src/hydrogen.h

// Copyright 2012 the V8 project authors. All rights reserved.
// Redistribution and use in source and binary forms, with or without
// modification, are permitted provided that the following conditions are
// met:
//
//     * Redistributions of source code must retain the above copyright
//       notice, this list of conditions and the following disclaimer.
//     * Redistributions in binary form must reproduce the above
//       copyright notice, this list of conditions and the following
//       disclaimer in the documentation and/or other materials provided
//       with the distribution.
//     * Neither the name of Google Inc. nor the names of its
//       contributors may be used to endorse or promote products derived
//       from this software without specific prior written permission.
//
// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

#ifndef V8_HYDROGEN_H_
#define V8_HYDROGEN_H_

#include "v8.h"

#include "allocation.h"
#include "ast.h"
#include "compiler.h"
#include "hydrogen-instructions.h"
#include "zone.h"
#include "scopes.h"

namespace v8 {
namespace internal {

// Forward declarations.
class BitVector;
class FunctionState;
class HEnvironment;
class HGraph;
class HLoopInformation;
class HOsrBuilder;
class HTracer;
class LAllocator;
class LChunk;
class LiveRange;


class HBasicBlock V8_FINAL : public ZoneObject {
 public:
  explicit HBasicBlock(HGraph* graph);
  ~HBasicBlock() { }

  // Simple accessors.
  int block_id() const { return block_id_; }
  void set_block_id(int id) { block_id_ = id; }
  HGraph* graph() const { return graph_; }
  Isolate* isolate() const;
  const ZoneList<HPhi*>* phis() const { return &phis_; }
  HInstruction* first() const { return first_; }
  HInstruction* last() const { return last_; }
  void set_last(HInstruction* instr) { last_ = instr; }
  HControlInstruction* end() const { return end_; }
  HLoopInformation* loop_information() const { return loop_information_; }
  HLoopInformation* current_loop() const {
    return IsLoopHeader() ? loop_information()
                          : (parent_loop_header() != NULL
                            ? parent_loop_header()->loop_information() : NULL);
  }
  const ZoneList<HBasicBlock*>* predecessors() const { return &predecessors_; }
  bool HasPredecessor() const { return predecessors_.length() > 0; }
  const ZoneList<HBasicBlock*>* dominated_blocks() const {
    return &dominated_blocks_;
  }
  const ZoneList<int>* deleted_phis() const {
    return &deleted_phis_;
  }
  void RecordDeletedPhi(int merge_index) {
    deleted_phis_.Add(merge_index, zone());
  }
  HBasicBlock* dominator() const { return dominator_; }
  HEnvironment* last_environment() const { return last_environment_; }
  int argument_count() const { return argument_count_; }
  void set_argument_count(int count) { argument_count_ = count; }
  int first_instruction_index() const { return first_instruction_index_; }
  void set_first_instruction_index(int index) {
    first_instruction_index_ = index;
  }
  int last_instruction_index() const { return last_instruction_index_; }
  void set_last_instruction_index(int index) {
    last_instruction_index_ = index;
  }
  bool is_osr_entry() { return is_osr_entry_; }
  void set_osr_entry() { is_osr_entry_ = true; }

  void AttachLoopInformation();
  void DetachLoopInformation();
  bool IsLoopHeader() const { return loop_information() != NULL; }
  bool IsStartBlock() const { return block_id() == 0; }
  void PostProcessLoopHeader(IterationStatement* stmt);

  bool IsFinished() const { return end_ != NULL; }
  void AddPhi(HPhi* phi);
  void RemovePhi(HPhi* phi);
  void AddInstruction(HInstruction* instr);
  bool Dominates(HBasicBlock* other) const;
  int LoopNestingDepth() const;

  void SetInitialEnvironment(HEnvironment* env);
  void ClearEnvironment() {
    ASSERT(IsFinished());
    ASSERT(end()->SuccessorCount() == 0);
    last_environment_ = NULL;
  }
  bool HasEnvironment() const { return last_environment_ != NULL; }
  void UpdateEnvironment(HEnvironment* env);
  HBasicBlock* parent_loop_header() const { return parent_loop_header_; }

  void set_parent_loop_header(HBasicBlock* block) {
    ASSERT(parent_loop_header_ == NULL);
    parent_loop_header_ = block;
  }

  bool HasParentLoopHeader() const { return parent_loop_header_ != NULL; }

  void SetJoinId(BailoutId ast_id);

  void Finish(HControlInstruction* last);
  void FinishExit(HControlInstruction* instruction);
  void Goto(HBasicBlock* block,
            FunctionState* state = NULL,
            bool add_simulate = true);
  void GotoNoSimulate(HBasicBlock* block) {
    Goto(block, NULL, false);
  }

  int PredecessorIndexOf(HBasicBlock* predecessor) const;
  HPhi* AddNewPhi(int merged_index);
  HSimulate* AddNewSimulate(BailoutId ast_id,
                            RemovableSimulate removable = FIXED_SIMULATE) {
    HSimulate* instr = CreateSimulate(ast_id, removable);
    AddInstruction(instr);
    return instr;
  }
  void AssignCommonDominator(HBasicBlock* other);
  void AssignLoopSuccessorDominators();

  // Add the inlined function exit sequence, adding an HLeaveInlined
  // instruction and updating the bailout environment.
  void AddLeaveInlined(HValue* return_value, FunctionState* state);

  // If a target block is tagged as an inline function return, all
  // predecessors should contain the inlined exit sequence:
  //
  // LeaveInlined
  // Simulate (caller's environment)
  // Goto (target block)
  bool IsInlineReturnTarget() const { return is_inline_return_target_; }
  void MarkAsInlineReturnTarget(HBasicBlock* inlined_entry_block) {
    is_inline_return_target_ = true;
    inlined_entry_block_ = inlined_entry_block;
  }
  HBasicBlock* inlined_entry_block() { return inlined_entry_block_; }

  bool IsDeoptimizing() const { return is_deoptimizing_; }
  void MarkAsDeoptimizing() { is_deoptimizing_ = true; }

  bool IsLoopSuccessorDominator() const {
    return dominates_loop_successors_;
  }
  void MarkAsLoopSuccessorDominator() {
    dominates_loop_successors_ = true;
  }

  inline Zone* zone() const;

#ifdef DEBUG
  void Verify();
#endif

 private:
  friend class HGraphBuilder;

  void RegisterPredecessor(HBasicBlock* pred);
  void AddDominatedBlock(HBasicBlock* block);

  HSimulate* CreateSimulate(BailoutId ast_id, RemovableSimulate removable);

  int block_id_;
  HGraph* graph_;
  ZoneList<HPhi*> phis_;
  HInstruction* first_;
  HInstruction* last_;
  HControlInstruction* end_;
  HLoopInformation* loop_information_;
  ZoneList<HBasicBlock*> predecessors_;
  HBasicBlock* dominator_;
  ZoneList<HBasicBlock*> dominated_blocks_;
  HEnvironment* last_environment_;
  // Outgoing parameter count at block exit, set during lithium translation.
  int argument_count_;
  // Instruction indices into the lithium code stream.
  int first_instruction_index_;
  int last_instruction_index_;
  ZoneList<int> deleted_phis_;
  HBasicBlock* parent_loop_header_;
  // For blocks marked as inline return target: the block with HEnterInlined.
  HBasicBlock* inlined_entry_block_;
  bool is_inline_return_target_ : 1;
  bool is_deoptimizing_ : 1;
  bool dominates_loop_successors_ : 1;
  bool is_osr_entry_ : 1;
};


class HPredecessorIterator V8_FINAL BASE_EMBEDDED {
 public:
  explicit HPredecessorIterator(HBasicBlock* block)
      : predecessor_list_(block->predecessors()), current_(0) { }

  bool Done() { return current_ >= predecessor_list_->length(); }
  HBasicBlock* Current() { return predecessor_list_->at(current_); }
  void Advance() { current_++; }

 private:
  const ZoneList<HBasicBlock*>* predecessor_list_;
  int current_;
};


class HInstructionIterator V8_FINAL BASE_EMBEDDED {
 public:
  explicit HInstructionIterator(HBasicBlock* block)
      : instr_(block->first()) {
    next_ = Done() ? NULL : instr_->next();
  }

  inline bool Done() const { return instr_ == NULL; }
  inline HInstruction* Current() { return instr_; }
  inline void Advance() {
    instr_ = next_;
    next_ = Done() ? NULL : instr_->next();
  }

 private:
  HInstruction* instr_;
  HInstruction* next_;
};


class HLoopInformation V8_FINAL : public ZoneObject {
 public:
  HLoopInformation(HBasicBlock* loop_header, Zone* zone)
      : back_edges_(4, zone),
        loop_header_(loop_header),
        blocks_(8, zone),
        stack_check_(NULL) {
    blocks_.Add(loop_header, zone);
  }
  ~HLoopInformation() {}

  const ZoneList<HBasicBlock*>* back_edges() const { return &back_edges_; }
  const ZoneList<HBasicBlock*>* blocks() const { return &blocks_; }
  HBasicBlock* loop_header() const { return loop_header_; }
  HBasicBlock* GetLastBackEdge() const;
  void RegisterBackEdge(HBasicBlock* block);

  HStackCheck* stack_check() const { return stack_check_; }
  void set_stack_check(HStackCheck* stack_check) {
    stack_check_ = stack_check;
  }

  bool IsNestedInThisLoop(HLoopInformation* other) {
    while (other != NULL) {
      if (other == this) {
        return true;
      }
      other = other->parent_loop();
    }
    return false;
  }
  HLoopInformation* parent_loop() {
    HBasicBlock* parent_header = loop_header()->parent_loop_header();
    return parent_header != NULL ? parent_header->loop_information() : NULL;
  }

 private:
  void AddBlock(HBasicBlock* block);

