i965: Add support for gl_VertexID and gl_InstanceID.

The compiler setup for these VF-uploaded attributes looks a little
cheesy with mixing system values and real VBO-sourced attributes.  It
would be nice if we could just compute the ATTR[] map to GRF index up
front and use it at visit time instead of using ir->location in the
ATTR file.  However, we don't know the reg_offset at
visit(ir_variable *) time, so we can't do the mapping that early.

Fixes piglit vertexid test.

Reviewed-by: Ian Romanick <[email protected]>

1 files changed, 21 insertions, 0 deletions

diff --git a/src/mesa/drivers/dri/i965/brw_vec4_visitor.cpp b/src/mesa/drivers/dri/i965/brw_vec4_visitor.cpp
index 5b80f559015..853c3eeca13 100644
--- a/src/mesa/drivers/dri/i965/brw_vec4_visitor.cpp
+++ b/src/mesa/drivers/dri/i965/brw_vec4_visitor.cpp
@@ -880,6 +880,27 @@ vec4_visitor::visit(ir_variable *ir)
       }
       break;
 
+   case ir_var_system_value:
+      /* VertexID is stored by the VF as the last vertex element, but
+       * we don't represent it with a flag in inputs_read, so we call
+       * it VERT_ATTRIB_MAX, which setup_attributes() picks up on.
+       */
+      reg = new(mem_ctx) dst_reg(ATTR, VERT_ATTRIB_MAX);
+      prog_data->uses_vertexid = true;
+
+      switch (ir->location) {
+      case SYSTEM_VALUE_VERTEX_ID:
+	 reg->writemask = WRITEMASK_X;
+	 break;
+      case SYSTEM_VALUE_INSTANCE_ID:
+	 reg->writemask = WRITEMASK_Y;
+	 break;
+      default:
+	 assert(!"not reached");
+	 break;
+      }
+      break;
+
    default:
       assert(!"not reached");
    }