Build locally your own optimized version of LLVM/Clang

UpdateLLVM.bash

#! /bin/bash

source_dir="" # Define this, example(this usually should be the device with the fastest Read perf): ${HOME:?}/git/llvm
build_dir="" # Define this, example(preferably a different device which can be slower): /ssd/llvm-build
install_prefix="" # Define this, example: /usr/local/llvm
release_branch="release_60"

update_project() {
  local -r dir="${1:?}"
  local -r branch="${2:?}"
  (
    cd "${dir}" || exit 1
    git fetch origin "${branch}"
    git clean -fdx
    git reset --hard origin/"${branch}"
  )
}

install_llvm() {
  mkdir -p "${build_dir:?}"
  cd "${build_dir}" || exit 1

  rm -rf ./*
  if [ -z "${LLVM_FIRST_RUN}" ]; then
    cmake \
      -DCMAKE_BUILD_TYPE=Release \
      -DCMAKE_C_COMPILER="${install_prefix:?}/bin/clang" \
      -DCMAKE_CXX_COMPILER="${install_prefix:?}/bin/clang++" \
      -DCMAKE_RANLIB="${install_prefix:?}/bin/llvm-ranlib" \
      -DCMAKE_AR="${install_prefix:?}/bin/llvm-ar" \
      -DCMAKE_CXX_FLAGS="-O3 -mtune=native -march=native -m64 -mavx -fomit-frame-pointer -isystem /usr/include/ncurses" \
      -DCMAKE_C_FLAGS="-O3 -mtune=native -march=native -m64 -mavx -fomit-frame-pointer -isystem /usr/include/ncurses" \
      -DCMAKE_EXE_LINKER_FLAGS="-Wl,--as-needed -Wl,--build-id=sha1" \
      -DCMAKE_MODULE_LINKER_FLAGS="-Wl,--as-needed -Wl,--build-id=sha1" \
      -DCMAKE_SHARED_LINKER_FLAGS="-Wl,--as-needed -Wl,--build-id=sha1" \
      -DLLVM_TARGETS_TO_BUILD=Native \
      -DENABLE_LINKER_BUILD_ID=ON \
      -DLLVM_ENABLE_PIC=ON \
      -DLLVM_ENABLE_LLD=ON \
      -DCMAKE_INTERPROCEDURAL_OPTIMIZATION=ON \
      -DLLVM_ENABLE_LTO=Thin \
      -DCMAKE_POLICY_DEFAULT_CMP0069=NEW \
      -DLLVM_ENABLE_RTTI=ON \
      -DLLVM_INCLUDE_TESTS=OFF \
      -DLLVM_INCLUDE_EXAMPLES=OFF \
      -DPYTHON_EXECUTABLE:FILEPATH=/usr/bin/python \
      -DCMAKE_INSTALL_PREFIX="${install_prefix:?}" \
      -C "${source_dir}/tools/clang/cmake/caches/PGO.cmake" \
      -G Ninja "${source_dir}"

    ninja stage2
  else
    cmake \
      -DCMAKE_BUILD_TYPE=Release \
      -DCMAKE_C_COMPILER=/usr/bin/gcc \
      -DCMAKE_CXX_COMPILER=/usr/bin/g++ \
      -DCMAKE_RANLIB=/usr/bin/ranlib \
      -DCMAKE_AR=/usr/bin/ar \
      -DCMAKE_POLICY_DEFAULT_CMP0069=NEW \
      -DLLVM_ENABLE_RTTI=ON \
      -DLLVM_INCLUDE_TESTS=OFF \
      -DLLVM_INCLUDE_EXAMPLES=OFF \
      -DPYTHON_EXECUTABLE:FILEPATH=/usr/bin/python \
      -DCMAKE_INSTALL_PREFIX="${install_prefix:?}" \
      -G Ninja "${source_dir}"
  fi

  ninja install
}

main() {
  (
    cd "$(dirname "${source_dir:?}")" || exit 1
    if [ -z "${LLVM_FIRST_RUN}" ]; then
      update_project "llvm/"                         "master" # stable
      update_project "llvm/tools/clang"              "master" # google/stable
      update_project "llvm/projects/compiler-rt"     "master" # google/stable
      update_project "llvm/tools/clang/tools/extra"  "master" # stable
      update_project "llvm/tools/lld"                "master" # release_[latest_version]
      update_project "llvm/tools/lldb"               "master" # release_[latest_version]
    else
      update_project "llvm/"                         "${release_branch:?}"
      update_project "llvm/tools/clang"              "${release_branch:?}"
      update_project "llvm/projects/compiler-rt"     "${release_branch:?}"
      update_project "llvm/tools/clang/tools/extra"  "${release_branch:?}"
      update_project "llvm/tools/lld"                "${release_branch:?}"
      update_project "llvm/tools/lldb"               "${release_branch:?}"
    fi

    install_llvm
  )
}

main "$@"