src/interpreter/bytecode-generator.cc

// Copyright 2015 the V8 project authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#include "src/interpreter/bytecode-generator.h"

#include "src/ast/scopes.h"
#include "src/compiler.h"
#include "src/interpreter/control-flow-builders.h"
#include "src/objects.h"
#include "src/parsing/parser.h"
#include "src/parsing/token.h"

namespace v8 {
namespace internal {
namespace interpreter {


// Scoped class tracking context objects created by the visitor. Represents
// mutations of the context chain within the function body, allowing pushing and
// popping of the current {context_register} during visitation.
class BytecodeGenerator::ContextScope BASE_EMBEDDED {
 public:
  ContextScope(BytecodeGenerator* generator, Scope* scope,
               bool should_pop_context = true)
      : generator_(generator),
        scope_(scope),
        outer_(generator_->execution_context()),
        register_(generator_->NextContextRegister()),
        depth_(0),
        should_pop_context_(should_pop_context) {
    if (outer_) {
      depth_ = outer_->depth_ + 1;
      generator_->builder()->PushContext(register_);
    }
    generator_->set_execution_context(this);
  }

  ~ContextScope() {
    if (outer_ && should_pop_context_) {
      generator_->builder()->PopContext(outer_->reg());
    }
    generator_->set_execution_context(outer_);
  }

  // Returns the depth of the given |scope| for the current execution context.
  int ContextChainDepth(Scope* scope) {
    return scope_->ContextChainLength(scope);
  }

  // Returns the execution context at |depth| in the current context chain if it
  // is a function local execution context, otherwise returns nullptr.
  ContextScope* Previous(int depth) {
    if (depth > depth_) {
      return nullptr;
    }

    ContextScope* previous = this;
    for (int i = depth; i > 0; --i) {
      previous = previous->outer_;
    }
    return previous;
  }

  Scope* scope() const { return scope_; }
  Register reg() const { return register_; }

 private:
  BytecodeGenerator* generator_;
  Scope* scope_;
  ContextScope* outer_;
  Register register_;
  int depth_;
  bool should_pop_context_;
};


// Scoped class for tracking control statements entered by the
// visitor. The pattern derives AstGraphBuilder::ControlScope.
class BytecodeGenerator::ControlScope BASE_EMBEDDED {
 public:
  explicit ControlScope(BytecodeGenerator* generator)
      : generator_(generator), outer_(generator->execution_control()) {
    generator_->set_execution_control(this);
  }
  virtual ~ControlScope() { generator_->set_execution_control(outer()); }

  void Break(Statement* stmt) { PerformCommand(CMD_BREAK, stmt); }
  void Continue(Statement* stmt) { PerformCommand(CMD_CONTINUE, stmt); }

 protected:
  enum Command { CMD_BREAK, CMD_CONTINUE };
  void PerformCommand(Command command, Statement* statement);
  virtual bool Execute(Command command, Statement* statement) = 0;

  BytecodeGenerator* generator() const { return generator_; }
  ControlScope* outer() const { return outer_; }

 private:
  BytecodeGenerator* generator_;
  ControlScope* outer_;

  DISALLOW_COPY_AND_ASSIGN(ControlScope);
};


// Scoped class for enabling break inside blocks and switch blocks.
class BytecodeGenerator::ControlScopeForBreakable final
    : public BytecodeGenerator::ControlScope {
 public:
  ControlScopeForBreakable(BytecodeGenerator* generator,
                           BreakableStatement* statement,
                           BreakableControlFlowBuilder* control_builder)
      : ControlScope(generator),
        statement_(statement),
        control_builder_(control_builder) {}

 protected:
  virtual bool Execute(Command command, Statement* statement) {
    if (statement != statement_) return false;
    switch (command) {
      case CMD_BREAK:
        control_builder_->Break();
        return true;
      case CMD_CONTINUE:
        break;
    }
    return false;
  }

 private:
  Statement* statement_;
  BreakableControlFlowBuilder* control_builder_;
};


// Scoped class for enabling 'break' and 'continue' in iteration
// constructs, e.g. do...while, while..., for...
class BytecodeGenerator::ControlScopeForIteration final
    : public BytecodeGenerator::ControlScope {
 public:
  ControlScopeForIteration(BytecodeGenerator* generator,
                           IterationStatement* statement,
                           LoopBuilder* loop_builder)
      : ControlScope(generator),
        statement_(statement),
        loop_builder_(loop_builder) {}

 protected:
  virtual bool Execute(Command command, Statement* statement) {
    if (statement != statement_) return false;
    switch (command) {
      case CMD_BREAK:
        loop_builder_->Break();
        return true;
      case CMD_CONTINUE:
        loop_builder_->Continue();
        return true;
    }
    return false;
  }

 private:
  Statement* statement_;
  LoopBuilder* loop_builder_;
};


void BytecodeGenerator::ControlScope::PerformCommand(Command command,
                                                     Statement* statement) {
  ControlScope* current = this;
  do {
    if (current->Execute(command, statement)) return;
    current = current->outer();
  } while (current != nullptr);
  UNREACHABLE();
}


