Created attachment 120280 [details]
Before a buggy draw call
I noticed a few games had some strange artifacts on my tonga that I had not on
verde. Those artifacts are usually along lines.
These artifacts disappear with R600_DEBUG=nodcc.
I managed to determine the bug appears when the render target is also used as
input texture.
Attached is the render target content before and after such draw call. The draw
call draws two triangles. We can see the artifacts are along the border region
of the top right triangle with the bottom left triangle.
My guess is that it is some flush issue. That the bottom left triangle is drawn
first, the cache content of the texture cache updated, and the artifacts are at
locations where the dcc data was updated.