Comment # 2 on bug 982177 from Iaroslav Andrusiak

It is normal, xorg.log just does not show dri3 usage.

you can check dri 3 with

LIBGL_DEBUG=verbose glxgears
libGL: pci id for fd 4: 1002:665c, driver radeonsi
libGL: OpenDriver: trying /usr/lib64/dri/tls/radeonsi_dri.so
libGL: OpenDriver: trying /usr/lib64/dri/radeonsi_dri.so
ATTENTION: default value of option vblank_mode overridden by environment.
libGL: Using DRI3 for screen 0