// Scoped base class for determining where the result of an expression
// is stored.
class BytecodeGenerator::ExpressionResultScope {
 public:
  ExpressionResultScope(BytecodeGenerator* generator, Expression::Context kind)
      : generator_(generator),
        kind_(kind),
        outer_(generator->execution_result()),
        allocator_(builder()),
        result_identified_(false) {
    generator_->set_execution_result(this);
  }

  virtual ~ExpressionResultScope() {
    generator_->set_execution_result(outer_);
    DCHECK(result_identified());
  }

  bool IsEffect() const { return kind_ == Expression::kEffect; }
  bool IsValue() const { return kind_ == Expression::kValue; }

  virtual void SetResultInAccumulator() = 0;
  virtual void SetResultInRegister(Register reg) = 0;

  BytecodeGenerator* generator() const { return generator_; }
  BytecodeArrayBuilder* builder() const { return generator()->builder(); }
  ExpressionResultScope* outer() const { return outer_; }

  Register NewRegister() {
    ExpressionResultScope* current_scope = generator()->execution_result();
    if ((current_scope == this) ||
        (current_scope->outer() == this &&
         !current_scope->allocator_.hasConsecutiveAllocations())) {
      // Regular case - Allocating registers in current or outer context.
      // VisitForRegisterValue allocates register in outer context.
      return allocator_.NewRegister();
    } else {
      // We need this when allocating registers due to an Assignment hazard.
      // It might be expensive to walk the full context chain and compute the
      // list of consecutive reservations in the innerscopes. So allocates a
      // new unallocated temporary register.
      return allocator_.AllocateNewRegister();
    }
  }

  void PrepareForConsecutiveAllocations(size_t count) {
    allocator_.PrepareForConsecutiveAllocations(count);
  }

  Register NextConsecutiveRegister() {
    return allocator_.NextConsecutiveRegister();
  }

 protected:
  void set_result_identified() {
    DCHECK(!result_identified());
    result_identified_ = true;
  }

  bool result_identified() const { return result_identified_; }

  const TemporaryRegisterScope* allocator() const { return &allocator_; }

 private:
  BytecodeGenerator* generator_;
  Expression::Context kind_;
  ExpressionResultScope* outer_;
  TemporaryRegisterScope allocator_;
  bool result_identified_;

  DISALLOW_COPY_AND_ASSIGN(ExpressionResultScope);
};


// Scoped class used when the result of the current expression is not
// expected to produce a result.
class BytecodeGenerator::EffectResultScope final
    : public ExpressionResultScope {
 public:
  explicit EffectResultScope(BytecodeGenerator* generator)
      : ExpressionResultScope(generator, Expression::kEffect) {
    set_result_identified();
  }

  virtual void SetResultInAccumulator() {}
  virtual void SetResultInRegister(Register reg) {}
};


// Scoped class used when the result of the current expression to be
// evaluated should go into the interpreter's accumulator register.
class BytecodeGenerator::AccumulatorResultScope final
    : public ExpressionResultScope {
 public:
  explicit AccumulatorResultScope(BytecodeGenerator* generator)
      : ExpressionResultScope(generator, Expression::kValue) {}

  virtual void SetResultInAccumulator() { set_result_identified(); }

  virtual void SetResultInRegister(Register reg) {
    builder()->LoadAccumulatorWithRegister(reg);
    set_result_identified();
  }
};


// Scoped class used when the result of the current expression to be
// evaluated should go into an interpreter register.
class BytecodeGenerator::RegisterResultScope final
    : public ExpressionResultScope {
 public:
  explicit RegisterResultScope(BytecodeGenerator* generator)
      : ExpressionResultScope(generator, Expression::kValue) {}

  virtual void SetResultInAccumulator() {
    result_register_ = outer()->NewRegister();
    builder()->StoreAccumulatorInRegister(result_register_);
    set_result_identified();
  }

  virtual void SetResultInRegister(Register reg) {
    DCHECK(builder()->RegisterIsParameterOrLocal(reg) ||
           (builder()->RegisterIsTemporary(reg) &&
            !allocator()->RegisterIsAllocatedInThisScope(reg)));
    result_register_ = reg;
    set_result_identified();
  }

  Register ResultRegister() const { return result_register_; }

 private:
  Register result_register_;
};


BytecodeGenerator::AssignmentHazardHelper::AssignmentHazardHelper(
    BytecodeGenerator* generator)
    : generator_(generator),
      alias_mappings_(generator->zone()),
      aliased_locals_and_parameters_(generator->zone()),
      execution_result_(nullptr),
      scope_depth_(0) {}


void BytecodeGenerator::AssignmentHazardHelper::EnterScope() {
  DCHECK_GE(scope_depth_, 0);
  if (scope_depth_++ == 0) {
    execution_result_ = generator_->execution_result();
  }
}


void BytecodeGenerator::AssignmentHazardHelper::LeaveScope() {
  DCHECK_GT(scope_depth_, 0);
  if (--scope_depth_ == 0) {
    DCHECK_EQ(execution_result_, generator_->execution_result());
    RestoreAliasedLocalsAndParameters();
  }
}


// Returns a register that a load instruction should use when
// loading from |reg|. This allows an alias for a modified version
// of |reg| to be used within a hazard regions.
MUST_USE_RESULT Register
BytecodeGenerator::AssignmentHazardHelper::GetRegisterForLoad(Register reg) {
  if (scope_depth_ == 0) {
    return reg;
  } else {
    // A load from |reg| is to be issued. The register is placed in
    // the mappings table initially mapping to itself. Future stores
    // will update the mapping with temporaries thus preserving the
    // original register's value.
    //
    // NB This insert only updates the table if no mapping exists
    // already (std::map::insert semantics).
    auto insert_result =
        alias_mappings_.insert(std::make_pair(reg.index(), reg.index()));
    auto mapping = insert_result.first;
    // Return the current alias for reg.
    return Register(mapping->second);
  }
}