  ZoneList<HBasicBlock*> back_edges_;
  HBasicBlock* loop_header_;
  ZoneList<HBasicBlock*> blocks_;
  HStackCheck* stack_check_;
};


class BoundsCheckTable;
class InductionVariableBlocksTable;
class HGraph V8_FINAL : public ZoneObject {
 public:
  explicit HGraph(CompilationInfo* info);

  Isolate* isolate() const { return isolate_; }
  Zone* zone() const { return zone_; }
  CompilationInfo* info() const { return info_; }

  const ZoneList<HBasicBlock*>* blocks() const { return &blocks_; }
  const ZoneList<HPhi*>* phi_list() const { return phi_list_; }
  HBasicBlock* entry_block() const { return entry_block_; }
  HEnvironment* start_environment() const { return start_environment_; }

  void FinalizeUniqueValueIds();
  bool ProcessArgumentsObject();
  void OrderBlocks();
  void AssignDominators();
  void RestoreActualValues();

  // Returns false if there are phi-uses of the arguments-object
  // which are not supported by the optimizing compiler.
  bool CheckArgumentsPhiUses();

  // Returns false if there are phi-uses of an uninitialized const
  // which are not supported by the optimizing compiler.
  bool CheckConstPhiUses();

  void CollectPhis();

  void set_undefined_constant(HConstant* constant) {
    undefined_constant_.set(constant);
  }
  HConstant* GetConstantUndefined() const { return undefined_constant_.get(); }
  HConstant* GetConstant0();
  HConstant* GetConstant1();
  HConstant* GetConstantMinus1();
  HConstant* GetConstantTrue();
  HConstant* GetConstantFalse();
  HConstant* GetConstantHole();
  HConstant* GetConstantNull();
  HConstant* GetInvalidContext();

  bool IsStandardConstant(HConstant* constant);

  HBasicBlock* CreateBasicBlock();
  HArgumentsObject* GetArgumentsObject() const {
    return arguments_object_.get();
  }

  void SetArgumentsObject(HArgumentsObject* object) {
    arguments_object_.set(object);
  }

  int GetMaximumValueID() const { return values_.length(); }
  int GetNextBlockID() { return next_block_id_++; }
  int GetNextValueID(HValue* value) {
    values_.Add(value, zone());
    return values_.length() - 1;
  }
  HValue* LookupValue(int id) const {
    if (id >= 0 && id < values_.length()) return values_[id];
    return NULL;
  }

  bool Optimize(BailoutReason* bailout_reason);

#ifdef DEBUG
  void Verify(bool do_full_verify) const;
#endif

  bool has_osr() {
    return osr_ != NULL;
  }

  void set_osr(HOsrBuilder* osr) {
    osr_ = osr;
  }

  HOsrBuilder* osr() {
    return osr_;
  }

  int update_type_change_checksum(int delta) {
    type_change_checksum_ += delta;
    return type_change_checksum_;
  }

  void update_maximum_environment_size(int environment_size) {
    if (environment_size > maximum_environment_size_) {
      maximum_environment_size_ = environment_size;
    }
  }
  int maximum_environment_size() { return maximum_environment_size_; }

  bool use_optimistic_licm() {
    return use_optimistic_licm_;
  }

  void set_use_optimistic_licm(bool value) {
    use_optimistic_licm_ = value;
  }

  bool has_soft_deoptimize() {
    return has_soft_deoptimize_;
  }

  void set_has_soft_deoptimize(bool value) {
    has_soft_deoptimize_ = value;
  }

  void MarkRecursive() {
    is_recursive_ = true;
  }

  bool is_recursive() const {
    return is_recursive_;
  }

  void MarkDependsOnEmptyArrayProtoElements() {
    // Add map dependency if not already added.
    if (depends_on_empty_array_proto_elements_) return;
    isolate()->initial_object_prototype()->map()->AddDependentCompilationInfo(
        DependentCode::kElementsCantBeAddedGroup, info());
    isolate()->initial_array_prototype()->map()->AddDependentCompilationInfo(
        DependentCode::kElementsCantBeAddedGroup, info());
    depends_on_empty_array_proto_elements_ = true;
  }

  bool depends_on_empty_array_proto_elements() {
    return depends_on_empty_array_proto_elements_;
  }

  bool has_uint32_instructions() {
    ASSERT(uint32_instructions_ == NULL || !uint32_instructions_->is_empty());
    return uint32_instructions_ != NULL;
  }

  ZoneList<HInstruction*>* uint32_instructions() {
    ASSERT(uint32_instructions_ == NULL || !uint32_instructions_->is_empty());
    return uint32_instructions_;
  }

  void RecordUint32Instruction(HInstruction* instr) {
    ASSERT(uint32_instructions_ == NULL || !uint32_instructions_->is_empty());
    if (uint32_instructions_ == NULL) {
      uint32_instructions_ = new(zone()) ZoneList<HInstruction*>(4, zone());
    }
    uint32_instructions_->Add(instr, zone());
  }

  void IncrementInNoSideEffectsScope() { no_side_effects_scope_count_++; }
  void DecrementInNoSideEffectsScope() { no_side_effects_scope_count_--; }
  bool IsInsideNoSideEffectsScope() { return no_side_effects_scope_count_ > 0; }

 private:
  HConstant* GetConstant(SetOncePointer<HConstant>* pointer,
                         int32_t integer_value);

  template<class Phase>
  void Run() {
    Phase phase(this);
    phase.Run();
  }

  void EliminateRedundantBoundsChecksUsingInductionVariables();

  Isolate* isolate_;
  int next_block_id_;
  HBasicBlock* entry_block_;
  HEnvironment* start_environment_;
  ZoneList<HBasicBlock*> blocks_;
  ZoneList<HValue*> values_;
  ZoneList<HPhi*>* phi_list_;
  ZoneList<HInstruction*>* uint32_instructions_;
  SetOncePointer<HConstant> undefined_constant_;
  SetOncePointer<HConstant> constant_0_;
  SetOncePointer<HConstant> constant_1_;
  SetOncePointer<HConstant> constant_minus1_;
  SetOncePointer<HConstant> constant_true_;
  SetOncePointer<HConstant> constant_false_;
  SetOncePointer<HConstant> constant_the_hole_;
  SetOncePointer<HConstant> constant_null_;
  SetOncePointer<HConstant> constant_invalid_context_;
  SetOncePointer<HArgumentsObject> arguments_object_;

  HOsrBuilder* osr_;

  CompilationInfo* info_;
  Zone* zone_;

  bool is_recursive_;
  bool use_optimistic_licm_;
  bool has_soft_deoptimize_;
  bool depends_on_empty_array_proto_elements_;
  int type_change_checksum_;
  int maximum_environment_size_;
  int no_side_effects_scope_count_;

  DISALLOW_COPY_AND_ASSIGN(HGraph);
};


Zone* HBasicBlock::zone() const { return graph_->zone(); }


// Type of stack frame an environment might refer to.
enum FrameType {
  JS_FUNCTION,
  JS_CONSTRUCT,
  JS_GETTER,
  JS_SETTER,
  ARGUMENTS_ADAPTOR,
  STUB
};


class HEnvironment V8_FINAL : public ZoneObject {
 public:
  HEnvironment(HEnvironment* outer,
               Scope* scope,
               Handle<JSFunction> closure,
               Zone* zone);

  HEnvironment(Zone* zone, int parameter_count);

  HEnvironment* arguments_environment() {
    return outer()->frame_type() == ARGUMENTS_ADAPTOR ? outer() : this;
  }

  // Simple accessors.
  Handle<JSFunction> closure() const { return closure_; }
  const ZoneList<HValue*>* values() const { return &values_; }
  const GrowableBitVector* assigned_variables() const {
    return &assigned_variables_;
  }
  FrameType frame_type() const { return frame_type_; }
  int parameter_count() const { return parameter_count_; }
  int specials_count() const { return specials_count_; }
  int local_count() const { return local_count_; }
  HEnvironment* outer() const { return outer_; }
  int pop_count() const { return pop_count_; }
  int push_count() const { return push_count_; }

  BailoutId ast_id() const { return ast_id_; }
  void set_ast_id(BailoutId id) { ast_id_ = id; }

  HEnterInlined* entry() const { return entry_; }
  void set_entry(HEnterInlined* entry) { entry_ = entry; }

  int length() const { return values_.length(); }

  int first_expression_index() const {
    return parameter_count() + specials_count() + local_count();
  }

  int first_local_index() const {
    return parameter_count() + specials_count();
  }

  void Bind(Variable* variable, HValue* value) {
    Bind(IndexFor(variable), value);
  }

  void Bind(int index, HValue* value);

  void BindContext(HValue* value) {
    Bind(parameter_count(), value);
  }

  HValue* Lookup(Variable* variable) const {
    return Lookup(IndexFor(variable));
  }

  HValue* Lookup(int index) const {
    HValue* result = values_[index];
    ASSERT(result != NULL);
    return result;
  }

  HValue* context() const {
    // Return first special.
    return Lookup(parameter_count());
  }

  void Push(HValue* value) {
    ASSERT(value != NULL);
    ++push_count_;
    values_.Add(value, zone());
  }

  HValue* Pop() {
    ASSERT(!ExpressionStackIsEmpty());
    if (push_count_ > 0) {
      --push_count_;
    } else {
      ++pop_count_;
    }
    return values_.RemoveLast();
  }

  void Drop(int count);

  HValue* Top() const { return ExpressionStackAt(0); }

  bool ExpressionStackIsEmpty() const;

