add position to instruction (for relative calculations)

lib/register/assembler.rb

@@ -29,6 +29,7 @@ module Register
       @objects.each do |id , slot|
         next unless slot.object.is_a? Virtual::CompiledMethod
         slot.position = at
+        slot.object.set_position at
         at += slot.length
       end
       @objects.each do |id , slot|

lib/register/instruction.rb

@@ -17,6 +17,7 @@ module Register
       @attributes = options
     end
     attr_reader :attributes
+    attr_accessor :position
     def opcode
       @attributes[:opcode]
     end