i965/vs: Generalize attribute setup code in preparation for GS.

This patch introduces a new function,
vec4_visitor::lower_attributes_to_hw_regs(), which replaces registers
of type ATTR in the instruction stream with the hardware registers
that store those attributes.  This logic will need to be common
between the vertex and geometry shaders.

Reviewed-by: Jordan Justen <jordan.l.justen@intel.com>
Reviewed-by: Kenneth Graunke <kenneth@whitecape.org>

src/mesa/drivers/dri/i965/brw_vec4.cpp

@@ -1184,29 +1184,13 @@ vec4_visitor::dump_instructions()
    }
 }
 
-int
-vec4_vs_visitor::setup_attributes(int payload_reg)
+/**
+ * Replace each register of type ATTR in this->instructions with a reference
+ * to a fixed HW register.
+ */
+void
+vec4_visitor::lower_attributes_to_hw_regs(const int *attribute_map)
 {
-   int nr_attributes;
-   int attribute_map[VERT_ATTRIB_MAX + 1];
-
-   nr_attributes = 0;
-   for (int i = 0; i < VERT_ATTRIB_MAX; i++) {
-      if (vs_prog_data->inputs_read & BITFIELD64_BIT(i)) {
-	 attribute_map[i] = payload_reg + nr_attributes;
-	 nr_attributes++;
-      }
-   }
-
-   /* 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.
-    */
-   if (vs_prog_data->uses_vertexid) {
-      attribute_map[VERT_ATTRIB_MAX] = payload_reg + nr_attributes;
-      nr_attributes++;
-   }
-
    foreach_list(node, &this->instructions) {
       vec4_instruction *inst = (vec4_instruction *)node;
 
@@ -1240,6 +1224,32 @@ vec4_vs_visitor::setup_attributes(int payload_reg)
 	 inst->src[i].fixed_hw_reg = reg;
       }
    }
+}
+
+int
+vec4_vs_visitor::setup_attributes(int payload_reg)
+{
+   int nr_attributes;
+   int attribute_map[VERT_ATTRIB_MAX + 1];
+
+   nr_attributes = 0;
+   for (int i = 0; i < VERT_ATTRIB_MAX; i++) {
+      if (vs_prog_data->inputs_read & BITFIELD64_BIT(i)) {
+	 attribute_map[i] = payload_reg + nr_attributes;
+	 nr_attributes++;
+      }
+   }
+
+   /* 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.
+    */
+   if (vs_prog_data->uses_vertexid) {
+      attribute_map[VERT_ATTRIB_MAX] = payload_reg + nr_attributes;
+      nr_attributes++;
+   }
+
+   lower_attributes_to_hw_regs(attribute_map);
 
    /* The BSpec says we always have to read at least one thing from
     * the VF, and it appears that the hardware wedges otherwise.

src/mesa/drivers/dri/i965/brw_vec4.h

@@ -480,6 +480,7 @@ public:
 
 protected:
    void emit_vertex();
+   void lower_attributes_to_hw_regs(const int *attribute_map);
    virtual dst_reg *make_reg_for_system_value(ir_variable *ir) = 0;
    virtual int setup_attributes(int payload_reg) = 0;
    virtual void emit_prolog() = 0;