// Returns a register that a store instruction should use when
// loading from |reg|. This allows an alias for a modified version
// of |reg| to be used within hazard regions.
MUST_USE_RESULT Register
BytecodeGenerator::AssignmentHazardHelper::GetRegisterForStore(Register reg) {
  if (scope_depth_ == 0 ||
      alias_mappings_.find(reg.index()) == alias_mappings_.end()) {
    // If not in a hazard region or a load for this register has not
    // occurred no mapping is necessary.
    return reg;
  } else {
    // Storing to a register with 1 or more loads issued. The
    // register is mapped to a temporary alias so we don't overwrite
    // the lhs value, e.g.  y = x + (x = 1); has a register for x on
    // the lhs and needs a new register x' for the upcoming store on
    // the rhs as the original x is an input to the add operation.
    Register alias = execution_result_->NewRegister();
    alias_mappings_[reg.index()] = alias.index();
    if (generator_->builder()->RegisterIsParameterOrLocal(reg)) {
      // Keep track of registers that need to be restored on exit
      // from the assignment hazard region.
      aliased_locals_and_parameters_.insert(reg.index());
    }
    return alias;
  }
}


void BytecodeGenerator::AssignmentHazardHelper::
    RestoreAliasedLocalsAndParameters() {
  DCHECK(scope_depth_ == 0);
  // Move temporary registers holding values for locals and
  // parameters back into their local and parameter registers.
  for (auto reg = aliased_locals_and_parameters_.begin();
       reg != aliased_locals_and_parameters_.end(); reg++) {
    auto mapping = alias_mappings_.find(*reg);
    if (mapping != alias_mappings_.end()) {
      generator_->builder()->MoveRegister(Register(mapping->second),
                                          Register(*reg));
    }
  }
  alias_mappings_.clear();
  aliased_locals_and_parameters_.clear();
}


class BytecodeGenerator::AssignmentHazardScope final {
 public:
  explicit AssignmentHazardScope(BytecodeGenerator* generator)
      : generator_(generator) {
    generator_->assignment_hazard_helper()->EnterScope();
  }

  ~AssignmentHazardScope() {
    generator_->assignment_hazard_helper()->LeaveScope();
  }

 private:
  BytecodeGenerator* generator_;

  DISALLOW_COPY_AND_ASSIGN(AssignmentHazardScope);
};


BytecodeGenerator::BytecodeGenerator(Isolate* isolate, Zone* zone)
    : isolate_(isolate),
      zone_(zone),
      builder_(isolate, zone),
      info_(nullptr),
      scope_(nullptr),
      globals_(0, zone),
      execution_control_(nullptr),
      execution_context_(nullptr),
      execution_result_(nullptr),
      assignment_hazard_helper_(this) {
  InitializeAstVisitor(isolate);
}


Handle<BytecodeArray> BytecodeGenerator::MakeBytecode(CompilationInfo* info) {
  set_info(info);
  set_scope(info->scope());

  // Initialize the incoming context.
  ContextScope incoming_context(this, scope(), false);

  builder()->set_parameter_count(info->num_parameters_including_this());
  builder()->set_locals_count(scope()->num_stack_slots());
  builder()->set_context_count(scope()->MaxNestedContextChainLength());

  // Build function context only if there are context allocated variables.
  if (scope()->NeedsContext()) {
    // Push a new inner context scope for the function.
    VisitNewLocalFunctionContext();
    ContextScope local_function_context(this, scope(), false);
    VisitBuildLocalActivationContext();
    MakeBytecodeBody();
  } else {
    MakeBytecodeBody();
  }

  set_scope(nullptr);
  set_info(nullptr);
  return builder_.ToBytecodeArray();
}


void BytecodeGenerator::MakeBytecodeBody() {
  // Build the arguments object if it is used.
  VisitArgumentsObject(scope()->arguments());

  // TODO(mythria): Build rest arguments array if it is used.
  int rest_index;
  if (scope()->rest_parameter(&rest_index)) {
    UNIMPLEMENTED();
  }

  // Build assignment to {.this_function} variable if it is used.
  VisitThisFunctionVariable(scope()->this_function_var());

  // Build assignment to {new.target} variable if it is used.
  VisitNewTargetVariable(scope()->new_target_var());

  // TODO(rmcilroy): Emit tracing call if requested to do so.
  if (FLAG_trace) {
    UNIMPLEMENTED();
  }

  // Visit illegal re-declaration and bail out if it exists.
  if (scope()->HasIllegalRedeclaration()) {
    Visit(scope()->GetIllegalRedeclaration());
    return;
  }

  // Visit declarations within the function scope.
  VisitDeclarations(scope()->declarations());

