i965: Make gl_BaseVertex available in a buffer object.

This will be used for GL_ARB_shader_draw_parameters, as well as fixing
gl_VertexID, which is supposed to include gl_BaseVertex's value.

For indirect draws, we simply point at the indirect buffer; for normal
draws, we upload the value via the upload buffer.

Signed-off-by: Kenneth Graunke <[email protected]>
Reviewed-by: Ian Romanick <[email protected]>

3 files changed, 31 insertions, 0 deletions

diff --git a/src/mesa/drivers/dri/i965/brw_context.h b/src/mesa/drivers/dri/i965/brw_context.h
index 25b3298235a..39cb8566b63 100644
--- a/src/mesa/drivers/dri/i965/brw_context.h
+++ b/src/mesa/drivers/dri/i965/brw_context.h
@@ -1067,6 +1067,13 @@ struct brw_context
 
       int start_vertex_location;
       int base_vertex_location;
+
+      /**
+       * Buffer and offset used for GL_ARB_shader_draw_parameters
+       * (for now, only gl_BaseVertex).
+       */
+      drm_intel_bo *draw_params_bo;
+      uint32_t draw_params_offset;
    } draw;
 
    struct {
diff --git a/src/mesa/drivers/dri/i965/brw_draw.c b/src/mesa/drivers/dri/i965/brw_draw.c
index c2866d0dacc..efa85dec540 100644
--- a/src/mesa/drivers/dri/i965/brw_draw.c
+++ b/src/mesa/drivers/dri/i965/brw_draw.c
@@ -434,6 +434,20 @@ static bool brw_try_draw_prims( struct gl_context *ctx,
       brw->draw.start_vertex_location = prims[i].start;
       brw->draw.base_vertex_location = prims[i].basevertex;
 
+      if (prims[i].is_indirect) {
+         /* Point draw_params_bo at the indirect buffer. */
+         brw->draw.draw_params_bo =
+            intel_buffer_object(ctx->DrawIndirectBuffer)->buffer;
+         brw->draw.draw_params_offset =
+            prims[i].indirect_offset + (prims[i].indexed ? 12 : 8);
+      } else {
+         /* Set draw_params_bo to NULL so brw_prepare_vertices knows it
+          * has to upload gl_BaseVertex and such if they're needed.
+          */
+         brw->draw.draw_params_bo = NULL;
+         brw->draw.draw_params_offset = 0;
+      }
+
       if (brw->gen < 6)
 	 brw_set_prim(brw, &prims[i]);
       else
diff --git a/src/mesa/drivers/dri/i965/brw_draw_upload.c b/src/mesa/drivers/dri/i965/brw_draw_upload.c
index 38b108751ce..37a65bcb3c9 100644
--- a/src/mesa/drivers/dri/i965/brw_draw_upload.c
+++ b/src/mesa/drivers/dri/i965/brw_draw_upload.c
@@ -607,11 +607,21 @@ brw_prepare_vertices(struct brw_context *brw)
 void
 brw_prepare_shader_draw_parameters(struct brw_context *brw)
 {
+   int *gl_basevertex_value;
    if (brw->draw.indexed) {
       brw->draw.start_vertex_location += brw->ib.start_vertex_offset;
       brw->draw.base_vertex_location += brw->vb.start_vertex_bias;
+      gl_basevertex_value = &brw->draw.base_vertex_location;
    } else {
       brw->draw.start_vertex_location += brw->vb.start_vertex_bias;
+      gl_basevertex_value = &brw->draw.start_vertex_location;
+   }
+
+   /* For non-indirect draws, upload gl_BaseVertex. */
+   if (brw->vs.prog_data->uses_vertexid && brw->draw.draw_params_bo == NULL) {
+      intel_upload_data(brw, gl_basevertex_value, 4, 4,
+			&brw->draw.draw_params_bo,
+                        &brw->draw.draw_params_offset);
    }
 }