1 files changed, 30 insertions, 26 deletions

diff --git a/compiler/optimizing/nodes.cc b/compiler/optimizing/nodes.cc
index ec53366e19..fe9ce740da 100644
--- a/compiler/optimizing/nodes.cc
+++ b/compiler/optimizing/nodes.cc
@@ -39,9 +39,11 @@ static void RemoveAsUser(HInstruction* instruction) {
   HEnvironment* environment = instruction->GetEnvironment();
   if (environment != nullptr) {
     for (size_t i = 0, e = environment->Size(); i < e; ++i) {
-      HInstruction* vreg = environment->GetInstructionAt(i);
-      if (vreg != nullptr) {
-        vreg->RemoveEnvironmentUser(environment, i);
+      HUseListNode<HEnvironment*>* vreg_env_use = environment->GetInstructionEnvUseAt(i);
+      if (vreg_env_use != nullptr) {
+        HInstruction* vreg = environment->GetInstructionAt(i);
+        DCHECK(vreg != nullptr);
+        vreg->RemoveEnvironmentUser(vreg_env_use);
       }
     }
   }
@@ -425,8 +427,8 @@ static void Remove(HInstructionList* instruction_list,
                    HBasicBlock* block,
                    HInstruction* instruction) {
   DCHECK_EQ(block, instruction->GetBlock());
-  DCHECK(instruction->GetUses() == nullptr);
-  DCHECK(instruction->GetEnvUses() == nullptr);
+  DCHECK(instruction->GetUses().IsEmpty());
+  DCHECK(instruction->GetEnvUses().IsEmpty());
   instruction->SetBlock(nullptr);
   instruction_list->RemoveInstruction(instruction);
 
@@ -441,22 +443,24 @@ void HBasicBlock::RemovePhi(HPhi* phi) {
   Remove(&phis_, this, phi);
 }
 
+void HEnvironment::CopyFrom(HEnvironment* env) {
+  for (size_t i = 0; i < env->Size(); i++) {
+    HInstruction* instruction = env->GetInstructionAt(i);
+    SetRawEnvAt(i, instruction);
+    if (instruction != nullptr) {
+      instruction->AddEnvUseAt(this, i);
+    }
+  }
+}
+
 template <typename T>
-static void RemoveFromUseList(T* user,
-                              size_t input_index,
-                              HUseListNode<T>** list) {
-  HUseListNode<T>* previous = nullptr;
-  HUseListNode<T>* current = *list;
-  while (current != nullptr) {
+static void RemoveFromUseList(T user, size_t input_index, HUseList<T>* list) {
+  HUseListNode<T>* current;
+  for (HUseIterator<HInstruction*> use_it(*list); !use_it.Done(); use_it.Advance()) {
+    current = use_it.Current();
     if (current->GetUser() == user && current->GetIndex() == input_index) {
-      if (previous == nullptr) {
-        *list = current->GetTail();
-      } else {
-        previous->SetTail(current->GetTail());
-      }
+      list->Remove(current);
     }
-    previous = current;
-    current = current->GetTail();
   }
 }
 
@@ -480,8 +484,8 @@ void HInstruction::RemoveUser(HInstruction* user, size_t input_index) {
   RemoveFromUseList(user, input_index, &uses_);
 }
 
-void HInstruction::RemoveEnvironmentUser(HEnvironment* user, size_t input_index) {
-  RemoveFromUseList(user, input_index, &env_uses_);
+void HInstruction::RemoveEnvironmentUser(HUseListNode<HEnvironment*>* use) {
+  env_uses_.Remove(use);
 }
 
 void HInstructionList::AddInstruction(HInstruction* instruction) {
@@ -573,24 +577,24 @@ bool HInstruction::StrictlyDominates(HInstruction* other_instruction) const {
 
 void HInstruction::ReplaceWith(HInstruction* other) {
   DCHECK(other != nullptr);
-  for (HUseIterator<HInstruction> it(GetUses()); !it.Done(); it.Advance()) {
-    HUseListNode<HInstruction>* current = it.Current();
+  for (HUseIterator<HInstruction*> it(GetUses()); !it.Done(); it.Advance()) {
+    HUseListNode<HInstruction*>* current = it.Current();
     HInstruction* user = current->GetUser();
     size_t input_index = current->GetIndex();
     user->SetRawInputAt(input_index, other);
     other->AddUseAt(user, input_index);
   }
 
-  for (HUseIterator<HEnvironment> it(GetEnvUses()); !it.Done(); it.Advance()) {
-    HUseListNode<HEnvironment>* current = it.Current();
+  for (HUseIterator<HEnvironment*> it(GetEnvUses()); !it.Done(); it.Advance()) {
+    HUseListNode<HEnvironment*>* current = it.Current();
     HEnvironment* user = current->GetUser();
     size_t input_index = current->GetIndex();
     user->SetRawEnvAt(input_index, other);
     other->AddEnvUseAt(user, input_index);
   }
 
-  uses_ = nullptr;
-  env_uses_ = nullptr;
+  uses_.Clear();
+  env_uses_.Clear();
 }
 
 void HInstruction::ReplaceInput(HInstruction* replacement, size_t index) {