Created attachment 141472 [details]
This can be reproduced reliably using the attached apitrace.
OpenGL renderer string: Radeon RX Vega (VEGA10, DRM 3.23.0, 4.15.5-gentoo, LLVM 6.0.0)
OpenGL core profile version string: 4.5 (Core Profile) Mesa 18.3.0-devel (git-1c7a2433b2)
GS_EMIT without shader outputs seems to cause GPU hangs. Radeonsi generates shaders with GS_EMIT without writing shader outputs when geometry shader outputs are optimized out.
a potential fix: https://lists.freedesktop.org/archives/mesa-dev/2018-September/205848.html
piglit test: https://lists.freedesktop.org/archives/piglit/2018-September/025092.html
Fixed by commit e24a4e05c7a7b9f3a06fa55284d6258ceff44fdd