i965/blorp: Reduce the size of vertex buffer

Previously the vertex buffer consisted of eight floats per vertex
of which six where constants. These can be as easily provided by
vertex fetcher as it is capable of filling vertex elements with
constant one and zero. This reduces the size of the vertex buffer
from 3 * 8 * 4 = 96 to 3 * 2 * 4 = 24 bytes.

Signed-off-by: Topi Pohjolainen <topi.pohjolainen@intel.com>
Reviewed-by: Kenneth Graunke <kenneth@whitecape.org>

diff --git a/src/mesa/drivers/dri/i965/gen6_blorp.cpp b/src/mesa/drivers/dri/i965/gen6_blorp.cpp
index b741e19abc49aed2011c9deddfbad9e9bde3cc35..cf30f71ea515304d4d00e90788650ce7ac50dabc 100644 (file)
--- a/src/mesa/drivers/dri/i965/gen6_blorp.cpp
+++ b/src/mesa/drivers/dri/i965/gen6_blorp.cpp
@@ -159,14 +159,21 @@ gen6_blorp_emit_vertices(struct brw_context *brw,
     *
     * For details, see the Sandybridge PRM, Volume 2, Part 1, Section 1.5.1
     * "Vertex URB Entry (VUE) Formats".
+    *
+    * Only vertex position X and Y are going to be variable, Z is fixed to
+    * zero and W to one. Header words dw0-3 are all zero. There is no need to
+    * include the fixed values in the vertex buffer. Vertex fetcher can be
+    * instructed to fill vertex elements with constant values of one and zero
+    * instead of reading them from the buffer. See the vertex element setup
+    * below.
     */
    {
       float *vertex_data;
 
       const float vertices[] = {
-         /* v0 */ 0, 0, 0, 0, (float)params->x0, (float)params->y1, 0, 1,
-         /* v1 */ 0, 0, 0, 0, (float)params->x1, (float)params->y1, 0, 1,
-         /* v2 */ 0, 0, 0, 0, (float)params->x0, (float)params->y0, 0, 1,
+         /* v0 */ (float)params->x0, (float)params->y1,
+         /* v1 */ (float)params->x1, (float)params->y1,
+         /* v2 */ (float)params->x0, (float)params->y0,
       };
 
       vertex_data = (float *) brw_state_batch(brw, AUB_TRACE_VERTEX_BUFFER,
@@ -174,7 +181,7 @@ gen6_blorp_emit_vertices(struct brw_context *brw,
                                               &vertex_offset);
       memcpy(vertex_data, vertices, sizeof(vertices));
 
-      const unsigned blorp_num_vue_elems = 8;
+      const unsigned blorp_num_vue_elems = 2;
       gen6_blorp_emit_vertex_buffer_state(brw, blorp_num_vue_elems,
                                           sizeof(vertices), vertex_offset);
    }
@@ -194,18 +201,18 @@ gen6_blorp_emit_vertices(struct brw_context *brw,
       OUT_BATCH(GEN6_VE0_VALID |
                 BRW_SURFACEFORMAT_R32G32B32A32_FLOAT << BRW_VE0_FORMAT_SHIFT |
                 0 << BRW_VE0_SRC_OFFSET_SHIFT);
-      OUT_BATCH(BRW_VE1_COMPONENT_STORE_SRC << BRW_VE1_COMPONENT_0_SHIFT |
-                BRW_VE1_COMPONENT_STORE_SRC << BRW_VE1_COMPONENT_1_SHIFT |
-                BRW_VE1_COMPONENT_STORE_SRC << BRW_VE1_COMPONENT_2_SHIFT |
-                BRW_VE1_COMPONENT_STORE_SRC << BRW_VE1_COMPONENT_3_SHIFT);
+      OUT_BATCH(BRW_VE1_COMPONENT_STORE_0 << BRW_VE1_COMPONENT_0_SHIFT |
+                BRW_VE1_COMPONENT_STORE_0 << BRW_VE1_COMPONENT_1_SHIFT |
+                BRW_VE1_COMPONENT_STORE_0 << BRW_VE1_COMPONENT_2_SHIFT |
+                BRW_VE1_COMPONENT_STORE_0 << BRW_VE1_COMPONENT_3_SHIFT);
       /* Element 1 */
       OUT_BATCH(GEN6_VE0_VALID |
-                BRW_SURFACEFORMAT_R32G32B32A32_FLOAT << BRW_VE0_FORMAT_SHIFT |
-                16 << BRW_VE0_SRC_OFFSET_SHIFT);
+                BRW_SURFACEFORMAT_R32G32_FLOAT << BRW_VE0_FORMAT_SHIFT |
+                0 << BRW_VE0_SRC_OFFSET_SHIFT);
       OUT_BATCH(BRW_VE1_COMPONENT_STORE_SRC << BRW_VE1_COMPONENT_0_SHIFT |
                 BRW_VE1_COMPONENT_STORE_SRC << BRW_VE1_COMPONENT_1_SHIFT |
-                BRW_VE1_COMPONENT_STORE_SRC << BRW_VE1_COMPONENT_2_SHIFT |
-                BRW_VE1_COMPONENT_STORE_SRC << BRW_VE1_COMPONENT_3_SHIFT);
+                BRW_VE1_COMPONENT_STORE_0 << BRW_VE1_COMPONENT_2_SHIFT |
+                BRW_VE1_COMPONENT_STORE_1_FLT << BRW_VE1_COMPONENT_3_SHIFT);
       ADVANCE_BATCH();
    }
 }