  HValue* ExpressionStackAt(int index_from_top) const {
    int index = length() - index_from_top - 1;
    ASSERT(HasExpressionAt(index));
    return values_[index];
  }

  void SetExpressionStackAt(int index_from_top, HValue* value);

  HEnvironment* Copy() const;
  HEnvironment* CopyWithoutHistory() const;
  HEnvironment* CopyAsLoopHeader(HBasicBlock* block) const;

  // Create an "inlined version" of this environment, where the original
  // environment is the outer environment but the top expression stack
  // elements are moved to an inner environment as parameters.
  HEnvironment* CopyForInlining(Handle<JSFunction> target,
                                int arguments,
                                FunctionLiteral* function,
                                HConstant* undefined,
                                InliningKind inlining_kind,
                                bool undefined_receiver) const;

  static bool UseUndefinedReceiver(Handle<JSFunction> closure,
                                   FunctionLiteral* function,
                                   CallKind call_kind,
                                   InliningKind inlining_kind) {
    return (closure->shared()->native() || !function->is_classic_mode()) &&
        call_kind == CALL_AS_FUNCTION && inlining_kind != CONSTRUCT_CALL_RETURN;
  }

  HEnvironment* DiscardInlined(bool drop_extra) {
    HEnvironment* outer = outer_;
    while (outer->frame_type() != JS_FUNCTION) outer = outer->outer_;
    if (drop_extra) outer->Drop(1);
    return outer;
  }

  void AddIncomingEdge(HBasicBlock* block, HEnvironment* other);

  void ClearHistory() {
    pop_count_ = 0;
    push_count_ = 0;
    assigned_variables_.Clear();
  }

  void SetValueAt(int index, HValue* value) {
    ASSERT(index < length());
    values_[index] = value;
  }

  // Map a variable to an environment index.  Parameter indices are shifted
  // by 1 (receiver is parameter index -1 but environment index 0).
  // Stack-allocated local indices are shifted by the number of parameters.
  int IndexFor(Variable* variable) const {
    ASSERT(variable->IsStackAllocated());
    int shift = variable->IsParameter()
        ? 1
        : parameter_count_ + specials_count_;
    return variable->index() + shift;
  }

  bool is_local_index(int i) const {
    return i >= first_local_index() && i < first_expression_index();
  }

  bool is_parameter_index(int i) const {
    return i >= 0 && i < parameter_count();
  }

  bool is_special_index(int i) const {
    return i >= parameter_count() && i < parameter_count() + specials_count();
  }

  void PrintTo(StringStream* stream);
  void PrintToStd();

  Zone* zone() const { return zone_; }

 private:
  HEnvironment(const HEnvironment* other, Zone* zone);

  HEnvironment(HEnvironment* outer,
               Handle<JSFunction> closure,
               FrameType frame_type,
               int arguments,
               Zone* zone);

  // Create an artificial stub environment (e.g. for argument adaptor or
  // constructor stub).
  HEnvironment* CreateStubEnvironment(HEnvironment* outer,
                                      Handle<JSFunction> target,
                                      FrameType frame_type,
                                      int arguments) const;

  // True if index is included in the expression stack part of the environment.
  bool HasExpressionAt(int index) const;

  void Initialize(int parameter_count, int local_count, int stack_height);
  void Initialize(const HEnvironment* other);

  Handle<JSFunction> closure_;
  // Value array [parameters] [specials] [locals] [temporaries].
  ZoneList<HValue*> values_;
  GrowableBitVector assigned_variables_;
  FrameType frame_type_;
  int parameter_count_;
  int specials_count_;
  int local_count_;
  HEnvironment* outer_;
  HEnterInlined* entry_;
  int pop_count_;
  int push_count_;
  BailoutId ast_id_;
  Zone* zone_;
};


class HOptimizedGraphBuilder;

enum ArgumentsAllowedFlag {
  ARGUMENTS_NOT_ALLOWED,
  ARGUMENTS_ALLOWED
};


class HIfContinuation;

// This class is not BASE_EMBEDDED because our inlining implementation uses
// new and delete.
class AstContext {
 public:
  bool IsEffect() const { return kind_ == Expression::kEffect; }
  bool IsValue() const { return kind_ == Expression::kValue; }
  bool IsTest() const { return kind_ == Expression::kTest; }

  // 'Fill' this context with a hydrogen value.  The value is assumed to
  // have already been inserted in the instruction stream (or not need to
  // be, e.g., HPhi).  Call this function in tail position in the Visit
  // functions for expressions.
  virtual void ReturnValue(HValue* value) = 0;

  // Add a hydrogen instruction to the instruction stream (recording an
  // environment simulation if necessary) and then fill this context with
  // the instruction as value.
  virtual void ReturnInstruction(HInstruction* instr, BailoutId ast_id) = 0;

  // Finishes the current basic block and materialize a boolean for
  // value context, nothing for effect, generate a branch for test context.
  // Call this function in tail position in the Visit functions for
  // expressions.
  virtual void ReturnControl(HControlInstruction* instr, BailoutId ast_id) = 0;

  // Finishes the current basic block and materialize a boolean for
  // value context, nothing for effect, generate a branch for test context.
  // Call this function in tail position in the Visit functions for
  // expressions that use an IfBuilder.
  virtual void ReturnContinuation(HIfContinuation* continuation,
                                  BailoutId ast_id) = 0;

  void set_for_typeof(bool for_typeof) { for_typeof_ = for_typeof; }
  bool is_for_typeof() { return for_typeof_; }

 protected:
  AstContext(HOptimizedGraphBuilder* owner, Expression::Context kind);
  virtual ~AstContext();

  HOptimizedGraphBuilder* owner() const { return owner_; }

  inline Zone* zone() const;

  // We want to be able to assert, in a context-specific way, that the stack
  // height makes sense when the context is filled.
#ifdef DEBUG
  int original_length_;
#endif

 private:
  HOptimizedGraphBuilder* owner_;
  Expression::Context kind_;
  AstContext* outer_;
  bool for_typeof_;
};


class EffectContext V8_FINAL : public AstContext {
 public:
  explicit EffectContext(HOptimizedGraphBuilder* owner)
      : AstContext(owner, Expression::kEffect) {
  }
  virtual ~EffectContext();

  virtual void ReturnValue(HValue* value) V8_OVERRIDE;
  virtual void ReturnInstruction(HInstruction* instr,
                                 BailoutId ast_id) V8_OVERRIDE;
  virtual void ReturnControl(HControlInstruction* instr,
                             BailoutId ast_id) V8_OVERRIDE;
  virtual void ReturnContinuation(HIfContinuation* continuation,
                                  BailoutId ast_id) V8_OVERRIDE;
};


class ValueContext V8_FINAL : public AstContext {
 public:
  ValueContext(HOptimizedGraphBuilder* owner, ArgumentsAllowedFlag flag)
      : AstContext(owner, Expression::kValue), flag_(flag) {
  }
  virtual ~ValueContext();

  virtual void ReturnValue(HValue* value) V8_OVERRIDE;
  virtual void ReturnInstruction(HInstruction* instr,
                                 BailoutId ast_id) V8_OVERRIDE;
  virtual void ReturnControl(HControlInstruction* instr,
                             BailoutId ast_id) V8_OVERRIDE;
  virtual void ReturnContinuation(HIfContinuation* continuation,
                                  BailoutId ast_id) V8_OVERRIDE;

  bool arguments_allowed() { return flag_ == ARGUMENTS_ALLOWED; }

 private:
  ArgumentsAllowedFlag flag_;
};


class TestContext V8_FINAL : public AstContext {
 public:
  TestContext(HOptimizedGraphBuilder* owner,
              Expression* condition,
              HBasicBlock* if_true,
              HBasicBlock* if_false)
      : AstContext(owner, Expression::kTest),
        condition_(condition),
        if_true_(if_true),
        if_false_(if_false) {
  }

  virtual void ReturnValue(HValue* value) V8_OVERRIDE;
  virtual void ReturnInstruction(HInstruction* instr,
                                 BailoutId ast_id) V8_OVERRIDE;
  virtual void ReturnControl(HControlInstruction* instr,
                             BailoutId ast_id) V8_OVERRIDE;
  virtual void ReturnContinuation(HIfContinuation* continuation,
                                  BailoutId ast_id) V8_OVERRIDE;

  static TestContext* cast(AstContext* context) {
    ASSERT(context->IsTest());
    return reinterpret_cast<TestContext*>(context);
  }

  Expression* condition() const { return condition_; }
  HBasicBlock* if_true() const { return if_true_; }
  HBasicBlock* if_false() const { return if_false_; }

 private:
  // Build the shared core part of the translation unpacking a value into
  // control flow.
  void BuildBranch(HValue* value);

  Expression* condition_;
  HBasicBlock* if_true_;
  HBasicBlock* if_false_;
};


class FunctionState V8_FINAL {
 public:
  FunctionState(HOptimizedGraphBuilder* owner,
                CompilationInfo* info,
                InliningKind inlining_kind);
  ~FunctionState();

  CompilationInfo* compilation_info() { return compilation_info_; }
  AstContext* call_context() { return call_context_; }
  InliningKind inlining_kind() const { return inlining_kind_; }
  HBasicBlock* function_return() { return function_return_; }
  TestContext* test_context() { return test_context_; }
  void ClearInlinedTestContext() {
    delete test_context_;
    test_context_ = NULL;
  }

  FunctionState* outer() { return outer_; }

  HEnterInlined* entry() { return entry_; }
  void set_entry(HEnterInlined* entry) { entry_ = entry; }

  HArgumentsObject* arguments_object() { return arguments_object_; }
  void set_arguments_object(HArgumentsObject* arguments_object) {
    arguments_object_ = arguments_object;
  }

