https://bugs.freedesktop.org/show_bug.cgi?id=80827
--- Comment #1 from Grzegorz Kowal custos.mentis@gmail.com --- With mesa from today's git the corruptions appear on the whole screen, like in the attached image (see full_screen_corruptions.png).
After quick bisecting, it looks like commit "radeonsi: Use dma_copy when possible for si_blit." (5d5c20920e0e570742a497aa047e99a2fa3c04f2) is responsible for that. When reverted, the full screen corruptions disappear, but window menu corruptions still persist.