[turbofan] optimize hot loop in ResolveControlFlow

R=jarin@chromium.org

BUG=

Review URL: https://codereview.chromium.org/694473002

Cr-Commit-Position: refs/heads/master@{#25149}
git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@25149 ce2b1a6d-e550-0410-aec6-3dcde31c8c00

src/compiler/register-allocator.cc

@@ -199,7 +199,7 @@ bool LiveRange::CanBeSpilled(LifetimePosition pos) {
 }
 
 
-InstructionOperand* LiveRange::CreateAssignedOperand(Zone* zone) {
+InstructionOperand* LiveRange::CreateAssignedOperand(Zone* zone) const {
   InstructionOperand* op = NULL;
   if (HasRegisterAssigned()) {
     DCHECK(!IsSpilled());
@@ -507,23 +507,24 @@ LifetimePosition LiveRange::FirstIntersection(LiveRange* other) {
 
 
 RegisterAllocator::RegisterAllocator(const RegisterConfiguration* config,
-                                     Zone* local_zone, Frame* frame,
+                                     Zone* zone, Frame* frame,
                                      InstructionSequence* code,
                                      const char* debug_name)
-    : zone_(local_zone),
+    : local_zone_(zone),
       frame_(frame),
       code_(code),
       debug_name_(debug_name),
       config_(config),
-      live_in_sets_(code->InstructionBlockCount(), zone()),
-      live_ranges_(code->VirtualRegisterCount() * 2, zone()),
-      fixed_live_ranges_(this->config()->num_general_registers(), NULL, zone()),
+      live_in_sets_(code->InstructionBlockCount(), local_zone()),
+      live_ranges_(code->VirtualRegisterCount() * 2, local_zone()),
+      fixed_live_ranges_(this->config()->num_general_registers(), NULL,
+                         local_zone()),
       fixed_double_live_ranges_(this->config()->num_double_registers(), NULL,
-                                zone()),
-      unhandled_live_ranges_(code->VirtualRegisterCount() * 2, zone()),
-      active_live_ranges_(8, zone()),
-      inactive_live_ranges_(8, zone()),
-      reusable_slots_(8, zone()),
+                                local_zone()),
+      unhandled_live_ranges_(code->VirtualRegisterCount() * 2, local_zone()),
+      active_live_ranges_(8, local_zone()),
+      inactive_live_ranges_(8, local_zone()),
+      reusable_slots_(8, local_zone()),
       mode_(UNALLOCATED_REGISTERS),
       num_registers_(-1),
       allocation_ok_(true) {
@@ -541,16 +542,16 @@ RegisterAllocator::RegisterAllocator(const RegisterConfiguration* config,
 void RegisterAllocator::InitializeLivenessAnalysis() {
   // Initialize the live_in sets for each block to NULL.
   int block_count = code()->InstructionBlockCount();
-  live_in_sets_.Initialize(block_count, zone());
-  live_in_sets_.AddBlock(NULL, block_count, zone());
+  live_in_sets_.Initialize(block_count, local_zone());
+  live_in_sets_.AddBlock(NULL, block_count, local_zone());
 }
 
 
 BitVector* RegisterAllocator::ComputeLiveOut(const InstructionBlock* block) {
   // Compute live out for the given block, except not including backward
   // successor edges.
-  BitVector* live_out =
-      new (zone()) BitVector(code()->VirtualRegisterCount(), zone());
+  BitVector* live_out = new (local_zone())
+      BitVector(code()->VirtualRegisterCount(), local_zone());
 
