Would you make and upload an apitrace of the game demonstrating the issue?

There is an ftp for traces of Gallium Nine, you can ask in Freenode #d3d9
channel for the password, or simply use google drive or other better file
sharing.
The trace might be kept for future regression testing. (Unless you explicitly
oppose.)

It would be nice if you also open issue at github ixit.Mesa-3D, where most of
Gallium Nine bugs are tracked.
Since the bug itself is outside of Nine, it is good that you have it filled
here.

BTW, since the bug is regression and you've located it, be sure to put the
regression and bisected tags/keywords. I just added them. It help developers if
they know that the mundane and time consuming work has already been done. (I
hope.)