  HArgumentsElements* arguments_elements() { return arguments_elements_; }
  void set_arguments_elements(HArgumentsElements* arguments_elements) {
    arguments_elements_ = arguments_elements;
  }

  bool arguments_pushed() { return arguments_elements() != NULL; }

 private:
  HOptimizedGraphBuilder* owner_;

  CompilationInfo* compilation_info_;

  // During function inlining, expression context of the call being
  // inlined. NULL when not inlining.
  AstContext* call_context_;

  // The kind of call which is currently being inlined.
  InliningKind inlining_kind_;

  // When inlining in an effect or value context, this is the return block.
  // It is NULL otherwise.  When inlining in a test context, there are a
  // pair of return blocks in the context.  When not inlining, there is no
  // local return point.
  HBasicBlock* function_return_;

  // When inlining a call in a test context, a context containing a pair of
  // return blocks.  NULL in all other cases.
  TestContext* test_context_;

  // When inlining HEnterInlined instruction corresponding to the function
  // entry.
  HEnterInlined* entry_;

  HArgumentsObject* arguments_object_;
  HArgumentsElements* arguments_elements_;

  FunctionState* outer_;
};


class HIfContinuation V8_FINAL {
 public:
  HIfContinuation() { continuation_captured_ = false; }
  ~HIfContinuation() { ASSERT(!continuation_captured_); }

  void Capture(HBasicBlock* true_branch,
               HBasicBlock* false_branch,
               int position) {
    ASSERT(!continuation_captured_);
    true_branch_ = true_branch;
    false_branch_ = false_branch;
    position_ = position;
    continuation_captured_ = true;
  }

  void Continue(HBasicBlock** true_branch,
                HBasicBlock** false_branch,
                int* position) {
    ASSERT(continuation_captured_);
    *true_branch = true_branch_;
    *false_branch = false_branch_;
    if (position != NULL) *position = position_;
    continuation_captured_ = false;
  }

  bool IsTrueReachable() { return true_branch_ != NULL; }
  bool IsFalseReachable() { return false_branch_ != NULL; }
  bool TrueAndFalseReachable() {
    return IsTrueReachable() || IsFalseReachable();
  }

  bool continuation_captured_;
  HBasicBlock* true_branch_;
  HBasicBlock* false_branch_;
  int position_;
};


class HGraphBuilder {
 public:
  explicit HGraphBuilder(CompilationInfo* info)
      : info_(info),
        graph_(NULL),
        current_block_(NULL) {}
  virtual ~HGraphBuilder() {}

  HBasicBlock* current_block() const { return current_block_; }
  void set_current_block(HBasicBlock* block) { current_block_ = block; }
  HEnvironment* environment() const {
    return current_block()->last_environment();
  }
  Zone* zone() const { return info_->zone(); }
  HGraph* graph() const { return graph_; }
  Isolate* isolate() const { return graph_->isolate(); }
  CompilationInfo* top_info() { return info_; }

  HGraph* CreateGraph();

  // Bailout environment manipulation.
  void Push(HValue* value) { environment()->Push(value); }
  HValue* Pop() { return environment()->Pop(); }

  virtual HValue* context() = 0;

  // Adding instructions.
  HInstruction* AddInstruction(HInstruction* instr);

  template<class I>
  HInstruction* NewUncasted() { return I::New(zone(), context()); }

  template<class I>
  I* New() { return I::cast(NewUncasted<I>()); }

  template<class I>
  HInstruction* AddUncasted() { return AddInstruction(NewUncasted<I>());}

  template<class I>
  I* Add() { return I::cast(AddUncasted<I>());}

  template<class I, class P1>
  HInstruction* NewUncasted(P1 p1) {
    return I::New(zone(), context(), p1);
  }

  template<class I, class P1>
  I* New(P1 p1) { return I::cast(NewUncasted<I>(p1)); }

  template<class I, class P1>
  HInstruction* AddUncasted(P1 p1) {
    HInstruction* result = AddInstruction(NewUncasted<I>(p1));
    // Specializations must have their parameters properly casted
    // to avoid landing here.
    ASSERT(!result->IsReturn() && !result->IsSimulate() &&
           !result->IsDeoptimize());
    return result;
  }

  template<class I, class P1>
  I* Add(P1 p1) {
    return I::cast(AddUncasted<I>(p1));
  }

  template<class I, class P1, class P2>
  HInstruction* NewUncasted(P1 p1, P2 p2) {
    return I::New(zone(), context(), p1, p2);
  }

  template<class I, class P1, class P2>
  I* New(P1 p1, P2 p2) {
    return I::cast(NewUncasted<I>(p1, p2));
  }

  template<class I, class P1, class P2>
  HInstruction* AddUncasted(P1 p1, P2 p2) {
    HInstruction* result = AddInstruction(NewUncasted<I>(p1, p2));
    // Specializations must have their parameters properly casted
    // to avoid landing here.
    ASSERT(!result->IsSimulate());
    return result;
  }

  template<class I, class P1, class P2>
  I* Add(P1 p1, P2 p2) {
    return I::cast(AddUncasted<I>(p1, p2));
  }

  template<class I, class P1, class P2, class P3>
  HInstruction* NewUncasted(P1 p1, P2 p2, P3 p3) {
    return I::New(zone(), context(), p1, p2, p3);
  }

  template<class I, class P1, class P2, class P3>
  I* New(P1 p1, P2 p2, P3 p3) {
    return I::cast(NewUncasted<I>(p1, p2, p3));
  }

  template<class I, class P1, class P2, class P3>
  HInstruction* AddUncasted(P1 p1, P2 p2, P3 p3) {
    return AddInstruction(NewUncasted<I>(p1, p2, p3));
  }

  template<class I, class P1, class P2, class P3>
  I* Add(P1 p1, P2 p2, P3 p3) {
    return I::cast(AddUncasted<I>(p1, p2, p3));
  }

  template<class I, class P1, class P2, class P3, class P4>
  HInstruction* NewUncasted(P1 p1, P2 p2, P3 p3, P4 p4) {
    return I::New(zone(), context(), p1, p2, p3, p4);
  }

  template<class I, class P1, class P2, class P3, class P4>
  I* New(P1 p1, P2 p2, P3 p3, P4 p4) {
    return I::cast(NewUncasted<I>(p1, p2, p3, p4));
  }

  template<class I, class P1, class P2, class P3, class P4>
  HInstruction* AddUncasted(P1 p1, P2 p2, P3 p3, P4 p4) {
    return AddInstruction(NewUncasted<I>(p1, p2, p3, p4));
  }

  template<class I, class P1, class P2, class P3, class P4>
  I* Add(P1 p1, P2 p2, P3 p3, P4 p4) {
    return I::cast(AddUncasted<I>(p1, p2, p3, p4));
  }

  template<class I, class P1, class P2, class P3, class P4, class P5>
  HInstruction* NewUncasted(P1 p1, P2 p2, P3 p3, P4 p4, P5 p5) {
    return I::New(zone(), context(), p1, p2, p3, p4, p5);
  }

  template<class I, class P1, class P2, class P3, class P4, class P5>
  I* New(P1 p1, P2 p2, P3 p3, P4 p4, P5 p5) {
    return I::cast(NewUncasted<I>(p1, p2, p3, p4, p5));
  }

  template<class I, class P1, class P2, class P3, class P4, class P5>
  HInstruction* AddUncasted(P1 p1, P2 p2, P3 p3, P4 p4, P5 p5) {
    return AddInstruction(NewUncasted<I>(p1, p2, p3, p4, p5));
  }

  template<class I, class P1, class P2, class P3, class P4, class P5>
  I* Add(P1 p1, P2 p2, P3 p3, P4 p4, P5 p5) {
    return I::cast(AddUncasted<I>(p1, p2, p3, p4, p5));
  }

  template<class I, class P1, class P2, class P3, class P4, class P5, class P6>
  HInstruction* NewUncasted(P1 p1, P2 p2, P3 p3, P4 p4, P5 p5, P6 p6) {
    return I::New(zone(), context(), p1, p2, p3, p4, p5, p6);
  }

  template<class I, class P1, class P2, class P3, class P4, class P5, class P6>
  I* New(P1 p1, P2 p2, P3 p3, P4 p4, P5 p5, P6 p6) {
    return I::cast(NewUncasted<I>(p1, p2, p3, p4, p5, p6));
  }

  template<class I, class P1, class P2, class P3, class P4, class P5, class P6>
  HInstruction* AddUncasted(P1 p1, P2 p2, P3 p3, P4 p4, P5 p5, P6 p6) {
    return AddInstruction(NewUncasted<I>(p1, p2, p3, p4, p5, p6));
  }

  template<class I, class P1, class P2, class P3, class P4, class P5, class P6>
  I* Add(P1 p1, P2 p2, P3 p3, P4 p4, P5 p5, P6 p6) {
    return I::cast(AddInstruction(NewUncasted<I>(p1, p2, p3, p4, p5, p6)));
  }

  template<class I, class P1, class P2, class P3, class P4,
      class P5, class P6, class P7>
  HInstruction* NewUncasted(P1 p1, P2 p2, P3 p3, P4 p4, P5 p5, P6 p6, P7 p7) {
    return I::New(zone(), context(), p1, p2, p3, p4, p5, p6, p7);
  }

  template<class I, class P1, class P2, class P3, class P4,
      class P5, class P6, class P7>
      I* New(P1 p1, P2 p2, P3 p3, P4 p4, P5 p5, P6 p6, P7 p7) {
    return I::cast(NewUncasted<I>(p1, p2, p3, p4, p5, p6, p7));
  }

  template<class I, class P1, class P2, class P3,
           class P4, class P5, class P6, class P7>
  HInstruction* AddUncasted(P1 p1, P2 p2, P3 p3, P4 p4, P5 p5, P6 p6, P7 p7) {
    return AddInstruction(NewUncasted<I>(p1, p2, p3, p4, p5, p6, p7));
  }

