i965 Fragment Issues with Kernel 5.10
I am running into an issue where certain fragments flicker and are discarded related to the orientation of the camera and other vague conditions. This issue occurs with the terrain in my game with kernel 5.10, but not with kernel 5.8. The sky does seem to have flickering pixels at times with both kernels, but I am not sure if that is related.
I have tested with both Mesa 18.3.6 and 20.3.4 on an Intel HD 4000 (Debian Testing). This does not occur on another system with an AMD gpu driver on Mesa 18.3.6 / kernel 4.19 (Debian Stable). The shader code is fairly complex with double emulation on the GPU side, and so I am not completely sure that it might not be related to that. But I have not previously seen this issue on several configurations.
I have included the apitrace. The issue should appear in the terrain on kernel 5.10, but not kernel 5.8. This is most noticeable right at the end of the trace. Please be patient at the beginning of the trace as I have funky exposure compensation code that will overexpose everything for a few seconds. The problem is most likely to occur at triangle boundaries, but I have observed it all over. It also is much more likely with tessellated geometry.