Mesa (master): anv: only expose up to 28 vertex attributes

[Iago Toral Quiroga]

Module: Mesa
Branch: master
Commit: 31f1863ace73d31a579e5c36252a957818ad09cf
URL:    http://cgit.freedesktop.org/mesa/mesa/commit/?id=31f1863ace73d31a579e5c36252a957818ad09cf

Author: Iago Toral Quiroga <itoral at igalia.com>
Date:   Fri Jul 21 08:32:24 2017 +0200

anv: only expose up to 28 vertex attributes

The EU limit of 128 GRFs should allow 32 vertex elements of 4 GRFs.
However, the maximum allowed value of "Vertex URB Entry Read Length"
in SIMD8 is 15. And 15 * 8 = 120 gives us a limit of 30 vertex elements.
Because we also need to reserve a vertex buffer to upload
VertexIndex/InstanceIndex and another to upload DrawID when needed,
we can only expose 28.

Cc: "17.2" <mesa-stable at lists.freedesktop.org>
Reviewed-by: Lionel Landwerlin <lionel.g.landwerlin at intel.com>

---

 src/intel/vulkan/anv_private.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/intel/vulkan/anv_private.h b/src/intel/vulkan/anv_private.h
index faf7849891..86c430397c 100644
--- a/src/intel/vulkan/anv_private.h
+++ b/src/intel/vulkan/anv_private.h
@@ -89,7 +89,7 @@ struct gen_l3_config;
  */
 #define ANV_HZ_FC_VAL 1.0f
 
-#define MAX_VBS         31
+#define MAX_VBS         28
 #define MAX_SETS         8
 #define MAX_RTS          8
 #define MAX_VIEWPORTS   16