  template<class I, class P1, class P2, class P3,
           class P4, class P5, class P6, class P7>
  I* Add(P1 p1, P2 p2, P3 p3, P4 p4, P5 p5, P6 p6, P7 p7) {
    return I::cast(AddInstruction(NewUncasted<I>(p1, p2, p3, p4,
                                                 p5, p6, p7)));
  }

  template<class I, class P1, class P2, class P3, class P4,
      class P5, class P6, class P7, class P8>
  HInstruction* NewUncasted(P1 p1, P2 p2, P3 p3, P4 p4,
                            P5 p5, P6 p6, P7 p7, P8 p8) {
    return I::New(zone(), context(), p1, p2, p3, p4, p5, p6, p7, p8);
  }

  template<class I, class P1, class P2, class P3, class P4,
      class P5, class P6, class P7, class P8>
      I* New(P1 p1, P2 p2, P3 p3, P4 p4, P5 p5, P6 p6, P7 p7, P8 p8) {
    return I::cast(NewUncasted<I>(p1, p2, p3, p4, p5, p6, p7, p8));
  }

  template<class I, class P1, class P2, class P3, class P4,
           class P5, class P6, class P7, class P8>
  HInstruction* AddUncasted(P1 p1, P2 p2, P3 p3, P4 p4,
                            P5 p5, P6 p6, P7 p7, P8 p8) {
    return AddInstruction(NewUncasted<I>(p1, p2, p3, p4, p5, p6, p7, p8));
  }

  template<class I, class P1, class P2, class P3, class P4,
           class P5, class P6, class P7, class P8>
  I* Add(P1 p1, P2 p2, P3 p3, P4 p4, P5 p5, P6 p6, P7 p7, P8 p8) {
    return I::cast(
        AddInstruction(NewUncasted<I>(p1, p2, p3, p4, p5, p6, p7, p8)));
  }

  void AddSimulate(BailoutId id, RemovableSimulate removable = FIXED_SIMULATE);

 protected:
  virtual bool BuildGraph() = 0;

  HBasicBlock* CreateBasicBlock(HEnvironment* env);
  HBasicBlock* CreateLoopHeaderBlock();

  HValue* BuildCheckHeapObject(HValue* object);
  HValue* BuildCheckMap(HValue* obj, Handle<Map> map);
  HValue* BuildWrapReceiver(HValue* object, HValue* function);

  // Building common constructs
  HValue* BuildCheckForCapacityGrow(HValue* object,
                                    HValue* elements,
                                    ElementsKind kind,
                                    HValue* length,
                                    HValue* key,
                                    bool is_js_array);

  HValue* BuildCopyElementsOnWrite(HValue* object,
                                   HValue* elements,
                                   ElementsKind kind,
                                   HValue* length);

  void BuildTransitionElementsKind(HValue* object,
                                   HValue* map,
                                   ElementsKind from_kind,
                                   ElementsKind to_kind,
                                   bool is_jsarray);

  HInstruction* BuildUncheckedMonomorphicElementAccess(
      HValue* checked_object,
      HValue* key,
      HValue* val,
      bool is_js_array,
      ElementsKind elements_kind,
      bool is_store,
      LoadKeyedHoleMode load_mode,
      KeyedAccessStoreMode store_mode);

  HInstruction* AddExternalArrayElementAccess(
      HValue* external_elements,
      HValue* checked_key,
      HValue* val,
      HValue* dependency,
      ElementsKind elements_kind,
      bool is_store);

  HInstruction* AddFastElementAccess(
      HValue* elements,
      HValue* checked_key,
      HValue* val,
      HValue* dependency,
      ElementsKind elements_kind,
      bool is_store,
      LoadKeyedHoleMode load_mode,
      KeyedAccessStoreMode store_mode);

  HLoadNamedField* BuildLoadNamedField(HValue* object, HObjectAccess access);
  HInstruction* BuildLoadStringLength(HValue* object, HValue* checked_value);
  HStoreNamedField* AddStoreMapConstant(HValue* object, Handle<Map>);
  HLoadNamedField* AddLoadElements(HValue* object);
  HLoadNamedField* AddLoadFixedArrayLength(HValue *object);

  HValue* AddLoadJSBuiltin(Builtins::JavaScript builtin);

  HValue* TruncateToNumber(HValue* value, Handle<Type>* expected);

  void PushAndAdd(HInstruction* instr);

  void FinishExitWithHardDeoptimization(const char* reason,
                                        HBasicBlock* continuation);

  void AddIncrementCounter(StatsCounter* counter,
                           HValue* context);

  class IfBuilder V8_FINAL {
   public:
    explicit IfBuilder(HGraphBuilder* builder,
                       int position = RelocInfo::kNoPosition);
    IfBuilder(HGraphBuilder* builder,
              HIfContinuation* continuation);

    ~IfBuilder() {
      if (!finished_) End();
    }

    template<class Condition>
    HInstruction* If(HValue *p) {
      HControlInstruction* compare = new(zone()) Condition(p);
      AddCompare(compare);
      return compare;
    }

    template<class Condition, class P2>
    HInstruction* If(HValue* p1, P2 p2) {
      HControlInstruction* compare = new(zone()) Condition(p1, p2);
      AddCompare(compare);
      return compare;
    }

    template<class Condition, class P2, class P3>
    HInstruction* If(HValue* p1, P2 p2, P3 p3) {
      HControlInstruction* compare = new(zone()) Condition(p1, p2, p3);
      AddCompare(compare);
      return compare;
    }

    template<class Condition, class P2>
    HInstruction* IfNot(HValue* p1, P2 p2) {
      HControlInstruction* compare = new(zone()) Condition(p1, p2);
      AddCompare(compare);
      HBasicBlock* block0 = compare->SuccessorAt(0);
      HBasicBlock* block1 = compare->SuccessorAt(1);
      compare->SetSuccessorAt(0, block1);
      compare->SetSuccessorAt(1, block0);
      return compare;
    }

    template<class Condition, class P2, class P3>
    HInstruction* IfNot(HValue* p1, P2 p2, P3 p3) {
      HControlInstruction* compare = new(zone()) Condition(p1, p2, p3);
      AddCompare(compare);
      HBasicBlock* block0 = compare->SuccessorAt(0);
      HBasicBlock* block1 = compare->SuccessorAt(1);
      compare->SetSuccessorAt(0, block1);
      compare->SetSuccessorAt(1, block0);
      return compare;
    }

    template<class Condition>
    HInstruction* OrIf(HValue *p) {
      Or();
      return If<Condition>(p);
    }

    template<class Condition, class P2>
    HInstruction* OrIf(HValue* p1, P2 p2) {
      Or();
      return If<Condition>(p1, p2);
    }

    template<class Condition, class P2, class P3>
    HInstruction* OrIf(HValue* p1, P2 p2, P3 p3) {
      Or();
      return If<Condition>(p1, p2, p3);
    }

    template<class Condition>
    HInstruction* AndIf(HValue *p) {
      And();
      return If<Condition>(p);
    }

    template<class Condition, class P2>
    HInstruction* AndIf(HValue* p1, P2 p2) {
      And();
      return If<Condition>(p1, p2);
    }

    template<class Condition, class P2, class P3>
    HInstruction* AndIf(HValue* p1, P2 p2, P3 p3) {
      And();
      return If<Condition>(p1, p2, p3);
    }

    void Or();
    void And();

    void CaptureContinuation(HIfContinuation* continuation);

    void Then();
    void Else();
    void End();

    void Deopt(const char* reason);
    void ElseDeopt(const char* reason) {
      Else();
      Deopt(reason);
    }

    void Return(HValue* value);

   private:
    void AddCompare(HControlInstruction* compare);

    Zone* zone() { return builder_->zone(); }

    HGraphBuilder* builder_;
    int position_;
    bool finished_ : 1;
    bool deopt_then_ : 1;
    bool deopt_else_ : 1;
    bool did_then_ : 1;
    bool did_else_ : 1;
    bool did_and_ : 1;
    bool did_or_ : 1;
    bool captured_ : 1;
    bool needs_compare_ : 1;
    HBasicBlock* first_true_block_;
    HBasicBlock* last_true_block_;
    HBasicBlock* first_false_block_;
    HBasicBlock* split_edge_merge_block_;
    HBasicBlock* merge_block_;
  };

  class LoopBuilder V8_FINAL {
   public:
    enum Direction {
      kPreIncrement,
      kPostIncrement,
      kPreDecrement,
      kPostDecrement
    };

    LoopBuilder(HGraphBuilder* builder,
                HValue* context,
                Direction direction);
    LoopBuilder(HGraphBuilder* builder,
                HValue* context,
                Direction direction,
                HValue* increment_amount);

    ~LoopBuilder() {
      ASSERT(finished_);
    }

    HValue* BeginBody(
        HValue* initial,
        HValue* terminating,
        Token::Value token);

    void Break();

    void EndBody();

   private:
    Zone* zone() { return builder_->zone(); }

    HGraphBuilder* builder_;
    HValue* context_;
    HValue* increment_amount_;
    HInstruction* increment_;
    HPhi* phi_;
    HBasicBlock* header_block_;
    HBasicBlock* body_block_;
    HBasicBlock* exit_block_;
    HBasicBlock* exit_trampoline_block_;
    Direction direction_;
    bool finished_;
  };

  HValue* BuildNewElementsCapacity(HValue* old_capacity);

  void BuildNewSpaceArrayCheck(HValue* length,
                               ElementsKind kind);

  class JSArrayBuilder V8_FINAL {
   public:
    JSArrayBuilder(HGraphBuilder* builder,
                   ElementsKind kind,
                   HValue* allocation_site_payload,
                   HValue* constructor_function,
                   AllocationSiteOverrideMode override_mode);