  // Visit statements in the function body.
  VisitStatements(info()->literal()->body());
}


void BytecodeGenerator::VisitBlock(Block* stmt) {
  BlockBuilder block_builder(this->builder());
  ControlScopeForBreakable execution_control(this, stmt, &block_builder);

  if (stmt->scope() == NULL) {
    // Visit statements in the same scope, no declarations.
    VisitStatements(stmt->statements());
  } else {
    // Visit declarations and statements in a block scope.
    if (stmt->scope()->NeedsContext()) {
      VisitNewLocalBlockContext(stmt->scope());
      ContextScope scope(this, stmt->scope());
      VisitDeclarations(stmt->scope()->declarations());
      VisitStatements(stmt->statements());
    } else {
      VisitDeclarations(stmt->scope()->declarations());
      VisitStatements(stmt->statements());
    }
  }
  if (stmt->labels() != nullptr) block_builder.EndBlock();
}


void BytecodeGenerator::VisitVariableDeclaration(VariableDeclaration* decl) {
  Variable* variable = decl->proxy()->var();
  VariableMode mode = decl->mode();
  // Const and let variables are initialized with the hole so that we can
  // check that they are only assigned once.
  bool hole_init = mode == CONST || mode == CONST_LEGACY || mode == LET;
  switch (variable->location()) {
    case VariableLocation::GLOBAL:
    case VariableLocation::UNALLOCATED: {
      Handle<Oddball> value = variable->binding_needs_init()
                                  ? isolate()->factory()->the_hole_value()
                                  : isolate()->factory()->undefined_value();
      globals()->push_back(variable->name());
      globals()->push_back(value);
      break;
    }
    case VariableLocation::LOCAL:
      if (hole_init) {
        Register destination(variable->index());
        builder()->LoadTheHole().StoreAccumulatorInRegister(destination);
      }
      break;
    case VariableLocation::PARAMETER:
      if (hole_init) {
        // The parameter indices are shifted by 1 (receiver is variable
        // index -1 but is parameter index 0 in BytecodeArrayBuilder).
        Register destination(builder()->Parameter(variable->index() + 1));
        builder()->LoadTheHole().StoreAccumulatorInRegister(destination);
      }
      break;
    case VariableLocation::CONTEXT:
      if (hole_init) {
        builder()->LoadTheHole().StoreContextSlot(execution_context()->reg(),
                                                  variable->index());
      }
      break;
    case VariableLocation::LOOKUP:
      UNIMPLEMENTED();
      break;
  }
}


void BytecodeGenerator::VisitFunctionDeclaration(FunctionDeclaration* decl) {
  Variable* variable = decl->proxy()->var();
  switch (variable->location()) {
    case VariableLocation::GLOBAL:
    case VariableLocation::UNALLOCATED: {
      Handle<SharedFunctionInfo> function = Compiler::GetSharedFunctionInfo(
          decl->fun(), info()->script(), info());
      // Check for stack-overflow exception.
      if (function.is_null()) return SetStackOverflow();
      globals()->push_back(variable->name());
      globals()->push_back(function);
      break;
    }
    case VariableLocation::PARAMETER:
    case VariableLocation::LOCAL: {
      VisitForAccumulatorValue(decl->fun());
      VisitVariableAssignment(variable, FeedbackVectorSlot::Invalid());
      break;
    }
    case VariableLocation::CONTEXT: {
      DCHECK_EQ(0, execution_context()->ContextChainDepth(variable->scope()));
      VisitForAccumulatorValue(decl->fun());
      builder()->StoreContextSlot(execution_context()->reg(),
                                  variable->index());
      break;
    }
    case VariableLocation::LOOKUP:
      UNIMPLEMENTED();
  }
}


void BytecodeGenerator::VisitImportDeclaration(ImportDeclaration* decl) {
  UNIMPLEMENTED();
}


void BytecodeGenerator::VisitExportDeclaration(ExportDeclaration* decl) {
  UNIMPLEMENTED();
}


void BytecodeGenerator::VisitDeclarations(
    ZoneList<Declaration*>* declarations) {
  DCHECK(globals()->empty());
  AstVisitor::VisitDeclarations(declarations);
  if (globals()->empty()) return;
  int array_index = 0;
  Handle<FixedArray> data = isolate()->factory()->NewFixedArray(
      static_cast<int>(globals()->size()), TENURED);
  for (Handle<Object> obj : *globals()) data->set(array_index++, *obj);
  int encoded_flags = DeclareGlobalsEvalFlag::encode(info()->is_eval()) |
                      DeclareGlobalsNativeFlag::encode(info()->is_native()) |
                      DeclareGlobalsLanguageMode::encode(language_mode());

  TemporaryRegisterScope temporary_register_scope(builder());
  Register pairs = temporary_register_scope.NewRegister();
  builder()->LoadLiteral(data);
  builder()->StoreAccumulatorInRegister(pairs);

  Register flags = temporary_register_scope.NewRegister();
  builder()->LoadLiteral(Smi::FromInt(encoded_flags));
  builder()->StoreAccumulatorInRegister(flags);
  DCHECK(flags.index() == pairs.index() + 1);

  builder()->CallRuntime(Runtime::kDeclareGlobals, pairs, 2);
  globals()->clear();
}


void BytecodeGenerator::VisitExpressionStatement(ExpressionStatement* stmt) {
  EffectResultScope statement_result_scope(this);
  VisitForEffect(stmt->expression());
}


