redhat-rpm-config/brp-llvm-compile-lto-elf

#!/usr/bin/bash -eu


if [ -z "$RPM_BUILD_ROOT" ] || [ "$RPM_BUILD_ROOT" = "/" ]; then
	exit 0
fi

CLANG_FLAGS=$@
NCPUS=${RPM_BUILD_NCPUS:-1}

check_convert_bitcode () {
  local file_name=$(realpath ${1})
  local file_type=$(file ${file_name})

  shift
  CLANG_FLAGS="$@"

  if [[ "${file_type}" == *"LLVM IR bitcode"* ]]; then
    # check for an indication that the bitcode was
    # compiled with -flto
    llvm-bcanalyzer -dump ${file_name} | grep -xP '.*\-flto((?!-fno-lto).)*' 2>&1 > /dev/null
    if [ $? -eq 0 ]; then
      echo "Compiling LLVM bitcode file ${file_name}."
      clang ${CLANG_FLAGS} -fno-lto -Wno-unused-command-line-argument \
        -x ir ${file_name} -c -o ${file_name}
    fi
  elif [[ "${file_type}" == *"current ar archive"* ]]; then
    echo "Unpacking ar archive ${file_name} to check for LLVM bitcode components."
    # create archive stage for objects
    local archive_stage=$(mktemp -d)
    local archive=${file_name}
    pushd ${archive_stage}
    ar x ${archive}
    for archived_file in $(find -not -type d); do
      check_convert_bitcode ${archived_file} ${CLANG_FLAGS}
      echo "Repacking ${archived_file} into ${archive}."
      ar r ${archive} ${archived_file}
    done
    popd
  fi
}

echo "Checking for LLVM bitcode artifacts"
export -f check_convert_bitcode
find "$RPM_BUILD_ROOT" -type f -name "*.[ao]" -print0 | \
  xargs -0 -r -n1 -P$NCPUS sh -c "check_convert_bitcode \$@ $CLANG_FLAGS" ARG0