    JSArrayBuilder(HGraphBuilder* builder,
                   ElementsKind kind,
                   HValue* constructor_function);

    HValue* AllocateEmptyArray();
    HValue* AllocateArray(HValue* capacity, HValue* length_field,
                          bool fill_with_hole);
    HValue* GetElementsLocation() { return elements_location_; }

   private:
    Zone* zone() const { return builder_->zone(); }
    int elements_size() const {
      return IsFastDoubleElementsKind(kind_) ? kDoubleSize : kPointerSize;
    }
    HGraphBuilder* builder() { return builder_; }
    HGraph* graph() { return builder_->graph(); }
    int initial_capacity() {
      STATIC_ASSERT(JSArray::kPreallocatedArrayElements > 0);
      return JSArray::kPreallocatedArrayElements;
    }

    HValue* EmitMapCode();
    HValue* EmitInternalMapCode();
    HValue* EstablishEmptyArrayAllocationSize();
    HValue* EstablishAllocationSize(HValue* length_node);
    HValue* AllocateArray(HValue* size_in_bytes, HValue* capacity,
                          HValue* length_field,  bool fill_with_hole);

    HGraphBuilder* builder_;
    ElementsKind kind_;
    AllocationSiteMode mode_;
    HValue* allocation_site_payload_;
    HValue* constructor_function_;
    HInnerAllocatedObject* elements_location_;
  };

  HValue* BuildAllocateElements(ElementsKind kind,
                                HValue* capacity);

  void BuildInitializeElementsHeader(HValue* elements,
                                     ElementsKind kind,
                                     HValue* capacity);

  HValue* BuildAllocateElementsAndInitializeElementsHeader(ElementsKind kind,
                                                           HValue* capacity);

  // array must have been allocated with enough room for
  // 1) the JSArray, 2) a AllocationMemento if mode requires it,
  // 3) a FixedArray or FixedDoubleArray.
  // A pointer to the Fixed(Double)Array is returned.
  HInnerAllocatedObject* BuildJSArrayHeader(HValue* array,
                                            HValue* array_map,
                                            AllocationSiteMode mode,
                                            ElementsKind elements_kind,
                                            HValue* allocation_site_payload,
                                            HValue* length_field);

  HValue* BuildGrowElementsCapacity(HValue* object,
                                    HValue* elements,
                                    ElementsKind kind,
                                    ElementsKind new_kind,
                                    HValue* length,
                                    HValue* new_capacity);

  void BuildFillElementsWithHole(HValue* elements,
                                 ElementsKind elements_kind,
                                 HValue* from,
                                 HValue* to);

  void BuildCopyElements(HValue* from_elements,
                         ElementsKind from_elements_kind,
                         HValue* to_elements,
                         ElementsKind to_elements_kind,
                         HValue* length,
                         HValue* capacity);

  HValue* BuildCloneShallowArray(HValue* boilerplate,
                                 HValue* allocation_site,
                                 AllocationSiteMode mode,
                                 ElementsKind kind,
                                 int length);

  void BuildCompareNil(
      HValue* value,
      Handle<Type> type,
      int position,
      HIfContinuation* continuation);

  HValue* BuildCreateAllocationMemento(HValue* previous_object,
                                       int previous_object_size,
                                       HValue* payload);

  HInstruction* BuildConstantMapCheck(Handle<JSObject> constant,
                                      CompilationInfo* info);
  HInstruction* BuildCheckPrototypeMaps(Handle<JSObject> prototype,
                                        Handle<JSObject> holder);

  HInstruction* BuildGetNativeContext();
  HInstruction* BuildGetArrayFunction();

 private:
  HGraphBuilder();

  void PadEnvironmentForContinuation(HBasicBlock* from,
                                     HBasicBlock* continuation);

  CompilationInfo* info_;
  HGraph* graph_;
  HBasicBlock* current_block_;
};


template<>
inline HInstruction* HGraphBuilder::AddUncasted<HDeoptimize>(
    const char* reason, Deoptimizer::BailoutType type) {
  if (type == Deoptimizer::SOFT) {
    isolate()->counters()->soft_deopts_requested()->Increment();
    if (FLAG_always_opt) return NULL;
  }
  if (current_block()->IsDeoptimizing()) return NULL;
  HDeoptimize* instr = New<HDeoptimize>(reason, type);
  AddInstruction(instr);
  if (type == Deoptimizer::SOFT) {
    isolate()->counters()->soft_deopts_inserted()->Increment();
    graph()->set_has_soft_deoptimize(true);
  }
  current_block()->MarkAsDeoptimizing();
  return instr;
}


template<>
inline HDeoptimize* HGraphBuilder::Add<HDeoptimize>(
    const char* reason, Deoptimizer::BailoutType type) {
  return static_cast<HDeoptimize*>(AddUncasted<HDeoptimize>(reason, type));
}


template<>
inline HInstruction* HGraphBuilder::AddUncasted<HSimulate>(
    BailoutId id,
    RemovableSimulate removable) {
  HSimulate* instr = current_block()->CreateSimulate(id, removable);
  AddInstruction(instr);
  return instr;
}


template<>
inline HInstruction* HGraphBuilder::AddUncasted<HSimulate>(BailoutId id) {
  return AddUncasted<HSimulate>(id, FIXED_SIMULATE);
}


template<>
inline HInstruction* HGraphBuilder::AddUncasted<HReturn>(HValue* value) {
  int num_parameters = graph()->info()->num_parameters();
  HValue* params = AddUncasted<HConstant>(num_parameters);
  HReturn* return_instruction = New<HReturn>(value, params);
  current_block()->FinishExit(return_instruction);
  return return_instruction;
}


template<>
inline HInstruction* HGraphBuilder::AddUncasted<HReturn>(HConstant* value) {
  return AddUncasted<HReturn>(static_cast<HValue*>(value));
}


template<>
inline HInstruction* HGraphBuilder::NewUncasted<HContext>() {
  return HContext::New(zone());
}


class HOptimizedGraphBuilder V8_FINAL
    : public HGraphBuilder, public AstVisitor {
 public:
  // A class encapsulating (lazily-allocated) break and continue blocks for
  // a breakable statement.  Separated from BreakAndContinueScope so that it
  // can have a separate lifetime.
  class BreakAndContinueInfo V8_FINAL BASE_EMBEDDED {
   public:
    explicit BreakAndContinueInfo(BreakableStatement* target,
                                  int drop_extra = 0)
        : target_(target),
          break_block_(NULL),
          continue_block_(NULL),
          drop_extra_(drop_extra) {
    }

    BreakableStatement* target() { return target_; }
    HBasicBlock* break_block() { return break_block_; }
    void set_break_block(HBasicBlock* block) { break_block_ = block; }
    HBasicBlock* continue_block() { return continue_block_; }
    void set_continue_block(HBasicBlock* block) { continue_block_ = block; }
    int drop_extra() { return drop_extra_; }

   private:
    BreakableStatement* target_;
    HBasicBlock* break_block_;
    HBasicBlock* continue_block_;
    int drop_extra_;
  };

  // A helper class to maintain a stack of current BreakAndContinueInfo
  // structures mirroring BreakableStatement nesting.
  class BreakAndContinueScope V8_FINAL BASE_EMBEDDED {
   public:
    BreakAndContinueScope(BreakAndContinueInfo* info,
                          HOptimizedGraphBuilder* owner)
        : info_(info), owner_(owner), next_(owner->break_scope()) {
      owner->set_break_scope(this);
    }

    ~BreakAndContinueScope() { owner_->set_break_scope(next_); }

    BreakAndContinueInfo* info() { return info_; }
    HOptimizedGraphBuilder* owner() { return owner_; }
    BreakAndContinueScope* next() { return next_; }

    // Search the break stack for a break or continue target.
    enum BreakType { BREAK, CONTINUE };
    HBasicBlock* Get(BreakableStatement* stmt, BreakType type, int* drop_extra);

   private:
    BreakAndContinueInfo* info_;
    HOptimizedGraphBuilder* owner_;
    BreakAndContinueScope* next_;
  };

  explicit HOptimizedGraphBuilder(CompilationInfo* info);

  virtual bool BuildGraph() V8_OVERRIDE;

  // Simple accessors.
  BreakAndContinueScope* break_scope() const { return break_scope_; }
  void set_break_scope(BreakAndContinueScope* head) { break_scope_ = head; }

  bool inline_bailout() { return inline_bailout_; }

  HValue* context() { return environment()->context(); }

  void Bailout(BailoutReason reason);

  HBasicBlock* CreateJoin(HBasicBlock* first,
                          HBasicBlock* second,
                          BailoutId join_id);

  FunctionState* function_state() const { return function_state_; }

  void VisitDeclarations(ZoneList<Declaration*>* declarations);

  void* operator new(size_t size, Zone* zone) {
    return zone->New(static_cast<int>(size));
  }
  void operator delete(void* pointer, Zone* zone) { }
  void operator delete(void* pointer) { }

  DEFINE_AST_VISITOR_SUBCLASS_MEMBERS();

 private:
  // Type of a member function that generates inline code for a native function.
  typedef void (HOptimizedGraphBuilder::*InlineFunctionGenerator)
      (CallRuntime* call);

  // Forward declarations for inner scope classes.
  class SubgraphScope;

  static const InlineFunctionGenerator kInlineFunctionGenerators[];

  static const int kMaxCallPolymorphism = 4;
  static const int kMaxLoadPolymorphism = 4;
  static const int kMaxStorePolymorphism = 4;

