When the llvm-lib extension is updated, the following changes occur in Xorg (excerpts from Xorg.0.log).
With older llvm-lib (version 10.0.0 by Juanito):
[ 24.357] (II) Loading sub module "glamoregl"
[ 24.357] (II) LoadModule: "glamoregl"
[ 24.357] (II) Loading /usr/local/lib/xorg/modules/libglamoregl.so
[ 24.373] (II) Module glamoregl: vendor="X.Org Foundation"
[ 24.373] compiled for 1.20.8, module version = 1.0.1
[ 24.373] ABI class: X.Org ANSI C Emulation, version 0.4
[ 25.443] (II) modeset(0): glamor X acceleration enabled on V3D 4.2
[ 25.443] (II) modeset(0): glamor initialized
....
[ 25.673] (II) modeset(0): [DRI2] Setup complete
[ 25.673] (II) modeset(0): [DRI2] DRI driver: vc4
[ 25.673] (II) modeset(0): [DRI2] VDPAU driver: vc4
....
[ 25.677] (II) Initializing extension GLX
[ 25.757] (II) AIGLX: Loaded and initialized vc4
[ 25.757] (II) GLX: Initialized DRI2 GL provider for screen 0
With new version (version 13.0.1 by polikuo):
[ 26.395] (II) Loading sub module "glamoregl"
[ 26.395] (II) LoadModule: "glamoregl"
[ 26.396] (II) Loading /usr/local/lib/xorg/modules/libglamoregl.so
[ 26.411] (II) Module glamoregl: vendor="X.Org Foundation"
[ 26.411] compiled for 1.20.8, module version = 1.0.1
[ 26.411] ABI class: X.Org ANSI C Emulation, version 0.4
[ 26.425] couldn't get display device
[ 26.425] (EE) modeset(0): glamor initialization failed
[ 26.425] (II) modeset(0): ShadowFB: preferred NO, enabled NO
.....
[ 26.532] (II) Initializing extension GLX
[ 26.532] (II) AIGLX: Screen 0 is not DRI2 capable
[ 26.532] (EE) AIGLX error: dlopen of /usr/local/lib/dri/swrast_dri.so failed (/usr/local/lib/dri/swrast_dri.so: cannot open shared object file: No such file or directory)
[ 26.532] (EE) AIGLX error: unable to load driver swrast
[ 26.532] (EE) GLX: could not load software renderer
[ 26.532] (II) GLX: no usable GL providers found for screen 0