https://bugs.freedesktop.org/show_bug.cgi?id=83205
--- Comment #5 from Clément Guérin geecko.dev@free.fr --- Alright, so I compiled lib32-mesa-git from here http://pkgbuild.com/~lcarlier/mesa-git/ with the two patches for radeonsi. It doesn't crash anymore with HyperZ enabled.
I can't be 100% sure though, because Steam managed to update the game just before I launched it. A very minor upgrade, so I assume the issue is fixed.
I guess it's time to reenable HyperZ by default, because it's the only issue I ever had with all the games I tried so far. I will try Brütal Legend now.