ir_variable: Add query to get number of slots used by a variable

ir.cpp

@@ -756,6 +756,14 @@ ir_variable::interpolation_string() const
 }
 
 
+unsigned
+ir_variable::component_slots() const
+{
+   /* FINISHME: Sparsely accessed arrays require fewer slots. */
+   return this->type->component_slots();
+}
+
+
 ir_function_signature::ir_function_signature(const glsl_type *return_type)
    : return_type(return_type), is_defined(false)
 {

ir.h

@@ -187,6 +187,14 @@ public:
     */
    const char *interpolation_string() const;
 
+   /**
+    * Calculate the number of slots required to hold this variable
+    *
+    * This is used to determine how many uniform or varying locations a variable
+    * occupies.  The count is in units of floating point components.
+    */
+   unsigned component_slots() const;
+
    const char *name;
 
    /**