void BytecodeGenerator::VisitEmptyStatement(EmptyStatement* stmt) {
}


void BytecodeGenerator::VisitIfStatement(IfStatement* stmt) {
  BytecodeLabel else_label, end_label;
  if (stmt->condition()->ToBooleanIsTrue()) {
    // Generate then block unconditionally as always true.
    Visit(stmt->then_statement());
  } else if (stmt->condition()->ToBooleanIsFalse()) {
    // Generate else block unconditionally if it exists.
    if (stmt->HasElseStatement()) {
      Visit(stmt->else_statement());
    }
  } else {
    // TODO(oth): If then statement is BreakStatement or
    // ContinueStatement we can reduce number of generated
    // jump/jump_ifs here. See BasicLoops test.
    VisitForAccumulatorValue(stmt->condition());
    builder()->JumpIfFalse(&else_label);
    Visit(stmt->then_statement());
    if (stmt->HasElseStatement()) {
      builder()->Jump(&end_label);
      builder()->Bind(&else_label);
      Visit(stmt->else_statement());
    } else {
      builder()->Bind(&else_label);
    }
    builder()->Bind(&end_label);
  }
}


void BytecodeGenerator::VisitSloppyBlockFunctionStatement(
    SloppyBlockFunctionStatement* stmt) {
  Visit(stmt->statement());
}


void BytecodeGenerator::VisitContinueStatement(ContinueStatement* stmt) {
  execution_control()->Continue(stmt->target());
}


void BytecodeGenerator::VisitBreakStatement(BreakStatement* stmt) {
  execution_control()->Break(stmt->target());
}


void BytecodeGenerator::VisitReturnStatement(ReturnStatement* stmt) {
  EffectResultScope statement_result_scope(this);
  VisitForAccumulatorValue(stmt->expression());
  builder()->Return();
}


void BytecodeGenerator::VisitWithStatement(WithStatement* stmt) {
  UNIMPLEMENTED();
}


void BytecodeGenerator::VisitSwitchStatement(SwitchStatement* stmt) {
  ZoneList<CaseClause*>* clauses = stmt->cases();
  SwitchBuilder switch_builder(builder(), clauses->length());
  ControlScopeForBreakable scope(this, stmt, &switch_builder);
  int default_index = -1;

  // Keep the switch value in a register until a case matches.
  Register tag = VisitForRegisterValue(stmt->tag());

  // Iterate over all cases and create nodes for label comparison.
  BytecodeLabel done_label;
  for (int i = 0; i < clauses->length(); i++) {
    CaseClause* clause = clauses->at(i);

    // The default is not a test, remember index.
    if (clause->is_default()) {
      default_index = i;
      continue;
    }

    // Perform label comparison as if via '===' with tag.
    VisitForAccumulatorValue(clause->label());
    builder()->CompareOperation(Token::Value::EQ_STRICT, tag,
                                language_mode_strength());
    switch_builder.Case(i);
  }

  if (default_index >= 0) {
    // Emit default jump if there is a default case.
    switch_builder.DefaultAt(default_index);
  } else {
    // Otherwise if we have reached here none of the cases matched, so jump to
    // done.
    builder()->Jump(&done_label);
  }

  // Iterate over all cases and create the case bodies.
  for (int i = 0; i < clauses->length(); i++) {
    CaseClause* clause = clauses->at(i);
    switch_builder.SetCaseTarget(i);
    VisitStatements(clause->statements());
  }
  builder()->Bind(&done_label);

  switch_builder.SetBreakTarget(done_label);
}


void BytecodeGenerator::VisitCaseClause(CaseClause* clause) {
  // Handled entirely in VisitSwitchStatement.
  UNREACHABLE();
}


void BytecodeGenerator::VisitDoWhileStatement(DoWhileStatement* stmt) {
  LoopBuilder loop_builder(builder());
  ControlScopeForIteration execution_control(this, stmt, &loop_builder);
  loop_builder.LoopHeader();
  if (stmt->cond()->ToBooleanIsFalse()) {
    Visit(stmt->body());
    loop_builder.Condition();
  } else if (stmt->cond()->ToBooleanIsTrue()) {
    loop_builder.Condition();
    Visit(stmt->body());
    loop_builder.JumpToHeader();
  } else {
    Visit(stmt->body());
    loop_builder.Condition();
    VisitForAccumulatorValue(stmt->cond());
    loop_builder.JumpToHeaderIfTrue();
  }
  loop_builder.EndLoop();
}


void BytecodeGenerator::VisitWhileStatement(WhileStatement* stmt) {
  if (stmt->cond()->ToBooleanIsFalse()) {
    // If the condition is false there is no need to generate the loop.
    return;
  }

  LoopBuilder loop_builder(builder());
  ControlScopeForIteration execution_control(this, stmt, &loop_builder);
  loop_builder.LoopHeader();
  loop_builder.Condition();
  if (!stmt->cond()->ToBooleanIsTrue()) {
    VisitForAccumulatorValue(stmt->cond());
    loop_builder.BreakIfFalse();
  }
  Visit(stmt->body());
  loop_builder.JumpToHeader();
  loop_builder.EndLoop();
}


void BytecodeGenerator::VisitForStatement(ForStatement* stmt) {
  if (stmt->init() != nullptr) {
    Visit(stmt->init());
  }
  if (stmt->cond() && stmt->cond()->ToBooleanIsFalse()) {
    // If the condition is known to be false there is no need to generate
    // body, next or condition blocks. Init block should be generated.
    return;
  }

