reproduce:
        # apt-get install sparse
        # sparse version: v0.6.4-66-g0196afe1
        # https://git.kernel.org/pub/scm/linux/kernel/git/tip/tip.git/commit/?id=bacde25dbbad6180b434332ad829b9e2f8064a56
        git remote add tip https://git.kernel.org/pub/scm/linux/kernel/git/tip/tip.git
        git fetch --no-tags tip x86/core
        git checkout bacde25dbbad6180b434332ad829b9e2f8064a56
        # save the config file
        mkdir build_dir && cp config build_dir/.config
        make W=1 C=1 CF='-fdiagnostic-prefix -D__CHECK_ENDIAN__ -fmax-errors=unlimited -fmax-warnings=unlimited' O=build_dir ARCH=x86_64 olddefconfig
        make W=1 C=1 CF='-fdiagnostic-prefix -D__CHECK_ENDIAN__ -fmax-errors=unlimited -fmax-warnings=unlimited' O=build_dir ARCH=x86_64 SHELL=/bin/bash arch/x86/kernel/cpu/