Unigine Superposition stuck on loading

This is a regression, because it was working few weeks ago just fine with normal loading times.

Now it is just stack on the loading screen. Both Medium and Extreme presets.

It loads in 48-51 seconds on radeonsi. On zink I would expect a little more, but maybe max 120 seconds.

Instead it is stuck at least for 10 minutes, with no progress being made.

top shows 102% CPU usage non-stop.

Sample gdb back traces (on the main thread):

(gdb) bt
#0  0x00007f27368caf18 in _tc_sync.constprop.0 () from /home/user/mesa-git/installdir/build-amd64-opt/install/lib/dri/zink_dri.so
#1  0x00007f27364665a6 in fence_finish.lto_priv () from /home/user/mesa-git/installdir/build-amd64-opt/install/lib/dri/zink_dri.so
#2  0x00007f2735af6a01 in st_client_wait_sync.lto_priv () from /home/user/mesa-git/installdir/build-amd64-opt/install/lib/dri/zink_dri.so
#3  0x00007f2735cd10e1 in _mesa_ClientWaitSync () from /home/user/mesa-git/installdir/build-amd64-opt/install/lib/dri/zink_dri.so
#4  0x00007f27fa53567a in ?? () from /home/user/Downloads/Unigine_Superposition-1.1/bin/libUnigine_x64.so
#5  0x00007f27fa553565 in ?? () from /home/user/Downloads/Unigine_Superposition-1.1/bin/libUnigine_x64.so
#6  0x00007f27f9a73061 in ?? () from /home/user/Downloads/Unigine_Superposition-1.1/bin/libUnigine_x64.so
#7  0x00007f27f9fcc7df in ?? () from /home/user/Downloads/Unigine_Superposition-1.1/bin/libUnigine_x64.so
#8  0x00007f27fa1de32b in ?? () from /home/user/Downloads/Unigine_Superposition-1.1/bin/libUnigine_x64.so
#9  0x00007f27fa1dfeaa in ?? () from /home/user/Downloads/Unigine_Superposition-1.1/bin/libUnigine_x64.so
#10 0x00007f27fa1cd1e9 in ?? () from /home/user/Downloads/Unigine_Superposition-1.1/bin/libUnigine_x64.so
#11 0x00007f27fa1c34f5 in ?? () from /home/user/Downloads/Unigine_Superposition-1.1/bin/libUnigine_x64.so
#12 0x00007f27fa1d17bc in ?? () from /home/user/Downloads/Unigine_Superposition-1.1/bin/libUnigine_x64.so
#13 0x00007f27fa1c992a in ?? () from /home/user/Downloads/Unigine_Superposition-1.1/bin/libUnigine_x64.so
#14 0x00007f27fa1d420c in ?? () from /home/user/Downloads/Unigine_Superposition-1.1/bin/libUnigine_x64.so
#15 0x00007f27fa26f397 in ?? () from /home/user/Downloads/Unigine_Superposition-1.1/bin/libUnigine_x64.so
#16 0x00007f27f96cc75f in ?? () from /home/user/Downloads/Unigine_Superposition-1.1/bin/libUnigine_x64.so
#17 0x00007f27fa5192b3 in ?? () from /home/user/Downloads/Unigine_Superposition-1.1/bin/libUnigine_x64.so
#18 0x00007f27f9602228 in ?? () from /home/user/Downloads/Unigine_Superposition-1.1/bin/libUnigine_x64.so
#19 0x0000000000417155 in main ()
(gdb) 

(gdb) bt
0x00007f2735cd0661 in _mesa_unref_sync_object () from /home/user/mesa-git/installdir/build-amd64-opt/install/lib/dri/zink_dri.so
(gdb) bt
#0  0x00007f2735cd0661 in _mesa_unref_sync_object () from /home/user/mesa-git/installdir/build-amd64-opt/install/lib/dri/zink_dri.so
#1  0x00007f2735cd1127 in _mesa_ClientWaitSync () from /home/user/mesa-git/installdir/build-amd64-opt/install/lib/dri/zink_dri.so
...

(gdb) bt
#0  0x00007f2735af69bc in st_client_wait_sync.lto_priv () from /home/user/mesa-git/installdir/build-amd64-opt/install/lib/dri/zink_dri.so
#1  0x00007f2735cd10e1 in _mesa_ClientWaitSync () from /home/user/mesa-git/installdir/build-amd64-opt/install/lib/dri/zink_dri.so
...

(gdb) bt
#0  0x00007f27364544a0 in fence_reference.lto_priv () from /home/user/mesa-git/installdir/build-amd64-opt/install/lib/dri/zink_dri.so
#1  0x00007f2735af69e3 in st_client_wait_sync.lto_priv () from /home/user/mesa-git/installdir/build-amd64-opt/install/lib/dri/zink_dri.so
#2  0x00007f2735cd10e1 in _mesa_ClientWaitSync () from /home/user/mesa-git/installdir/build-amd64-opt/install/lib/dri/zink_dri.so

perf top -t ... shows something like this (main thread only):

Overhead  Shared Object           Symbol
  37.31%  zink_dri.so             [.] st_client_wait_sync.lto_priv.0
  21.12%  zink_dri.so             [.] fence_reference.lto_priv.0
  17.32%  zink_dri.so             [.] _mesa_unref_sync_object
  11.15%  zink_dri.so             [.] _mesa_get_and_ref_sync
   3.75%  zink_dri.so             [.] fence_finish.lto_priv.0
   2.58%  zink_dri.so             [.] _tc_sync.constprop.0
   1.58%  zink_dri.so             [.] _mesa_ClientWaitSync
   1.40%  zink_dri.so             [.] set_search.lto_priv.0
   1.30%  zink_dri.so             [.] _mesa_hash_pointer
   0.89%  zink_dri.so             [.] _mesa_key_pointer_equal
   0.75%  zink_dri.so             [.] st_check_sync.lto_priv.0
   0.50%  libGLdispatch.so.0.0.0  [.] glClientWaitSync
   0.34%  libUnigine_x64.so       [.] 0x0000000001503665
   0.01%  [kernel]                [k] change_protection

zink-wip @ f28d48ed

AMD Radeon R9 Fury X (FIJI, GFX8) @ radv ACO.