https://bugs.freedesktop.org/show_bug.cgi?id=110214
--- Comment #25 from Michel Dänzer michel@daenzer.net --- Just to make sure, you always restart the X server between building a Mesa commit and testing xterm against it, right? And you're making sure that the X server picks up your self-built radeonsi_dri.so for glamor?
If so, since that commit doesn't seem to affect the xterm issue, let's assume for now that it's separate. Please file a new report about the GTK issue, also against radeonsi, with the information from git bisect.