LINKER_FLAGS="${LDFLAGS}" \
+    -DCMAKE_SHARED_LINKER_FLAGS="${LDFLAGS}" \
+    -DCMAKE_MODULE_LINKER_FLAGS="${LDFLAGS}" \
+    -DCMAKE_INSTALL_PREFIX="${ABS_LLVM_BUILD_DIR}" \
+    -DCHROMIUM_TOOLS_SRC="${ABS_CHROMIUM_TOOLS_DIR}" \
+    -DCHROMIUM_TOOLS="${chrome_tools}" \
+    "${ABS_LLVM_DIR}"
+env
+
+if [[ -n "${gcc_toolchain}" ]]; then
+  # Copy in the right stdlibc++.so.6 so clang can start.
+  mkdir -p lib
+  cp -v "$(${CXX} ${CXXFLAGS} -print-file-name=libstdc++.so.6)" lib/
+fi
+
+ninja
+# If any Chromium tools were built, install those now.
+if [[ -n "${chrome_tools}" ]]; then
+  ninja cr-install
+fi
+
+STRIP_FLAGS=
+if [ "${OS}" = "Darwin" ]; then
+  # See http://crbug.com/256342
+  STRIP_FLAGS=-x
+
+  cp libcxxbuild/libc++.1.dylib bin/
+fi
+strip ${STRIP_FLAGS} bin/clang
+popd
+
+# Build compiler-rt out-of-tree.
+mkdir -p "${COMPILER_RT_BUILD_DIR}"
+pushd "${COMPILER_RT_BUILD_DIR}"
+
+rm -fv CMakeCache.txt
+MACOSX_DEPLOYMENT_TARGET=${deployment_target} cmake -GNinja \
+    -DCMAKE_BUILD_TYPE=Release \
+    -DLLVM_ENABLE_ASSERTIONS=ON \
+    -DLLVM_ENABLE_THREADS=OFF \
+    -DCMAKE_C_COMPILER="${CC}" \
+    -DCMAKE_CXX_COMPILER="${CXX}" \
+    -DLLVM_CONFIG_PATH="${ABS_LLVM_BUILD_DIR}/bin/llvm-config" \
+    "${ABS_COMPILER_RT_DIR}"
+
+ninja
+
+# Copy selected output to the main tree.
+# Darwin doesn't support cp --parents, so pipe through tar instead.
+CLANG_VERSION=$("${ABS_LLVM_BUILD_DIR}/bin/clang" --version | \
+     sed -ne 's/clang version \([0-9]\.[0-9]\.[0-9]\).*/\1/p')
+ABS_LLVM_CLANG_LIB_DIR="${ABS_LLVM_BUILD_DIR}/lib/clang/${CLANG_VERSION}"
+tar -c *blacklist.txt | tar -C ${ABS_LLVM_CLANG_LIB_DIR} -xv
+tar -c include/sanitizer | tar -C ${ABS_LLVM_CLANG_LIB_DIR} -xv
+if [[ "${OS}" = "Darwin" ]]; then
+  tar -c lib/darwin | tar -C ${ABS_LLVM_CLANG_LIB_DIR} -xv
+else
+  tar -c lib/linux | tar -C ${ABS_LLVM_CLANG_LIB_DIR} -xv
+fi
+
+popd
+
+if [[ -n "${with_android}" ]]; then
+  # Make a standalone Android toolchain.
+  ${ANDROID_NDK_DIR}/build/tools/make-standalone-toolchain.sh \
+      --platform=android-19 \
+      --install-dir="${LLVM_BUILD_DIR}/android-toolchain" \
+      --system=linux-x86_64 \
+      --stl=stlport \
+      --toolchain=arm-linux-androideabi-4.9
+
+  # Android NDK r9d copies a broken unwind.h into the toolchain, see
+  # http://crbug.com/357890
+  rm -v "${LLVM_BUILD_DIR}"/android-toolchain/include/c++/*/unwind.h
+
+  # Build ASan runtime for Android in a separate build tree.
+  mkdir -p ${LLVM_BUILD_DIR}/android
+  pushd ${LLVM_BUILD_DIR}/android
+  rm -fv CMakeCache.txt
+  MACOSX_DEPLOYMENT_TARGET=${deployment_target} cmake -GNinja \
+      -DCMAKE_BUILD_TYPE=Release \
+      -DLLVM_ENABLE_ASSERTIONS=ON \
+      -DLLVM_ENABLE_THREADS=OFF \
+      -DCMAKE_C_COMPILER=${PWD}/../bin/clang \
+      -DCMAKE_CXX_COMPILER=${PWD}/../bin/clang++ \
+      -DLLVM_CONFIG_PATH=${PWD}/../bin/llvm-config \
+      -DCMAKE_C_FLAGS="--target=arm-linux-androideabi --sysroot=${PWD}/../android-toolchain/sysroot -B${PWD}/../android-toolchain" \
+      -DCMAKE_CXX_FLAGS="--target=arm-linux-androideabi --sysroot=${PWD}/../android-toolchain/sysroot -B${PWD}/../android-toolchain" \
+      -DANDROID=1 \
+      "${ABS_COMPILER_RT_DIR}"
+  ninja libclang_rt.asan-arm-android.so
+
+  # And copy it into the main build tree.
+  cp "$(find -name libclang_rt.asan-arm-android.so)" "${ABS_LLVM_CLANG_LIB_DIR}/lib/linux/"
+  popd
+fi
+
+if [[ -n "$run_tests" || -n "${LLVM_FORCE_HEAD_REVISION:-''}" ]]; then
+  # Run Chrome tool tests.
+  ninja -C "${LLVM_BUILD_DIR}" cr-check-all
+fi
+if [[ -n "$run_tests" ]]; then
+  # Run the LLVM and Clang tests.
+  ninja -C "${LLVM_BUILD_DIR}" check-all
+fi
+
+# After everything is done, log success for this revision.
+echo "${PACKAGE_VERSION}" > "${STAMP_FILE}"