   // Process all successor blocks.
   for (auto succ : block->successors()) {
@@ -584,7 +585,7 @@ void RegisterAllocator::AddInitialIntervals(const InstructionBlock* block,
   while (!iterator.Done()) {
     int operand_index = iterator.Current();
     LiveRange* range = LiveRangeFor(operand_index);
-    range->AddUseInterval(start, end, zone());
+    range->AddUseInterval(start, end, local_zone());
     iterator.Advance();
   }
 }
@@ -630,7 +631,7 @@ LiveRange* RegisterAllocator::FixedLiveRangeFor(int index) {
     // The LiveRange object itself can go in this zone, but the
     // InstructionOperand needs
     // to go in the code zone, since it may survive register allocation.
-    result = new (zone()) LiveRange(FixedLiveRangeID(index), code_zone());
+    result = new (local_zone()) LiveRange(FixedLiveRangeID(index), code_zone());
     DCHECK(result->IsFixed());
     result->kind_ = GENERAL_REGISTERS;
     SetLiveRangeAssignedRegister(result, index);
@@ -644,7 +645,8 @@ LiveRange* RegisterAllocator::FixedDoubleLiveRangeFor(int index) {
   DCHECK(index < config()->num_aliased_double_registers());
   LiveRange* result = fixed_double_live_ranges_[index];
   if (result == NULL) {
-    result = new (zone()) LiveRange(FixedDoubleLiveRangeID(index), code_zone());
+    result = new (local_zone())
+        LiveRange(FixedDoubleLiveRangeID(index), code_zone());
     DCHECK(result->IsFixed());
     result->kind_ = DOUBLE_REGISTERS;
     SetLiveRangeAssignedRegister(result, index);
@@ -656,11 +658,12 @@ LiveRange* RegisterAllocator::FixedDoubleLiveRangeFor(int index) {
 
 LiveRange* RegisterAllocator::LiveRangeFor(int index) {
   if (index >= live_ranges_.length()) {
-    live_ranges_.AddBlock(NULL, index - live_ranges_.length() + 1, zone());
+    live_ranges_.AddBlock(NULL, index - live_ranges_.length() + 1,
+                          local_zone());
   }
   LiveRange* result = live_ranges_[index];
   if (result == NULL) {
-    result = new (zone()) LiveRange(index, code_zone());
+    result = new (local_zone()) LiveRange(index, code_zone());
     live_ranges_[index] = result;
   }
   return result;
@@ -694,15 +697,15 @@ void RegisterAllocator::Define(LifetimePosition position,
 
   if (range->IsEmpty() || range->Start().Value() > position.Value()) {
     // Can happen if there is a definition without use.
-    range->AddUseInterval(position, position.NextInstruction(), zone());
-    range->AddUsePosition(position.NextInstruction(), NULL, NULL, zone());
+    range->AddUseInterval(position, position.NextInstruction(), local_zone());
+    range->AddUsePosition(position.NextInstruction(), NULL, NULL, local_zone());
   } else {
     range->ShortenTo(position);
   }
 
   if (operand->IsUnallocated()) {
     UnallocatedOperand* unalloc_operand = UnallocatedOperand::cast(operand);
-    range->AddUsePosition(position, unalloc_operand, hint, zone());
+    range->AddUsePosition(position, unalloc_operand, hint, local_zone());
   }
 }
 
@@ -715,9 +718,9 @@ void RegisterAllocator::Use(LifetimePosition block_start,
   if (range == NULL) return;
   if (operand->IsUnallocated()) {
     UnallocatedOperand* unalloc_operand = UnallocatedOperand::cast(operand);
-    range->AddUsePosition(position, unalloc_operand, hint, zone());
+    range->AddUsePosition(position, unalloc_operand, hint, local_zone());
   }
-  range->AddUseInterval(block_start, position, zone());
+  range->AddUseInterval(block_start, position, local_zone());
 }
 
 
@@ -1023,7 +1026,7 @@ void RegisterAllocator::ProcessInstructions(const InstructionBlock* block,
           if (!IsOutputRegisterOf(instr, i)) {
             LiveRange* range = FixedLiveRangeFor(i);
             range->AddUseInterval(curr_position, curr_position.InstructionEnd(),
-                                  zone());
+                                  local_zone());
           }
         }
       }
@@ -1033,7 +1036,7 @@ void RegisterAllocator::ProcessInstructions(const InstructionBlock* block,
           if (!IsOutputDoubleRegisterOf(instr, i)) {
             LiveRange* range = FixedDoubleLiveRangeFor(i);
             range->AddUseInterval(curr_position, curr_position.InstructionEnd(),
-                                  zone());
+                                  local_zone());
           }
         }
       }
@@ -1160,9 +1163,8 @@ bool RegisterAllocator::Allocate(PipelineStatistics* stats) {
 
 
 void RegisterAllocator::MeetRegisterConstraints() {
-  for (int i = 0; i < code()->InstructionBlockCount(); ++i) {
-    MeetRegisterConstraints(
-        code()->InstructionBlockAt(BasicBlock::RpoNumber::FromInt(i)));
+  for (auto block : code()->instruction_blocks()) {
+    MeetRegisterConstraints(block);
     if (!AllocationOk()) return;
   }
 }
@@ -1170,55 +1172,9 @@ void RegisterAllocator::MeetRegisterConstraints() {
 
