[Mesa-dev] [PATCH 7/7] i965: Reduce vertex state reemission

[Kristian Høgsberg Kristensen]

We can inspect VS prog_data for iterations i > 0, and only flag
BRW_NEW_VERTICES when one of our system values change.

This change also flags BRW_NEW_VERTICES in one case we were missing
before: if we're doing an indirect draw, prims[i].basevertex is always 0
and the real base vertex value is in the indirect parameter
buffer. Thus, if a program uses base vertex or base instance, and the
draw call is indirect, flag BRW_NEW_VERTICES.  A new piglit test,
spec/ARB_shader_draw_parameters/drawid-indirect-vertexid tests this.
---
 src/mesa/drivers/dri/i965/brw_draw.c | 44 ++++++++++++++++++++++++++++++++----
 1 file changed, 40 insertions(+), 4 deletions(-)

diff --git a/src/mesa/drivers/dri/i965/brw_draw.c b/src/mesa/drivers/dri/i965/brw_draw.c
index b0710c67..9e400ca 100644
--- a/src/mesa/drivers/dri/i965/brw_draw.c
+++ b/src/mesa/drivers/dri/i965/brw_draw.c
@@ -491,9 +491,44 @@ brw_try_draw_prims(struct gl_context *ctx,
          }
       }
 
-      brw->draw.params.gl_basevertex =
+      /* Determine if we need to flag BRW_NEW_VERTICES for updating the
+       * gl_BaseVertexARB, gl_BaseInstanceARB or gl_DrawIDARB values. As
+       * above, we don't need to check first iteration, since the flag is set
+       * before the loop. We also can't rely on vs prog_data in the first
+       * iteration, but after drawing once, we've uploaded the programs and
+       * can look at prog_data.
+       *
+       * Despite the prims[] name, eache iteration correspond to a draw call
+       * from a glMulti* style draw call. We need to re-upload vertex state if
+       *
+       *  1) the program uses gl_DrawIDARB (changes every iteration),
+       *
+       *  2) the program uses gl_BaseVertexARB or gl_BaseInstanceARB and the
+       *     draw call is indirect (meaning we can't check if the value change
+       *     or not), or
+       *
+       *  3) the program uses gl_BaseVertexARB or gl_BaseInstanceARB and the
+       *  value changed
+       */
+      const int new_basevertex =
          prims[i].indexed ? prims[i].basevertex : prims[i].start;
-      brw->draw.params.gl_baseinstance = prims[i].base_instance;
+      const int new_baseinstance = prims[i].base_instance;
+      if (i > 0) {
+         const bool uses_draw_parameters =
+            brw->vs.prog_data->uses_basevertex ||
+            brw->vs.prog_data->uses_baseinstance;
+
+         if (brw->vs.prog_data->uses_drawid ||
+             (uses_draw_parameters && prims[i].is_indirect) ||
+             (brw->vs.prog_data->uses_basevertex &&
+              brw->draw.params.gl_basevertex != new_basevertex) ||
+             (brw->vs.prog_data->uses_baseinstance &&
+              brw->draw.params.gl_baseinstance != new_baseinstance))
+            brw->ctx.NewDriverState |= BRW_NEW_VERTICES;
+      }
+
+      brw->draw.params.gl_basevertex = new_basevertex;
+      brw->draw.params.gl_baseinstance = new_baseinstance;
       drm_intel_bo_unreference(brw->draw.draw_params_bo);
 
       if (prims[i].is_indirect) {
@@ -512,10 +547,11 @@ brw_try_draw_prims(struct gl_context *ctx,
       }
 
       /* gl_DrawID always needs its own vertex buffer since it's not part of
-       * the indirect parameter buffer. */
+       * the indirect parameter buffer.
+       */
       brw->draw.gl_drawid = prims[i].draw_id;
       drm_intel_bo_unreference(brw->draw.draw_id_bo);
-      brw->ctx.NewDriverState |= BRW_NEW_VERTICES;
+      brw->draw.draw_id_bo = NULL;
 
       if (brw->gen < 6)
 	 brw_set_prim(brw, &prims[i]);
-- 
2.5.0