i965: Add support for gl_DrawIDARB and enable extension

We have to break open a new vec4 for gl_DrawIDARB. We've used up all
space in the vec4 we use for SGVS and gl_DrawIDARB has to come from its
own separate vertex buffer anyway.  This is because we point the vb for
base vertex and base instance into the draw parameter BO for indirect
draw calls, but the draw id is generated by mesa in a different buffer.

Reviewed-by: Anuj Phogat <anuj.phogat@gmail.com>

1 files changed, 12 insertions, 0 deletions

diff --git a/src/mesa/drivers/dri/i965/brw_draw.c b/src/mesa/drivers/dri/i965/brw_draw.c
index e0665d3..b0a162a 100644
--- a/src/mesa/drivers/dri/i965/brw_draw.c
+++ b/src/mesa/drivers/dri/i965/brw_draw.c
@@ -511,6 +511,18 @@ brw_try_draw_prims(struct gl_context *ctx,
          brw->draw.draw_params_offset = 0;
       }
 
+      /* gl_DrawID always needs its own vertex buffer since it's not part of
+       * the indirect parameter buffer. If the program uses gl_DrawID we need
+       * to flag BRW_NEW_VERTICES. For the first iteration, we don't have
+       * valid brw->vs.prog_data, but we always flag BRW_NEW_VERTICES before
+       * the loop.
+       */
+      brw->draw.gl_drawid = prims[i].draw_id;
+      drm_intel_bo_unreference(brw->draw.draw_id_bo);
+      brw->draw.draw_id_bo = NULL;
+      if (i > 0 && brw->vs.prog_data->uses_drawid)
+         brw->ctx.NewDriverState |= BRW_NEW_VERTICES;
+
       if (brw->gen < 6)
 	 brw_set_prim(brw, &prims[i]);
       else