Added def-use chain to the intermediate language.

runtime/vm/intermediate_language.cc

Index: runtime/vm/intermediate_language.cc
diff --git a/runtime/vm/intermediate_language.cc b/runtime/vm/intermediate_language.cc
index 3a1c8c54eef914a2c09fabe76006286fa6357a12..aab31326e6955b50be39bc87d61539ba2530c1f4 100644
--- a/runtime/vm/intermediate_language.cc
+++ b/runtime/vm/intermediate_language.cc
@@ -20,6 +20,45 @@ namespace dart {
 
 DECLARE_FLAG(bool, enable_type_checks);
 
+UseVal::UseVal(Definition* definition)
+    : definition_(definition), next_use_(NULL), previous_use_(NULL) {
+  AddToDefUseChain();
+}
+
+void UseVal::set_definition(Definition* definition) {
+  ASSERT(definition != NULL);
+  RemoveFromDefUseChain();
+  definition_ = definition;
+  AddToDefUseChain();
+}
+
+void UseVal::RemoveFromDefUseChain() {
+  ASSERT(definition_ != NULL);
+  if (previous_use_ == NULL) {
+    ASSERT(definition_->def_use_chain() == this);
+    definition_->set_def_use_chain(next_use_);
+  } else {
+    previous_use_->next_use_ = next_use_;
+  }
+  if (next_use_ != NULL) {
+    next_use_->previous_use_ = previous_use_;
+  }
+  previous_use_ = next_use_ = NULL;
+  definition_ = NULL;
+}
+
+void UseVal::AddToDefUseChain() {
+  ASSERT(next_use_ == NULL && previous_use_ == NULL && definition_ != NULL);
+  UseVal* chain = definition_->def_use_chain();
+  if (chain != NULL) {
+    next_use_ = chain;
+    chain->previous_use_ = this;
+  }
+  definition_->set_def_use_chain(this);
+}
+
+
+
 
 MethodRecognizer::Kind MethodRecognizer::RecognizeKind(
     const Function& function) {