  LoopBuilder loop_builder(builder());
  ControlScopeForIteration execution_control(this, stmt, &loop_builder);

  loop_builder.LoopHeader();
  loop_builder.Condition();
  if (stmt->cond() && !stmt->cond()->ToBooleanIsTrue()) {
    VisitForAccumulatorValue(stmt->cond());
    loop_builder.BreakIfFalse();
  }
  Visit(stmt->body());
  if (stmt->next() != nullptr) {
    loop_builder.Next();
    Visit(stmt->next());
  }
  loop_builder.JumpToHeader();
  loop_builder.EndLoop();
}


void BytecodeGenerator::VisitForInAssignment(Expression* expr,
                                             FeedbackVectorSlot slot) {
  DCHECK(expr->IsValidReferenceExpression());

  // Evaluate assignment starting with the value to be stored in the
  // accumulator.
  Property* property = expr->AsProperty();
  LhsKind assign_type = Property::GetAssignType(property);
  switch (assign_type) {
    case VARIABLE: {
      Variable* variable = expr->AsVariableProxy()->var();
      VisitVariableAssignment(variable, slot);
      break;
    }
    case NAMED_PROPERTY: {
      TemporaryRegisterScope temporary_register_scope(builder());
      Register value = temporary_register_scope.NewRegister();
      builder()->StoreAccumulatorInRegister(value);
      Register object = VisitForRegisterValue(property->obj());
      Handle<String> name = property->key()->AsLiteral()->AsPropertyName();
      builder()->LoadAccumulatorWithRegister(value);
      builder()->StoreNamedProperty(object, name, feedback_index(slot),
                                    language_mode());
      break;
    }
    case KEYED_PROPERTY: {
      TemporaryRegisterScope temporary_register_scope(builder());
      Register value = temporary_register_scope.NewRegister();
      builder()->StoreAccumulatorInRegister(value);
      Register object = VisitForRegisterValue(property->obj());
      Register key = VisitForRegisterValue(property->key());
      builder()->LoadAccumulatorWithRegister(value);
      builder()->StoreKeyedProperty(object, key, feedback_index(slot),
                                    language_mode());
      break;
    }
    case NAMED_SUPER_PROPERTY:
    case KEYED_SUPER_PROPERTY:
      UNIMPLEMENTED();
  }
}


void BytecodeGenerator::VisitForInStatement(ForInStatement* stmt) {
  EffectResultScope statement_result_scope(this);
  if (stmt->subject()->IsNullLiteral() ||
      stmt->subject()->IsUndefinedLiteral(isolate())) {
    // ForIn generates lots of code, skip if it wouldn't produce any effects.
    return;
  }

  LoopBuilder loop_builder(builder());
  ControlScopeForIteration control_scope(this, stmt, &loop_builder);
  BytecodeLabel subject_null_label, subject_undefined_label, not_object_label;

  // Prepare the state for executing ForIn.
  VisitForAccumulatorValue(stmt->subject());
  builder()->JumpIfUndefined(&subject_undefined_label);
  builder()->JumpIfNull(&subject_null_label);
  Register receiver = execution_result()->NewRegister();
  builder()->CastAccumulatorToJSObject();
  builder()->JumpIfNull(&not_object_label);
  builder()->StoreAccumulatorInRegister(receiver);
  Register cache_type = execution_result()->NewRegister();
  Register cache_array = execution_result()->NewRegister();
  Register cache_length = execution_result()->NewRegister();
  builder()->ForInPrepare(cache_type, cache_array, cache_length);

  // Set up loop counter
  Register index = execution_result()->NewRegister();
  builder()->LoadLiteral(Smi::FromInt(0));
  builder()->StoreAccumulatorInRegister(index);

  // The loop
  loop_builder.LoopHeader();
  loop_builder.Condition();
  builder()->ForInDone(index, cache_length);
  loop_builder.BreakIfTrue();
  builder()->ForInNext(receiver, cache_type, cache_array, index);
  loop_builder.ContinueIfUndefined();
  VisitForInAssignment(stmt->each(), stmt->EachFeedbackSlot());
  Visit(stmt->body());
  loop_builder.Next();
  builder()->ForInStep(index);
  builder()->StoreAccumulatorInRegister(index);
  loop_builder.JumpToHeader();
  loop_builder.EndLoop();
  builder()->Bind(&not_object_label);
  builder()->Bind(&subject_null_label);
  builder()->Bind(&subject_undefined_label);
}


void BytecodeGenerator::VisitForOfStatement(ForOfStatement* stmt) {
  UNIMPLEMENTED();
}


void BytecodeGenerator::VisitTryCatchStatement(TryCatchStatement* stmt) {
  if (FLAG_ignition_fake_try_catch) {
    Visit(stmt->try_block());
    return;
  }
  UNIMPLEMENTED();
}


void BytecodeGenerator::VisitTryFinallyStatement(TryFinallyStatement* stmt) {
  if (FLAG_ignition_fake_try_catch) {
    Visit(stmt->try_block());
    Visit(stmt->finally_block());
    return;
  }
  UNIMPLEMENTED();
}


void BytecodeGenerator::VisitDebuggerStatement(DebuggerStatement* stmt) {
  UNIMPLEMENTED();
}


