Fix non ssa issue

register instances were being shared across instructions
causing the setting to have side-effects
Fixed this by copying the register on write
(fixing the symptom rather than the cause, i'll make an issue)

test/risc/test_register_value.rb

@@ -24,6 +24,11 @@ module Risc
     def test_r0
       assert_equal :message , @r0.symbol
     end
+    def test_dup
+      copy = @r0.dup( :r0 )
+      assert_equal :r0 , copy.symbol
+      assert_equal :message , copy.ssa
+    end
     def test_load_label
       label = Risc::Label.new("HI","ho" , FakeAddress.new(0))
       move = @r1 << label

test/risc/test_register_value1.rb

@@ -53,12 +53,5 @@ module Risc
     def test_has_ssa
       assert_nil @r0.ssa
     end
-    def test_set_name
-      assert_equal :message , @r0.set_name(:r0)
-    end
-    def test_set_ssa
-      @r0.set_name(:r0)
-      assert_equal :message , @r0.ssa
-    end
   end
 end

test/risc/test_standard_allocator1.rb

@@ -13,7 +13,7 @@ module Risc
     end
     def test_allocate_runs
       assert_nil @allocator.allocate_regs
-      #assert_equal 0 , @allocator.used_regs.length
+      assert_equal 0 , @allocator.used_regs.length
     end
     def test_live_length
       live = @allocator.walk_and_mark(@compiler.risc_instructions)