 void RegisterAllocator::ResolvePhis() {
   // Process the blocks in reverse order.
-  for (int i = code()->InstructionBlockCount() - 1; i >= 0; --i) {
-    ResolvePhis(code()->InstructionBlockAt(BasicBlock::RpoNumber::FromInt(i)));
-  }
-}
-
-
-void RegisterAllocator::ResolveControlFlow(LiveRange* range,
-                                           const InstructionBlock* block,
-                                           const InstructionBlock* pred) {
-  LifetimePosition pred_end =
-      LifetimePosition::FromInstructionIndex(pred->last_instruction_index());
-  LifetimePosition cur_start =
-      LifetimePosition::FromInstructionIndex(block->first_instruction_index());
-  LiveRange* pred_cover = NULL;
-  LiveRange* cur_cover = NULL;
-  LiveRange* cur_range = range;
-  while (cur_range != NULL && (cur_cover == NULL || pred_cover == NULL)) {
-    if (cur_range->CanCover(cur_start)) {
-      DCHECK(cur_cover == NULL);
-      cur_cover = cur_range;
-    }
-    if (cur_range->CanCover(pred_end)) {
-      DCHECK(pred_cover == NULL);
-      pred_cover = cur_range;
-    }
-    cur_range = cur_range->next();
-  }
-
-  if (cur_cover->IsSpilled()) return;
-  DCHECK(pred_cover != NULL && cur_cover != NULL);
-  if (pred_cover != cur_cover) {
-    InstructionOperand* pred_op =
-        pred_cover->CreateAssignedOperand(code_zone());
-    InstructionOperand* cur_op = cur_cover->CreateAssignedOperand(code_zone());
-    if (!pred_op->Equals(cur_op)) {
-      GapInstruction* gap = NULL;
-      if (block->PredecessorCount() == 1) {
-        gap = code()->GapAt(block->first_instruction_index());
-      } else {
-        DCHECK(pred->SuccessorCount() == 1);
-        gap = GetLastGap(pred);
-
-        Instruction* branch = InstructionAt(pred->last_instruction_index());
-        DCHECK(!branch->HasPointerMap());
-        USE(branch);
-      }
-      gap->GetOrCreateParallelMove(GapInstruction::START, code_zone())
-          ->AddMove(pred_op, cur_op, code_zone());
-    }
+  for (auto i = code()->instruction_blocks().rbegin();
+       i != code()->instruction_blocks().rend(); ++i) {
+    ResolvePhis(*i);
   }
 }
 
@@ -1288,20 +1244,146 @@ bool RegisterAllocator::CanEagerlyResolveControlFlow(
 }
 
