reproduce (this is a W=1 build):
        # https://git.kernel.org/pub/scm/linux/kernel/git/jolsa/perf.git/commit/?id=1e0ad55e88bddb17e85b4b7c4ba933f3b98ecca0
        git remote add jolsa-perf https://git.kernel.org/pub/scm/linux/kernel/git/jolsa/perf.git
        git fetch --no-tags jolsa-perf bpf/single_direct_ops
        git checkout 1e0ad55e88bddb17e85b4b7c4ba933f3b98ecca0
        # apt-get install sparse
        # sparse version: v0.6.4-71-g610d841d

        # 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 samples/ftrace/