On 16 December 2011 19:53, Kenneth Graunke <<a href="mailto:kenneth@whitecape.org">kenneth@whitecape.org</a>> wrote: <div class="gmail_quote"><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"> <div class="im">On 12/14/2011 11:59 AM, Paul Berry wrote: > This patch enables rasterizer discard functionality (a part of > transform feedback) in Gen6, by generating an alternate GS program > when rasterizer discard is active. Instead of forwarding vertices > down the pipeline, the alternate GS program uses a URB Write message > to deallocate the URB entry that was allocated by FF sync and > terminate the thread. > > Note: parts of the Sandy Bridge PRM seem to imply that we could do > this more efficiently, by clearing the GEN6_GS_RENDERING_ENABLE bit, > and not allocating a URB entry at all. However, it's not clear how we > are supposed to terminate the thread if we do that. Volume 2 part 1, > section 4.5.4, says "GS threads must terminate by sending a URB_WRITE > message with the EOT and Complete bits set.", and my experiments so > far confirm that. > --- > > This patch needs to be applied on top of the series "[PATCH 0/8] i965 > gen6: Initial implementation of transform feedback.", which is still > under review on the mailing list. </div>Assuming the dirty bit gets sorted out, Reviewed-by: Kenneth Graunke <<a href="mailto:kenneth@whitecape.org">kenneth@whitecape.org</a>> </blockquote></div> Thanks, Ken. Fortunately, this patch is independent of the dirty bit stuff (since this patch adds a use of ctx->TransformFeedback.RasterDiscard to brw_gs_prog, which already depends on _NEW_TRANSFORM). So I'll push it as soon as the remaining discussion on my main transform feedback series is resolved.