Linux. Iris. Gputest gimark has unwanted black liquorice flakes

[DenKos363]

Hello folks. Recently we investigated issue with gimark test on iris driver and found out some image corruptions.
During researching it was found out, that the problem might be in gimark benchmark, not in driver. Could you please check out the issue https://gitlab.freedesktop.org/mesa/mesa/issues/1919 and participate/help with sorting it out?

Thank you in advance! 

[JeGX]

Thanks for the feedback. I will try to do some tests asap (the vec4 lightDir0/1 that are not properly initialized) to confirm if it's a bug or not.

[JeGX]

The GpuTest project is a bit stopped so I can't update it easily. But GpuTest successor will be released shortly 

I can confirm you the bug is from GpuTest. I reproduced it with GeeXLab.  The bug comes from the two vec4 variables that are not initialized in the vertex shader and used in a division in the pixel shader. I tested on Linux Mint 19.2 + Intel UHD 630.

If you want to see the demo in action, download GeeXLab for Linux here:
- https://www.geeks3d.com/dl/show/502

Download the OpenGL 2.1 demopack here:
- https://www.geeks3d.com/dl/show/50100

The demo is in the d07-meshes-bug-intel-gpu-linux-mesa/ folder. Launch GeeXLab and drag and drop the demo main.xml.

You should see something like this:


Now edit the vertex shader: d07-meshes-bug-intel-gpu-linux-mesa/shaders/tex_vs.txt

Comment the line 25 and remove the comment line 28:

Code Select Expand


// Bug on Linux with Intel GPUs + Mesa drivers
//v_lightdir.xyz = LP.xyz - view_vertex.xyz;

// BugFix.
v_lightdir = LP - view_vertex;


You should see:



The un-initialized vec4 bug seems to be visible only on Intel Mesa driver. I tested and the bug is not visible on the following systems:
- Windows 10 + GeForce 444.20 + RTX 2070
- Windows 10 + Intel driver v7463 + UHD 630
- Raspberry Pi 4 + latest raspbian + Mesa 19.2.0 rc1 

I hope that helps!

[DenKos363]

Thank you very much for fast respond. Based on your explanations we prepared and merged patch with workaround of this problem https://gitlab.freedesktop.org/mesa/mesa/merge_requests/2859