 
+namespace {
+
+class LiveRangeBound {
+ public:
+  explicit LiveRangeBound(const LiveRange* range)
+      : range_(range), start_(range->Start()), end_(range->End()) {
+    DCHECK(!range->IsEmpty());
+  }
+
+  bool CanCover(LifetimePosition position) {
+    return start_.Value() <= position.Value() &&
+           position.Value() < end_.Value();
+  }
+
+  const LiveRange* const range_;
+  const LifetimePosition start_;
+  const LifetimePosition end_;
+
+ private:
+  DISALLOW_COPY_AND_ASSIGN(LiveRangeBound);
+};
+
+
+struct FindResult {
+  const LiveRange* cur_cover_;
+  const LiveRange* pred_cover_;
+};
+
+
+class LiveRangeBoundArray {
+ public:
+  LiveRangeBoundArray() : length_(0), start_(nullptr) {}
+
+  bool ShouldInitialize() { return start_ == NULL; }
+
+  void Initialize(Zone* zone, const LiveRange* const range) {
+    size_t length = 0;
+    for (const LiveRange* i = range; i != NULL; i = i->next()) length++;
+    start_ = zone->NewArray<LiveRangeBound>(static_cast<int>(length));
+    length_ = length;
+    LiveRangeBound* curr = start_;
+    for (const LiveRange* i = range; i != NULL; i = i->next(), ++curr) {
+      new (curr) LiveRangeBound(i);
+    }
+  }
+
+  LiveRangeBound* Find(const LifetimePosition position) const {
+    size_t left_index = 0;
+    size_t right_index = length_;
+    while (true) {
+      size_t current_index = left_index + (right_index - left_index) / 2;
+      DCHECK(right_index > current_index);
+      LiveRangeBound* bound = &start_[current_index];
+      if (bound->start_.Value() <= position.Value()) {
+        if (position.Value() < bound->end_.Value()) return bound;
+        DCHECK(left_index < current_index);
+        left_index = current_index;
+      } else {
+        right_index = current_index;
+      }
+    }
+  }
+
+  void Find(const InstructionBlock* block, const InstructionBlock* pred,
+            FindResult* result) const {
+    const LifetimePosition pred_end =
+        LifetimePosition::FromInstructionIndex(pred->last_instruction_index());
+    LiveRangeBound* bound = Find(pred_end);
+    result->pred_cover_ = bound->range_;
+    const LifetimePosition cur_start = LifetimePosition::FromInstructionIndex(
+        block->first_instruction_index());
+    // Common case.
+    if (bound->CanCover(cur_start)) {
+      result->cur_cover_ = bound->range_;
+      return;
+    }
+    result->cur_cover_ = Find(cur_start)->range_;
+    DCHECK(result->pred_cover_ != NULL && result->cur_cover_ != NULL);
+  }
+
+ private:
+  size_t length_;
+  LiveRangeBound* start_;
+
+  DISALLOW_COPY_AND_ASSIGN(LiveRangeBoundArray);
+};
+
+
+class LiveRangeFinder {
+ public:
+  explicit LiveRangeFinder(const RegisterAllocator& allocator)
+      : allocator_(allocator),
+        bounds_length_(allocator.live_ranges().length()),
+        bounds_(allocator.local_zone()->NewArray<LiveRangeBoundArray>(
+            bounds_length_)) {
+    for (int i = 0; i < bounds_length_; ++i) {
+      new (&bounds_[i]) LiveRangeBoundArray();
+    }
+  }
+
+  LiveRangeBoundArray* ArrayFor(int operand_index) {
+    DCHECK(operand_index < bounds_length_);
+    const LiveRange* range = allocator_.live_ranges()[operand_index];
+    DCHECK(range != nullptr && !range->IsEmpty());
+    LiveRangeBoundArray* array = &bounds_[operand_index];
+    if (array->ShouldInitialize()) {
+      array->Initialize(allocator_.local_zone(), range);
+    }
+    return array;
+  }
+
+ private:
+  const RegisterAllocator& allocator_;
+  const int bounds_length_;
+  LiveRangeBoundArray* const bounds_;
+
+  DISALLOW_COPY_AND_ASSIGN(LiveRangeFinder);
+};
+
+}  // namespace
+
+
 void RegisterAllocator::ResolveControlFlow() {
-  for (int block_id = 1; block_id < code()->InstructionBlockCount();
-       ++block_id) {
-    const InstructionBlock* block =
-        code()->InstructionBlockAt(BasicBlock::RpoNumber::FromInt(block_id));
+  // Lazily linearize live ranges in memory for fast lookup.
+  LiveRangeFinder finder(*this);
+  for (auto block : code()->instruction_blocks()) {
     if (CanEagerlyResolveControlFlow(block)) continue;
     BitVector* live = live_in_sets_[block->rpo_number().ToInt()];
     BitVector::Iterator iterator(live);
     while (!iterator.Done()) {
-      int operand_index = iterator.Current();
+      LiveRangeBoundArray* array = finder.ArrayFor(iterator.Current());
       for (auto pred : block->predecessors()) {
-        const InstructionBlock* cur = code()->InstructionBlockAt(pred);
-        LiveRange* cur_range = LiveRangeFor(operand_index);
-        ResolveControlFlow(cur_range, block, cur);
+        FindResult result;
+        const InstructionBlock* pred_block = code()->InstructionBlockAt(pred);
+        array->Find(block, pred_block, &result);
+        if (result.cur_cover_ == result.pred_cover_ ||
+            result.cur_cover_->IsSpilled())
+          continue;
+        ResolveControlFlow(block, result.cur_cover_, pred_block,
+                           result.pred_cover_);
       }
       iterator.Advance();
     }
@@ -1309,6 +1391,30 @@ void RegisterAllocator::ResolveControlFlow() {
 }
 
