[Bug 108820] [SKL] (recoverable) GPU hangs in benchmarks using compute shaders with drm-tip v4.20-rc kernels

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=108820

--- Comment #23 from Jakub Okoński <jakub at okonski.org> ---
I'm trying to reduce the shader to bare-minimum that reproduces the hang, here
it is:

```
#version 450

layout (local_size_x = 65) in;

void main() {
   if (gl_GlobalInvocationID.x >= 20) {
       return;
   }

   barrier();
}
```

New piece of information is the early-return that is required to trigger the
hang. From this baseline shader, if I decrease local_size_x to 64, it works. Or
I can remove the if statement and it will also work. Or I can remove the
barrier() and it will also start to work. It seems to be a combination of these
that causes the hang. If I take away any piece from it, the problem goes away.

I'm attaching the debug info on this minimal shader.

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