  // Even in the 'unlimited' case we have to have some limit in order not to
  // overflow the stack.
  static const int kUnlimitedMaxInlinedSourceSize = 100000;
  static const int kUnlimitedMaxInlinedNodes = 10000;
  static const int kUnlimitedMaxInlinedNodesCumulative = 10000;

  // Maximum depth and total number of elements and properties for literal
  // graphs to be considered for fast deep-copying.
  static const int kMaxFastLiteralDepth = 3;
  static const int kMaxFastLiteralProperties = 8;

  // Simple accessors.
  void set_function_state(FunctionState* state) { function_state_ = state; }

  AstContext* ast_context() const { return ast_context_; }
  void set_ast_context(AstContext* context) { ast_context_ = context; }

  // Accessors forwarded to the function state.
  CompilationInfo* current_info() const {
    return function_state()->compilation_info();
  }
  AstContext* call_context() const {
    return function_state()->call_context();
  }
  HBasicBlock* function_return() const {
    return function_state()->function_return();
  }
  TestContext* inlined_test_context() const {
    return function_state()->test_context();
  }
  void ClearInlinedTestContext() {
    function_state()->ClearInlinedTestContext();
  }
  StrictModeFlag function_strict_mode_flag() {
    return function_state()->compilation_info()->is_classic_mode()
        ? kNonStrictMode : kStrictMode;
  }

  // Generators for inline runtime functions.
#define INLINE_FUNCTION_GENERATOR_DECLARATION(Name, argc, ressize)      \
  void Generate##Name(CallRuntime* call);

  INLINE_FUNCTION_LIST(INLINE_FUNCTION_GENERATOR_DECLARATION)
  INLINE_RUNTIME_FUNCTION_LIST(INLINE_FUNCTION_GENERATOR_DECLARATION)
#undef INLINE_FUNCTION_GENERATOR_DECLARATION

  void VisitDelete(UnaryOperation* expr);
  void VisitVoid(UnaryOperation* expr);
  void VisitTypeof(UnaryOperation* expr);
  void VisitNot(UnaryOperation* expr);

  void VisitComma(BinaryOperation* expr);
  void VisitLogicalExpression(BinaryOperation* expr);
  void VisitArithmeticExpression(BinaryOperation* expr);

  bool PreProcessOsrEntry(IterationStatement* statement);
  void VisitLoopBody(IterationStatement* stmt,
                     HBasicBlock* loop_entry,
                     BreakAndContinueInfo* break_info);

  // Create a back edge in the flow graph.  body_exit is the predecessor
  // block and loop_entry is the successor block.  loop_successor is the
  // block where control flow exits the loop normally (e.g., via failure of
  // the condition) and break_block is the block where control flow breaks
  // from the loop.  All blocks except loop_entry can be NULL.  The return
  // value is the new successor block which is the join of loop_successor
  // and break_block, or NULL.
  HBasicBlock* CreateLoop(IterationStatement* statement,
                          HBasicBlock* loop_entry,
                          HBasicBlock* body_exit,
                          HBasicBlock* loop_successor,
                          HBasicBlock* break_block);

  HBasicBlock* JoinContinue(IterationStatement* statement,
                            HBasicBlock* exit_block,
                            HBasicBlock* continue_block);

  HValue* Top() const { return environment()->Top(); }
  void Drop(int n) { environment()->Drop(n); }
  void Bind(Variable* var, HValue* value) { environment()->Bind(var, value); }
  bool IsEligibleForEnvironmentLivenessAnalysis(Variable* var,
                                                int index,
                                                HValue* value,
                                                HEnvironment* env) {
    if (!FLAG_analyze_environment_liveness) return false;
    // |this| and |arguments| are always live; zapping parameters isn't
    // safe because function.arguments can inspect them at any time.
    return !var->is_this() &&
           !var->is_arguments() &&
           !value->IsArgumentsObject() &&
           env->is_local_index(index);
  }
  void BindIfLive(Variable* var, HValue* value) {
    HEnvironment* env = environment();
    int index = env->IndexFor(var);
    env->Bind(index, value);
    if (IsEligibleForEnvironmentLivenessAnalysis(var, index, value, env)) {
      HEnvironmentMarker* bind =
          new(zone()) HEnvironmentMarker(HEnvironmentMarker::BIND, index);
      AddInstruction(bind);
#ifdef DEBUG
      bind->set_closure(env->closure());
#endif
    }
  }
  HValue* LookupAndMakeLive(Variable* var) {
    HEnvironment* env = environment();
    int index = env->IndexFor(var);
    HValue* value = env->Lookup(index);
    if (IsEligibleForEnvironmentLivenessAnalysis(var, index, value, env)) {
      HEnvironmentMarker* lookup =
          new(zone()) HEnvironmentMarker(HEnvironmentMarker::LOOKUP, index);
      AddInstruction(lookup);
#ifdef DEBUG
      lookup->set_closure(env->closure());
#endif
    }
    return value;
  }

  // The value of the arguments object is allowed in some but not most value
  // contexts.  (It's allowed in all effect contexts and disallowed in all
  // test contexts.)
  void VisitForValue(Expression* expr,
                     ArgumentsAllowedFlag flag = ARGUMENTS_NOT_ALLOWED);
  void VisitForTypeOf(Expression* expr);
  void VisitForEffect(Expression* expr);
  void VisitForControl(Expression* expr,
                       HBasicBlock* true_block,
                       HBasicBlock* false_block);

  // Visit an argument subexpression and emit a push to the outgoing arguments.
  void VisitArgument(Expression* expr);

  void VisitArgumentList(ZoneList<Expression*>* arguments);

  // Visit a list of expressions from left to right, each in a value context.
  void VisitExpressions(ZoneList<Expression*>* exprs);

  // Remove the arguments from the bailout environment and emit instructions
  // to push them as outgoing parameters.
  template <class Instruction> HInstruction* PreProcessCall(Instruction* call);

  void SetUpScope(Scope* scope);
  virtual void VisitStatements(ZoneList<Statement*>* statements) V8_OVERRIDE;

#define DECLARE_VISIT(type) virtual void Visit##type(type* node) V8_OVERRIDE;
  AST_NODE_LIST(DECLARE_VISIT)
#undef DECLARE_VISIT

  // Helpers for flow graph construction.
  enum GlobalPropertyAccess {
    kUseCell,
    kUseGeneric
  };
  GlobalPropertyAccess LookupGlobalProperty(Variable* var,
                                            LookupResult* lookup,
                                            bool is_store);

  void EnsureArgumentsArePushedForAccess();
  bool TryArgumentsAccess(Property* expr);

  // Try to optimize fun.apply(receiver, arguments) pattern.
  bool TryCallApply(Call* expr);

  int InliningAstSize(Handle<JSFunction> target);
  bool TryInline(CallKind call_kind,
                 Handle<JSFunction> target,
                 int arguments_count,
                 HValue* implicit_return_value,
                 BailoutId ast_id,
                 BailoutId return_id,
                 InliningKind inlining_kind);

  bool TryInlineCall(Call* expr, bool drop_extra = false);
  bool TryInlineConstruct(CallNew* expr, HValue* implicit_return_value);
  bool TryInlineGetter(Handle<JSFunction> getter,
                       BailoutId ast_id,
                       BailoutId return_id);
  bool TryInlineSetter(Handle<JSFunction> setter,
                       BailoutId id,
                       BailoutId assignment_id,
                       HValue* implicit_return_value);
  bool TryInlineApply(Handle<JSFunction> function,
                      Call* expr,
                      int arguments_count);
  bool TryInlineBuiltinMethodCall(Call* expr,
                                  HValue* receiver,
                                  Handle<Map> receiver_map,
                                  CheckType check_type);
  bool TryInlineBuiltinFunctionCall(Call* expr, bool drop_extra);

  // If --trace-inlining, print a line of the inlining trace.  Inlining
  // succeeded if the reason string is NULL and failed if there is a
  // non-NULL reason string.
  void TraceInline(Handle<JSFunction> target,
                   Handle<JSFunction> caller,
                   const char* failure_reason);

  void HandleGlobalVariableAssignment(Variable* var,
                                      HValue* value,
                                      int position,
                                      BailoutId ast_id);

  void HandlePropertyAssignment(Assignment* expr);
  void HandleCompoundAssignment(Assignment* expr);
  void HandlePolymorphicLoadNamedField(int position,
                                       BailoutId return_id,
                                       HValue* object,
                                       SmallMapList* types,
                                       Handle<String> name);
  HInstruction* TryLoadPolymorphicAsMonomorphic(HValue* object,
                                                SmallMapList* types,
                                                Handle<String> name);
  void HandlePolymorphicStoreNamedField(int position,
                                        BailoutId assignment_id,
                                        HValue* object,
                                        HValue* value,
                                        SmallMapList* types,
                                        Handle<String> name);
  bool TryStorePolymorphicAsMonomorphic(int position,
                                        BailoutId assignment_id,
                                        HValue* object,
                                        HValue* value,
                                        SmallMapList* types,
                                        Handle<String> name);
  void HandlePolymorphicCallNamed(Call* expr,
                                  HValue* receiver,
                                  SmallMapList* types,
                                  Handle<String> name);
  bool TryCallPolymorphicAsMonomorphic(Call* expr,
                                       HValue* receiver,
                                       SmallMapList* types,
                                       Handle<String> name);
  void HandleLiteralCompareTypeof(CompareOperation* expr,
                                  Expression* sub_expr,
                                  Handle<String> check);
  void HandleLiteralCompareNil(CompareOperation* expr,
                               Expression* sub_expr,
                               NilValue nil);

