[Mesa-dev] [PATCH] i965/skl: Emit new 3DSTATE_VF_COMPONENT_PACKING

[Ben Widawsky]

We don't yet have a use for this state, but initializing it to known values is
always considered wise. In general NULL state can probably go in the misc state
upload, I only put it here because I assume it might be useful at some point.

Signed-off-by: Ben Widawsky <ben at bwidawsk.net>
---

I've had this patch sitting around for almost 3 months now. I believe we like to
initialize new fields as a general rule of thumb.

---
 src/mesa/drivers/dri/i965/brw_defines.h      |  2 ++
 src/mesa/drivers/dri/i965/gen8_draw_upload.c | 29 ++++++++++++++++++++++++++++
 2 files changed, 31 insertions(+)

diff --git a/src/mesa/drivers/dri/i965/brw_defines.h b/src/mesa/drivers/dri/i965/brw_defines.h
index 66b9abc..444d974 100644
--- a/src/mesa/drivers/dri/i965/brw_defines.h
+++ b/src/mesa/drivers/dri/i965/brw_defines.h
@@ -1713,6 +1713,8 @@ enum brw_message_target {
 
 #define _3DSTATE_VF_TOPOLOGY                    0x784b /* GEN8+ */
 
+#define _3DSTATE_VF_COMPONENT_PACKING           0x7855 /* GEN9+ */
+
 #define _3DSTATE_WM_CHROMAKEY			0x784c /* GEN8+ */
 
 #define _3DSTATE_URB_VS                         0x7830 /* GEN7+ */
diff --git a/src/mesa/drivers/dri/i965/gen8_draw_upload.c b/src/mesa/drivers/dri/i965/gen8_draw_upload.c
index 1af90ec..f6e7fc8 100644
--- a/src/mesa/drivers/dri/i965/gen8_draw_upload.c
+++ b/src/mesa/drivers/dri/i965/gen8_draw_upload.c
@@ -35,6 +35,33 @@
 #include "intel_batchbuffer.h"
 #include "intel_buffer_objects.h"
 
+/**
+ * Emits a null component packing state.
+ *
+ * Paraphrasing the docs: "This command is used to specify which 32-bit
+ * components are "enabled" to be stored in the URB, and which are "disabled".
+ * Disabling all four components for a given Vertex Element will result in no
+ * data stored for that element. Note that any insertion of SGVs
+ * (3DSTATE_VF_SGVS) is performed before the packing operation."
+ *
+ * FINISHME: "Component packing is probably only useful for SIMD8 VS thread
+ * execution." When enabled, the correct bit must be set in 3DSTATE_VF.
+ */
+static void
+gen9_emit_component_packing(struct brw_context *brw)
+{
+   if (brw->gen < 9)
+      return;
+
+   BEGIN_BATCH(5);
+   OUT_BATCH(_3DSTATE_VF_COMPONENT_PACKING << 16 | (5 - 2));
+   OUT_BATCH(0);
+   OUT_BATCH(0);
+   OUT_BATCH(0);
+   OUT_BATCH(0);
+   ADVANCE_BATCH();
+}
+
 static void
 gen8_emit_vertices(struct brw_context *brw)
 {
@@ -44,6 +71,8 @@ gen8_emit_vertices(struct brw_context *brw)
    brw_prepare_vertices(brw);
    brw_prepare_shader_draw_parameters(brw);
 
+   gen9_emit_component_packing(brw);
+
    if (brw->vs.prog_data->uses_vertexid || brw->vs.prog_data->uses_instanceid) {
       unsigned vue = brw->vb.nr_enabled;
 
-- 
2.4.4