Created attachment 140941 [details]
Probably affected compute shader

Hello,

a regression that affects OpControlBarrier instructions in compute shaders causes major rendering issues in Final Fantasy XV. The attached shader seems to be the one running into this issue.

In short, DXVK translates sync_g_t instructions to the following:

    OpControlBarrier Workgroup, Workgroup, WorkgroupMemory | AcquireRelease

This currently does not work as expected. Interestingly, inserting an additional OpMemoryBarrier seems to fix the problem:

    OpMemoryBarrier Workgroup, WorkgroupMemory | AcquireRelease
    OpControlBarrier Workgroup, Workgroup, WorkgroupMemory | AcquireRelease

While this is closer to what glslang emits for equivalent GLSL barriers, emitting the extra OpMemoryBarrier instruction should not be necessary according to the SPIR-V spec for OpControlBarrier.



The commit which introduced the problem is:

    [f2b3e96e754a5d722f2b0fa1bd5efa1c0640ed3b]
    radv: drop copy of ac_create_target_machine.

Looking at the difference between the two implementations, there's the following line in ac_create_target_machine:

    bool barrier_does_waitcnt = family != CHIP_VEGA20;

Changing this to 'false' fixes the problem for me. My GPU is an RX 480 (Polaris 10).



Unfortunately it is quite hard to isolate the exact issue in the game, a renderdoc capture was not useful because the bug got baked into it for some reason, so here's a D3D11 apitrace that needs to be replayed with DXVK in order to reproduce the bug.

https://drive.google.com/file/d/1ywMEhn-P68Sino1_5yBkceLcMACTtDAI/view?usp=sharing