Added def-use chain to the intermediate language.

runtime/vm/intermediate_language_test.cc

 // Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 #include "vm/intermediate_language.h"
 #include "vm/unit_test.h"
 
 namespace dart {
 
 TEST_CASE(InstructionTests) {
   TargetEntryInstr* target_instr = new TargetEntryInstr();
   EXPECT(target_instr->IsBlockEntry());
   EXPECT(!target_instr->IsBind());
   BindInstr* bind_instr =
       new BindInstr(BindInstr::kUnused, new CurrentContextComp());
   EXPECT(bind_instr->IsBind());
   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