I just built Mesa master using this llvm 9 snapshot:
The Witcher 3 in Wine+dxvk started hanging (causing GPU reset).
Hardware: Sapphire Pulse AMD Vega 56.
With llvm 8, and it's not hanging.
I think this was an issue with the linking for tessellation being changed in LLVM, which was fixed by the following radv MR:
Given the age, I'm closing. Feel free to reopen if still occurring.