 
+void RegisterAllocator::ResolveControlFlow(const InstructionBlock* block,
+                                           const LiveRange* cur_cover,
+                                           const InstructionBlock* pred,
+                                           const LiveRange* pred_cover) {
+  InstructionOperand* pred_op = pred_cover->CreateAssignedOperand(code_zone());
+  InstructionOperand* cur_op = cur_cover->CreateAssignedOperand(code_zone());
+  if (!pred_op->Equals(cur_op)) {
+    GapInstruction* gap = NULL;
+    if (block->PredecessorCount() == 1) {
+      gap = code()->GapAt(block->first_instruction_index());
+    } else {
+      DCHECK(pred->SuccessorCount() == 1);
+      gap = GetLastGap(pred);
+
+      Instruction* branch = InstructionAt(pred->last_instruction_index());
+      DCHECK(!branch->HasPointerMap());
+      USE(branch);
+    }
+    gap->GetOrCreateParallelMove(GapInstruction::START, code_zone())
+        ->AddMove(pred_op, cur_op, code_zone());
+  }
+}
+
+
 void RegisterAllocator::BuildLiveRanges() {
   InitializeLivenessAnalysis();
   // Process the blocks in reverse order.
@@ -1371,7 +1477,7 @@ void RegisterAllocator::BuildLiveRanges() {
       while (!iterator.Done()) {
         int operand_index = iterator.Current();
         LiveRange* range = LiveRangeFor(operand_index);
-        range->EnsureInterval(start, end, zone());
+        range->EnsureInterval(start, end, local_zone());
         iterator.Advance();
       }
 
@@ -1667,13 +1773,13 @@ RegisterKind RegisterAllocator::RequiredRegisterKind(
 
 void RegisterAllocator::AddToActive(LiveRange* range) {
   TraceAlloc("Add live range %d to active\n", range->id());
-  active_live_ranges_.Add(range, zone());
+  active_live_ranges_.Add(range, local_zone());
 }
 
 
 void RegisterAllocator::AddToInactive(LiveRange* range) {
   TraceAlloc("Add live range %d to inactive\n", range->id());
-  inactive_live_ranges_.Add(range, zone());
+  inactive_live_ranges_.Add(range, local_zone());
 }
 
 
@@ -1685,13 +1791,13 @@ void RegisterAllocator::AddToUnhandledSorted(LiveRange* range) {
     LiveRange* cur_range = unhandled_live_ranges_.at(i);
     if (range->ShouldBeAllocatedBefore(cur_range)) {
       TraceAlloc("Add live range %d to unhandled at %d\n", range->id(), i + 1);
-      unhandled_live_ranges_.InsertAt(i + 1, range, zone());
+      unhandled_live_ranges_.InsertAt(i + 1, range, local_zone());
       DCHECK(UnhandledIsSorted());
       return;
     }
   }
   TraceAlloc("Add live range %d to unhandled at start\n", range->id());
-  unhandled_live_ranges_.InsertAt(0, range, zone());
+  unhandled_live_ranges_.InsertAt(0, range, local_zone());
   DCHECK(UnhandledIsSorted());
 }
 
@@ -1700,7 +1806,7 @@ void RegisterAllocator::AddToUnhandledUnsorted(LiveRange* range) {
   if (range == NULL || range->IsEmpty()) return;
   DCHECK(!range->HasRegisterAssigned() && !range->IsSpilled());
   TraceAlloc("Add live range %d to unhandled unsorted at end\n", range->id());
-  unhandled_live_ranges_.Add(range, zone());
+  unhandled_live_ranges_.Add(range, local_zone());
 }
 
 
@@ -1742,7 +1848,7 @@ void RegisterAllocator::FreeSpillSlot(LiveRange* range) {
   InstructionOperand* spill_operand = range->TopLevel()->GetSpillOperand();
   if (spill_operand->IsConstant()) return;
   if (spill_operand->index() >= 0) {
-    reusable_slots_.Add(range, zone());
+    reusable_slots_.Add(range, local_zone());
   }
 }
 
@@ -1771,7 +1877,7 @@ void RegisterAllocator::ActiveToHandled(LiveRange* range) {
 void RegisterAllocator::ActiveToInactive(LiveRange* range) {
   DCHECK(active_live_ranges_.Contains(range));
   active_live_ranges_.RemoveElement(range);
-  inactive_live_ranges_.Add(range, zone());
+  inactive_live_ranges_.Add(range, local_zone());
   TraceAlloc("Moving live range %d from active to inactive\n", range->id());
 }
 
