grep LLVM /var/log/Xorg.0.log
[    29.423] (EE) AIGLX error: dlopen of /usr/lib/dri/r300_dri.so failed (libLLVM-8.so: cannot open shared object file: No such file or directory)
[    29.424] (EE) AIGLX error: dlopen of /usr/lib/dri/swrast_dri.so failed (libLLVM-8.so: cannot open shared object file: No such file or directory)

ldd /usr/lib/dri/r300_dri.so 
        linux-gate.so.1 (0xb7f26000)
        libdrm.so.2 => /usr/lib/libdrm.so.2 (0xb6836000)
        libLLVM-8.so => not found
        libexpat.so.1 => /usr/lib/libexpat.so.1 (0xb680a000)
        libdl.so.2 => /usr/lib/libdl.so.2 (0xb6804000)
        libsensors.so.5 => /usr/lib/libsensors.so.5 (0xb67f3000)
        libdrm_radeon.so.1 => /usr/lib/libdrm_radeon.so.1 (0xb67e4000)
        libelf.so.1 => /usr/lib/libelf.so.1 (0xb67c6000)
        libdrm_amdgpu.so.1 => /usr/lib/libdrm_amdgpu.so.1 (0xb67b9000)
        libdrm_nouveau.so.2 => /usr/lib/libdrm_nouveau.so.2 (0xb67ae000)
        libglapi.so.0 => /usr/lib/libglapi.so.0 (0xb678d000)
        libz.so.1 => /usr/lib/libz.so.1 (0xb6773000)
        libstdc++.so.6 => /usr/lib/libstdc++.so.6 (0xb6595000)
        libm.so.6 => /usr/lib/libm.so.6 (0xb64c3000)
        libgcc_s.so.1 => /usr/lib/libgcc_s.so.1 (0xb64a6000)
        libpthread.so.0 => /usr/lib/libpthread.so.0 (0xb6483000)
        libc.so.6 => /usr/lib/libc.so.6 (0xb62d3000)
        /usr/lib/ld-linux.so.2 (0xb7f27000)

ls /usr/lib/libLLVM*
/usr/lib/libLLVM-9.0.0.so  /usr/lib/libLLVM-9.so  /usr/lib/libLLVM.so