  HInstruction* BuildStringCharCodeAt(HValue* string,
                                      HValue* index);
  HInstruction* BuildBinaryOperation(BinaryOperation* expr,
                                     HValue* left,
                                     HValue* right);
  HInstruction* BuildIncrement(bool returns_original_input,
                               CountOperation* expr);
  HInstruction* BuildLoadKeyedGeneric(HValue* object,
                                      HValue* key);

  HInstruction* TryBuildConsolidatedElementLoad(HValue* object,
                                                HValue* key,
                                                HValue* val,
                                                SmallMapList* maps);

  LoadKeyedHoleMode BuildKeyedHoleMode(Handle<Map> map);

  HInstruction* BuildMonomorphicElementAccess(HValue* object,
                                              HValue* key,
                                              HValue* val,
                                              HValue* dependency,
                                              Handle<Map> map,
                                              bool is_store,
                                              KeyedAccessStoreMode store_mode);

  HValue* HandlePolymorphicElementAccess(HValue* object,
                                         HValue* key,
                                         HValue* val,
                                         Expression* prop,
                                         BailoutId ast_id,
                                         int position,
                                         bool is_store,
                                         KeyedAccessStoreMode store_mode,
                                         bool* has_side_effects);

  HValue* HandleKeyedElementAccess(HValue* obj,
                                   HValue* key,
                                   HValue* val,
                                   Expression* expr,
                                   BailoutId ast_id,
                                   int position,
                                   bool is_store,
                                   bool* has_side_effects);

  HInstruction* BuildLoadNamedGeneric(HValue* object,
                                      Handle<String> name,
                                      Property* expr);
  HInstruction* BuildCallGetter(HValue* object,
                                Handle<Map> map,
                                Handle<JSFunction> getter,
                                Handle<JSObject> holder);
  HInstruction* BuildLoadNamedMonomorphic(HValue* object,
                                          Handle<String> name,
                                          Handle<Map> map);

  HCheckMaps* AddCheckMap(HValue* object, Handle<Map> map);

  void BuildLoad(Property* property,
                 int position,
                 BailoutId ast_id);
  void PushLoad(Property* property,
                HValue* object,
                HValue* key,
                int position);

  void BuildStoreForEffect(Expression* expression,
                           Property* prop,
                           BailoutId ast_id,
                           BailoutId return_id,
                           HValue* object,
                           HValue* key,
                           HValue* value);

  void BuildStore(Expression* expression,
                  Property* prop,
                  BailoutId ast_id,
                  BailoutId return_id,
                  bool is_uninitialized = false);

  HInstruction* BuildStoreNamedField(HValue* object,
                                     Handle<String> name,
                                     HValue* value,
                                     Handle<Map> map,
                                     LookupResult* lookup);
  HInstruction* BuildStoreNamedGeneric(HValue* object,
                                       Handle<String> name,
                                       HValue* value);
  HInstruction* BuildStoreNamedMonomorphic(HValue* object,
                                           Handle<String> name,
                                           HValue* value,
                                           Handle<Map> map);
  HInstruction* BuildStoreKeyedGeneric(HValue* object,
                                       HValue* key,
                                       HValue* value);

  HValue* BuildContextChainWalk(Variable* var);

  HInstruction* BuildThisFunction();

  HInstruction* BuildFastLiteral(Handle<JSObject> boilerplate_object,
                                 Handle<Object> allocation_site,
                                 AllocationSiteMode mode);

  void BuildEmitObjectHeader(Handle<JSObject> boilerplate_object,
                             HInstruction* object);

  void BuildInitElementsInObjectHeader(Handle<JSObject> boilerplate_object,
                                       HInstruction* object,
                                       HInstruction* object_elements);

  void BuildEmitInObjectProperties(Handle<JSObject> boilerplate_object,
                                   HInstruction* object);

  void BuildEmitElements(Handle<JSObject> boilerplate_object,
                         Handle<FixedArrayBase> elements,
                         HValue* object_elements);

  void BuildEmitFixedDoubleArray(Handle<FixedArrayBase> elements,
                                 ElementsKind kind,
                                 HValue* object_elements);

  void BuildEmitFixedArray(Handle<FixedArrayBase> elements,
                           ElementsKind kind,
                           HValue* object_elements);

  void AddCheckPrototypeMaps(Handle<JSObject> holder,
                             Handle<Map> receiver_map);

  void AddCheckConstantFunction(Handle<JSObject> holder,
                                HValue* receiver,
                                Handle<Map> receiver_map);

  bool MatchRotateRight(HValue* left,
                        HValue* right,
                        HValue** operand,
                        HValue** shift_amount);

  // The translation state of the currently-being-translated function.
  FunctionState* function_state_;

  // The base of the function state stack.
  FunctionState initial_function_state_;

  // Expression context of the currently visited subexpression. NULL when
  // visiting statements.
  AstContext* ast_context_;

  // A stack of breakable statements entered.
  BreakAndContinueScope* break_scope_;

  int inlined_count_;
  ZoneList<Handle<Object> > globals_;

  bool inline_bailout_;

  HOsrBuilder* osr_;

  friend class FunctionState;  // Pushes and pops the state stack.
  friend class AstContext;  // Pushes and pops the AST context stack.
  friend class KeyedLoadFastElementStub;
  friend class HOsrBuilder;

  DISALLOW_COPY_AND_ASSIGN(HOptimizedGraphBuilder);
};


Zone* AstContext::zone() const { return owner_->zone(); }


class HStatistics V8_FINAL: public Malloced {
 public:
  HStatistics()
      : times_(5),
        names_(5),
        sizes_(5),
        total_size_(0),
        source_size_(0) { }

  void Initialize(CompilationInfo* info);
  void Print();
  void SaveTiming(const char* name, TimeDelta time, unsigned size);

  void IncrementFullCodeGen(TimeDelta full_code_gen) {
    full_code_gen_ += full_code_gen;
  }

  void IncrementSubtotals(TimeDelta create_graph,
                          TimeDelta optimize_graph,
                          TimeDelta generate_code) {
    create_graph_ += create_graph;
    optimize_graph_ += optimize_graph;
    generate_code_ += generate_code;
  }

 private:
  List<TimeDelta> times_;
  List<const char*> names_;
  List<unsigned> sizes_;
  TimeDelta create_graph_;
  TimeDelta optimize_graph_;
  TimeDelta generate_code_;
  unsigned total_size_;
  TimeDelta full_code_gen_;
  double source_size_;
};


class HPhase : public CompilationPhase {
 public:
  HPhase(const char* name, HGraph* graph)
      : CompilationPhase(name, graph->info()),
        graph_(graph) { }
  ~HPhase();

 protected:
  HGraph* graph() const { return graph_; }

 private:
  HGraph* graph_;

  DISALLOW_COPY_AND_ASSIGN(HPhase);
};


class HTracer V8_FINAL : public Malloced {
 public:
  explicit HTracer(int isolate_id)
      : trace_(&string_allocator_), indent_(0) {
    if (FLAG_trace_hydrogen_file == NULL) {
      OS::SNPrintF(filename_,
                   "hydrogen-%d-%d.cfg",
                   OS::GetCurrentProcessId(),
                   isolate_id);
    } else {
      OS::StrNCpy(filename_, FLAG_trace_hydrogen_file, filename_.length());
    }
    WriteChars(filename_.start(), "", 0, false);
  }

  void TraceCompilation(CompilationInfo* info);
  void TraceHydrogen(const char* name, HGraph* graph);
  void TraceLithium(const char* name, LChunk* chunk);
  void TraceLiveRanges(const char* name, LAllocator* allocator);

 private:
  class Tag V8_FINAL BASE_EMBEDDED {
   public:
    Tag(HTracer* tracer, const char* name) {
      name_ = name;
      tracer_ = tracer;
      tracer->PrintIndent();
      tracer->trace_.Add("begin_%s\n", name);
      tracer->indent_++;
    }

    ~Tag() {
      tracer_->indent_--;
      tracer_->PrintIndent();
      tracer_->trace_.Add("end_%s\n", name_);
      ASSERT(tracer_->indent_ >= 0);
      tracer_->FlushToFile();
    }

   private:
    HTracer* tracer_;
    const char* name_;
  };

  void TraceLiveRange(LiveRange* range, const char* type, Zone* zone);
  void Trace(const char* name, HGraph* graph, LChunk* chunk);
  void FlushToFile();

  void PrintEmptyProperty(const char* name) {
    PrintIndent();
    trace_.Add("%s\n", name);
  }

  void PrintStringProperty(const char* name, const char* value) {
    PrintIndent();
    trace_.Add("%s \"%s\"\n", name, value);
  }

  void PrintLongProperty(const char* name, int64_t value) {
    PrintIndent();
    trace_.Add("%s %d000\n", name, static_cast<int>(value / 1000));
  }

  void PrintBlockProperty(const char* name, int block_id) {
    PrintIndent();
    trace_.Add("%s \"B%d\"\n", name, block_id);
  }

  void PrintIntProperty(const char* name, int value) {
    PrintIndent();
    trace_.Add("%s %d\n", name, value);
  }

  void PrintIndent() {
    for (int i = 0; i < indent_; i++) {
      trace_.Add("  ");
    }
  }

  EmbeddedVector<char, 64> filename_;
  HeapStringAllocator string_allocator_;
  StringStream trace_;
  int indent_;
};


class NoObservableSideEffectsScope V8_FINAL {
 public:
  explicit NoObservableSideEffectsScope(HGraphBuilder* builder) :
      builder_(builder) {
    builder_->graph()->IncrementInNoSideEffectsScope();
  }
  ~NoObservableSideEffectsScope() {
    builder_->graph()->DecrementInNoSideEffectsScope();
  }

 private:
  HGraphBuilder* builder_;
};


} }  // namespace v8::internal

#endif  // V8_HYDROGEN_H_