reproduce:
        # apt-get install sparse
        # sparse version: v0.6.4-39-gce1a6720-dirty
        # https://github.com/rgushchin/linux/commit/1b638f41428889e8e7ab15b64939d9ceeeabfbd5
        git remote add rgushchin https://github.com/rgushchin/linux.git
        git fetch --no-tags rgushchin kmem_performance.1
        git checkout 1b638f41428889e8e7ab15b64939d9ceeeabfbd5
        # save the config file
        mkdir build_dir && cp config build_dir/.config
        make W=1 C=1 CF='-fdiagnostic-prefix -D__CHECK_ENDIAN__' O=build_dir ARCH=x86_64 olddefconfig
        make W=1 C=1 CF='-fdiagnostic-prefix -D__CHECK_ENDIAN__' O=build_dir ARCH=x86_64 SHELL=/bin/bash