@@ -1787,7 +1893,7 @@ void RegisterAllocator::InactiveToHandled(LiveRange* range) {
 void RegisterAllocator::InactiveToActive(LiveRange* range) {
   DCHECK(inactive_live_ranges_.Contains(range));
   inactive_live_ranges_.RemoveElement(range);
-  active_live_ranges_.Add(range, zone());
+  active_live_ranges_.Add(range, local_zone());
   TraceAlloc("Moving live range %d from inactive to active\n", range->id());
 }
 
@@ -2063,7 +2169,7 @@ LiveRange* RegisterAllocator::SplitRangeAt(LiveRange* range,
   int vreg = GetVirtualRegister();
   if (!AllocationOk()) return NULL;
   LiveRange* result = LiveRangeFor(vreg);
-  range->SplitAt(pos, result, zone());
+  range->SplitAt(pos, result, local_zone());
   return result;
 }
 
@@ -2171,10 +2277,10 @@ void RegisterAllocator::Spill(LiveRange* range) {
       RegisterKind kind = range->Kind();
       int index = frame()->AllocateSpillSlot(kind == DOUBLE_REGISTERS);
       if (kind == DOUBLE_REGISTERS) {
-        op = DoubleStackSlotOperand::Create(index, zone());
+        op = DoubleStackSlotOperand::Create(index, local_zone());
       } else {
         DCHECK(kind == GENERAL_REGISTERS);
-        op = StackSlotOperand::Create(index, zone());
+        op = StackSlotOperand::Create(index, local_zone());
       }
     }
     first->SetSpillOperand(op);

src/compiler/register-allocator.h

@@ -186,12 +186,15 @@ class LiveRange FINAL : public ZoneObject {
   UsePosition* first_pos() const { return first_pos_; }
   LiveRange* parent() const { return parent_; }
   LiveRange* TopLevel() { return (parent_ == NULL) ? this : parent_; }
+  const LiveRange* TopLevel() const {
+    return (parent_ == NULL) ? this : parent_;
+  }
   LiveRange* next() const { return next_; }
   bool IsChild() const { return parent() != NULL; }
   int id() const { return id_; }
   bool IsFixed() const { return id_ < 0; }
   bool IsEmpty() const { return first_interval() == NULL; }
-  InstructionOperand* CreateAssignedOperand(Zone* zone);
+  InstructionOperand* CreateAssignedOperand(Zone* zone) const;
   int assigned_register() const { return assigned_register_; }
   int spill_start_index() const { return spill_start_index_; }
   void set_assigned_register(int reg, Zone* zone);
@@ -337,6 +340,8 @@ class RegisterAllocator FINAL {
     return fixed_double_live_ranges_;
   }
   InstructionSequence* code() const { return code_; }
+  // This zone is for datastructures only needed during register allocation.
+  Zone* local_zone() const { return local_zone_; }
 
  private:
   int GetVirtualRegister() {
@@ -356,9 +361,6 @@ class RegisterAllocator FINAL {
   // Returns the register kind required by the given virtual register.
   RegisterKind RequiredRegisterKind(int virtual_register) const;
 
-  // This zone is for datastructures only needed during register allocation.
-  Zone* zone() const { return zone_; }
-
   // This zone is for InstructionOperands and moves that live beyond register
   // allocation.
   Zone* code_zone() const { return code()->zone(); }
@@ -465,8 +467,10 @@ class RegisterAllocator FINAL {
   bool IsBlockBoundary(LifetimePosition pos);
 
   // Helper methods for resolving control flow.
-  void ResolveControlFlow(LiveRange* range, const InstructionBlock* block,
-                          const InstructionBlock* pred);
+  void ResolveControlFlow(const InstructionBlock* block,
+                          const LiveRange* cur_cover,
+                          const InstructionBlock* pred,
+                          const LiveRange* pred_cover);
 
   void SetLiveRangeAssignedRegister(LiveRange* range, int reg);
 
@@ -494,7 +498,7 @@ class RegisterAllocator FINAL {
   const char* debug_name() const { return debug_name_; }
   const RegisterConfiguration* config() const { return config_; }
 
-  Zone* const zone_;
+  Zone* const local_zone_;
   Frame* const frame_;
   InstructionSequence* const code_;
   const char* const debug_name_;