You sure this isn't a driver bug? I haven't ever seen this before.
Works fine on my Polaris.

It could be a driver bug, but interestingly it's not specific to aco or llvm - happens in both. May be amdgpu bug then? I can report it to Mesa/radv first.
Not all driver issues are necessarily compiler-related, could just be a general problem with RADV+Navi.
Does AMDVLK render coreectly?
Let me try amdvlk, I haven't built it in a long time.
amdvlk renders fine.

Interesting, if I load an older save and then load that save, the corruption goes away.
Closing since nobody seems to be able to reproduce this.
Nothing extracted yet.
I noticed, that in The Witcher 3 I'm getting some rectangular graphical corruptions in the second world of Through Time and Space. Disabling vignetting removes the corruptions.
Here is the save of that location: tw3_save.tar.xz.zip
Note: all attached files are really tar.xz, but with added .zip to allow Github attaching.
Software information
The Witcher 3 GOTY, max settings, ambient occlusion: HBAO+, hairworks disabled, depth of field disabled.
System information
Corruption happens regardless of using aco or llvm.
Apitrace file(s)
Renderdoc frame: https://ufile.io/8aej0kbz
Log files
dxvk_logs.tar.xz.zip
If it's really a Mesa issue, I can open upstream bug.