i965: Add support for gl_DrawIDARB and enable extension

We have to break open a new vec4 for gl_DrawIDARB. We've used up all
space in the vec4 we use for SGVS and gl_DrawIDARB has to come from its
own separate vertex buffer anyway.  This is because we point the vb for
base vertex and base instance into the draw parameter BO for indirect
draw calls, but the draw id is generated by mesa in a different buffer.

Reviewed-by: Anuj Phogat <anuj.phogat@gmail.com>

1 files changed, 10 insertions, 0 deletions

diff --git a/src/mesa/drivers/dri/i965/brw_fs_visitor.cpp b/src/mesa/drivers/dri/i965/brw_fs_visitor.cpp
index d6941fa..25240ad 100644
--- a/src/mesa/drivers/dri/i965/brw_fs_visitor.cpp
+++ b/src/mesa/drivers/dri/i965/brw_fs_visitor.cpp
@@ -59,6 +59,16 @@ fs_visitor::emit_vs_system_value(int location)
       reg->reg_offset = 3;
       vs_prog_data->uses_instanceid = true;
       break;
+   case SYSTEM_VALUE_DRAW_ID:
+      if (nir->info.system_values_read &
+          (BITFIELD64_BIT(SYSTEM_VALUE_BASE_VERTEX) |
+           BITFIELD64_BIT(SYSTEM_VALUE_BASE_INSTANCE) |
+           BITFIELD64_BIT(SYSTEM_VALUE_VERTEX_ID_ZERO_BASE) |
+           BITFIELD64_BIT(SYSTEM_VALUE_INSTANCE_ID)))
+         reg->nr += 4;
+      reg->reg_offset = 0;
+      vs_prog_data->uses_drawid = true;
+      break;
    default:
       unreachable("not reached");
    }