start to move slot_load code to register_value

the iea is to iterate through register_values while reducing the slot_load to a number of Slot_to_regs
wip

test/risc/test_register_value.rb

@@ -0,0 +1,59 @@
+require_relative "../helper"
+
+class FakeBuilder
+  attr_reader :built
+  def add_code(ins)
+    @built = ins
+  end
+end
+module Risc
+  class TestRegisterValue < MiniTest::Test
+
+    def setup
+      Parfait.boot!
+      @r0 = RegisterValue.new(:r0 , :Message)
+      @r1 = RegisterValue.new(:r1 , :Space)
+    end
+    def test_r0
+      assert_equal :r0 , @r0.symbol
+    end
+    def test_load_space
+      move = @r0 << Parfait.object_space
+      assert_equal LoadConstant , move.class
+    end
+    def test_load_symbol
+      move = @r1 << :puts
+      assert_equal LoadConstant , move.class
+    end
+    def test_transfer
+      transfer = @r0 << @r1
+      assert_equal Transfer , transfer.class
+    end
+    def test_calls_builder
+      builder = FakeBuilder.new
+      @r0.builder = builder
+      @r0 << @r1
+      assert_equal Transfer , builder.built.class
+    end
+    def test_index_op
+      message = @r0[:next_message]
+      assert_equal RValue , message.class
+      assert_equal :next_message , message.index
+      assert_equal @r0 , message.register
+    end
+    def test_slot_to_reg
+      instr = @r0 << @r1[:next_message]
+      assert_equal SlotToReg , instr.class
+      assert_equal @r1 , instr.array
+      assert_equal @r0 , instr.register
+      assert_equal 3 , instr.index
+    end
+    def test_reg_to_slot
+      instr = @r1[:next_message] << @r0
+      assert_equal RegToSlot , instr.class
+      assert_equal @r1 , instr.array
+      assert_equal @r0 , instr.register
+      assert_equal 3 , instr.index
+    end
+  end
+end