Added def-use chain to the intermediate language.

runtime/vm/intermediate_language_test.cc

Index: runtime/vm/intermediate_language_test.cc
diff --git a/runtime/vm/intermediate_language_test.cc b/runtime/vm/intermediate_language_test.cc
index f6b5b870e2ce10a92ddafb71a013f2daa9882125..265db23e3885a9fa51beb92e68334fa02d6ddaef 100644
--- a/runtime/vm/intermediate_language_test.cc
+++ b/runtime/vm/intermediate_language_test.cc
@@ -17,4 +17,28 @@ TEST_CASE(InstructionTests) {
   EXPECT(!bind_instr->IsBlockEntry());
 }
 
+TEST_CASE(DefUseTests) {
+  Definition* def1 = new PhiInstr(0);
+  Definition* def2 = new PhiInstr(0);
+  EXPECT(def1->def_use_chain() == NULL);
+  EXPECT(def2->def_use_chain() == NULL);
+  UseVal* use1 = new UseVal(def1);
+  EXPECT(def1->def_use_chain() == use1);
+  EXPECT(def1->def_use_chain()->next_use() == NULL);
+  UseVal* use2 = new UseVal(def1);
+  EXPECT(def1->def_use_chain()->next_use()->next_use() == NULL);
+  UseVal* use3 = new UseVal(def1);
+  EXPECT(def1->def_use_chain()->next_use()->next_use()->next_use() == NULL);
+  use1->RemoveFromDefUseChain();
+  EXPECT(def1->def_use_chain()->next_use()->next_use() == NULL);
+  use3->set_definition(def2);
+  EXPECT(def1->def_use_chain() == use2);
+  EXPECT(def1->def_use_chain()->next_use() == NULL);
+  EXPECT(def2->def_use_chain() == use3);
+  EXPECT(def2->def_use_chain()->next_use() == NULL);
+  BindInstr* bind = new BindInstr(BindInstr::kUsed, use2);
+  bind->RemoveFromDefUseChain();
+  EXPECT(def1->def_use_chain() == NULL);
+}
+
 }  // namespace dart