Created attachment 141686 [details]
potentially the buggy shader

Here is a shader that may be the buggy one ?

Thanks with iive who was running a trace on his side (r600 doesn't have the
bug), we identified a drawcall where the engine would appear on his side and
not mine (radeonsi).

The draw calls has alpha test disabled, but has stencil test enabled.
I used monolithic shader to ease reading.

It may be a false alarms, as the conditions of the test cannot guarantee this
is really the first moment the two cards have a difference in their rendering
(which may affect the stencil test for example).