void BytecodeGenerator::VisitFunctionLiteral(FunctionLiteral* expr) {
  // Find or build a shared function info.
  Handle<SharedFunctionInfo> shared_info =
      Compiler::GetSharedFunctionInfo(expr, info()->script(), info());
  CHECK(!shared_info.is_null());  // TODO(rmcilroy): Set stack overflow?
  builder()->CreateClosure(shared_info,
                           expr->pretenure() ? TENURED : NOT_TENURED);
  execution_result()->SetResultInAccumulator();
}


void BytecodeGenerator::VisitClassLiteral(ClassLiteral* expr) {
  UNIMPLEMENTED();
}


void BytecodeGenerator::VisitNativeFunctionLiteral(
    NativeFunctionLiteral* expr) {
  UNIMPLEMENTED();
}


void BytecodeGenerator::VisitDoExpression(DoExpression* expr) {
  UNIMPLEMENTED();
}


void BytecodeGenerator::VisitConditional(Conditional* expr) {
  // TODO(rmcilroy): Spot easy cases where there code would not need to
  // emit the then block or the else block, e.g. condition is
  // obviously true/1/false/0.

  BytecodeLabel else_label, end_label;

  VisitForAccumulatorValue(expr->condition());
  builder()->JumpIfFalse(&else_label);

  VisitForAccumulatorValue(expr->then_expression());
  builder()->Jump(&end_label);

  builder()->Bind(&else_label);
  VisitForAccumulatorValue(expr->else_expression());
  builder()->Bind(&end_label);

  execution_result()->SetResultInAccumulator();
}


void BytecodeGenerator::VisitLiteral(Literal* expr) {
  if (!execution_result()->IsEffect()) {
    Handle<Object> value = expr->value();
    if (value->IsSmi()) {
      builder()->LoadLiteral(Smi::cast(*value));
    } else if (value->IsUndefined()) {
      builder()->LoadUndefined();
    } else if (value->IsTrue()) {
      builder()->LoadTrue();
    } else if (value->IsFalse()) {
      builder()->LoadFalse();
    } else if (value->IsNull()) {
      builder()->LoadNull();
    } else if (value->IsTheHole()) {
      builder()->LoadTheHole();
    } else {
      builder()->LoadLiteral(value);
    }
    execution_result()->SetResultInAccumulator();
  }
}


void BytecodeGenerator::VisitRegExpLiteral(RegExpLiteral* expr) {
  // Materialize a regular expression literal.
  TemporaryRegisterScope temporary_register_scope(builder());
  builder()->CreateRegExpLiteral(expr->pattern(), expr->literal_index(),
                                 expr->flags());
  execution_result()->SetResultInAccumulator();
}


void BytecodeGenerator::VisitObjectLiteral(ObjectLiteral* expr) {
  // Deep-copy the literal boilerplate.
  builder()->CreateObjectLiteral(expr->constant_properties(),
                                 expr->literal_index(),
                                 expr->ComputeFlags(true));

  TemporaryRegisterScope temporary_register_scope(builder());
  Register literal;

  // Store computed values into the literal.
  bool literal_in_accumulator = true;
  int property_index = 0;
  AccessorTable accessor_table(zone());
  for (; property_index < expr->properties()->length(); property_index++) {
    TemporaryRegisterScope inner_temporary_register_scope(builder());
    ObjectLiteral::Property* property = expr->properties()->at(property_index);
    if (property->is_computed_name()) break;
    if (property->IsCompileTimeValue()) continue;

    if (literal_in_accumulator) {
      literal = temporary_register_scope.NewRegister();
      builder()->StoreAccumulatorInRegister(literal);
      literal_in_accumulator = false;
    }

    Literal* literal_key = property->key()->AsLiteral();
    switch (property->kind()) {
      case ObjectLiteral::Property::CONSTANT:
        UNREACHABLE();
      case ObjectLiteral::Property::MATERIALIZED_LITERAL:
        DCHECK(!CompileTimeValue::IsCompileTimeValue(property->value()));
      // Fall through.
      case ObjectLiteral::Property::COMPUTED: {
        // It is safe to use [[Put]] here because the boilerplate already
        // contains computed properties with an uninitialized value.
        if (literal_key->value()->IsInternalizedString()) {
          if (property->emit_store()) {
            VisitForAccumulatorValue(property->value());
            builder()->StoreNamedProperty(
                literal, literal_key->AsPropertyName(),
                feedback_index(property->GetSlot(0)), language_mode());
          } else {
            VisitForEffect(property->value());
          }
        } else {
          inner_temporary_register_scope.PrepareForConsecutiveAllocations(3);
          Register key =
              inner_temporary_register_scope.NextConsecutiveRegister();
          Register value =
              inner_temporary_register_scope.NextConsecutiveRegister();
          Register language =
              inner_temporary_register_scope.NextConsecutiveRegister();
          // TODO(oth): This is problematic - can't assume contiguous here.
          // literal is allocated in temporary_register_scope, whereas
          // key, value, language are in another.
          DCHECK(Register::AreContiguous(literal, key, value, language));
          VisitForAccumulatorValue(property->key());
          builder()->StoreAccumulatorInRegister(key);
          VisitForAccumulatorValue(property->value());
          builder()->StoreAccumulatorInRegister(value);
          if (property->emit_store()) {
            builder()
                ->LoadLiteral(Smi::FromInt(SLOPPY))
                .StoreAccumulatorInRegister(language)
                .CallRuntime(Runtime::kSetProperty, literal, 4);
            VisitSetHomeObject(value, literal, property);
          }
        }
        break;
      }
      case ObjectLiteral::Property::PROTOTYPE: {
        inner_temporary_register_scope.PrepareForConsecutiveAllocations(1);
        DCHECK(property->emit_store());
        Register value =
            inner_temporary_register_scope.NextConsecutiveRegister();
        DCHECK(Register::AreContiguous(literal, value));
        VisitForAccumulatorValue(property->value());
        builder()->StoreAccumulatorInRegister(value).CallRuntime(
            Runtime::kInternalSetPrototype, literal, 2);
        break;
      }
      case ObjectLiteral::Property::GETTER:
        if (property->emit_store()) {
          accessor_table.lookup(literal_key)->second->getter = property;
        }
        break;
      case ObjectLiteral::Property::SETTER:
        if (property->emit_store()) {
          accessor_table.lookup(literal_key)->second->setter = property;
        }
        break;
    }
  }

