(In reply to comment #2)
> I get no lockup either, but I do see the same GPUVM protection faults:
> 
>  radeon 0000:01:00.0:   VM_CONTEXT1_PROTECTION_FAULT_ADDR   0x0FF00819
> 
> The FF bits make me suspect bits 32-4x of the GPUVM address are getting
> clobbered, maybe because of the LLVM backend generating invalid shader code.

I've found similar bug with incorrect high part of the address and the problem
was that llvm backend uses S_ADD/SUB_I32 for lowering 64-bit integer add/sub,
but it should use _U32 versions instead. I was going to send the patch but the
fix is trivial, basically just replace all uses of S_ADD/SUB_I32 with
S_ADD/SUB_U32. I'm not sure if you are hitting the same issue though.