  // Define accessors, using only a single call to the runtime for each pair of
  // corresponding getters and setters.
  for (AccessorTable::Iterator it = accessor_table.begin();
       it != accessor_table.end(); ++it) {
    TemporaryRegisterScope inner_temporary_register_scope(builder());
    inner_temporary_register_scope.PrepareForConsecutiveAllocations(4);
    Register name = inner_temporary_register_scope.NextConsecutiveRegister();
    Register getter = inner_temporary_register_scope.NextConsecutiveRegister();
    Register setter = inner_temporary_register_scope.NextConsecutiveRegister();
    Register attr = inner_temporary_register_scope.NextConsecutiveRegister();
    DCHECK(Register::AreContiguous(literal, name, getter, setter, attr));
    VisitForAccumulatorValue(it->first);
    builder()->StoreAccumulatorInRegister(name);
    VisitObjectLiteralAccessor(literal, it->second->getter, getter);
    VisitObjectLiteralAccessor(literal, it->second->setter, setter);
    builder()
        ->LoadLiteral(Smi::FromInt(NONE))
        .StoreAccumulatorInRegister(attr)
        .CallRuntime(Runtime::kDefineAccessorPropertyUnchecked, literal, 5);
  }

  // Object literals have two parts. The "static" part on the left contains no
  // computed property names, and so we can compute its map ahead of time; see
  // Runtime_CreateObjectLiteralBoilerplate. The second "dynamic" part starts
  // with the first computed property name and continues with all properties to
  // its right. All the code from above initializes the static component of the
  // object literal, and arranges for the map of the result to reflect the
  // static order in which the keys appear. For the dynamic properties, we
  // compile them into a series of "SetOwnProperty" runtime calls. This will
  // preserve insertion order.
  for (; property_index < expr->properties()->length(); property_index++) {
    ObjectLiteral::Property* property = expr->properties()->at(property_index);

    if (literal_in_accumulator) {
      temporary_register_scope.PrepareForConsecutiveAllocations(4);
      literal = temporary_register_scope.NextConsecutiveRegister();
      builder()->StoreAccumulatorInRegister(literal);
      literal_in_accumulator = false;
    }

    if (property->kind() == ObjectLiteral::Property::PROTOTYPE) {
      DCHECK(property->emit_store());
      TemporaryRegisterScope inner_temporary_register_scope(builder());
      Register value = inner_temporary_register_scope.NewRegister();
      DCHECK(Register::AreContiguous(literal, value));
      VisitForAccumulatorValue(property->value());
      builder()->StoreAccumulatorInRegister(value).CallRuntime(
          Runtime::kInternalSetPrototype, literal, 2);
      continue;
    }

    TemporaryRegisterScope inner_temporary_register_scope(builder());
    inner_temporary_register_scope.PrepareForConsecutiveAllocations(3);
    Register key = inner_temporary_register_scope.NextConsecutiveRegister();
    Register value = inner_temporary_register_scope.NextConsecutiveRegister();
    Register attr = inner_temporary_register_scope.NextConsecutiveRegister();
    DCHECK(Register::AreContiguous(literal, key, value, attr));

    VisitForAccumulatorValue(property->key());
    builder()->CastAccumulatorToName().StoreAccumulatorInRegister(key);
    VisitForAccumulatorValue(property->value());
    builder()->StoreAccumulatorInRegister(value);
    VisitSetHomeObject(value, literal, property);
    builder()->LoadLiteral(Smi::FromInt(NONE)).StoreAccumulatorInRegister(attr);
    Runtime::FunctionId function_id = static_cast<Runtime::FunctionId>(-1);
    switch (property->kind()) {
      case ObjectLiteral::Property::CONSTANT:
      case ObjectLiteral::Property::COMPUTED:
      case ObjectLiteral::Property::MATERIALIZED_LITERAL:
        function_id = Runtime::kDefineDataPropertyUnchecked;
        break;
      case ObjectLiteral::Property::PROTOTYPE:
        UNREACHABLE();  // Handled specially above.
        break;
      case ObjectLiteral::Property::GETTER:
        function_id = Runtime::kDefineGetterPropertyUnchecked;
        break;
      case ObjectLiteral::Property::SETTER:
        function_id = Runtime::kDefineSetterPropertyUnchecked;
        break;
    }
    builder()->CallRuntime(function_id, literal, 4);
  }

  // Transform literals that contain functions to fast properties.
  if (expr->has_function()) {
    DCHECK(!literal_in_accumulator);
    builder()->CallRuntime(Runtime::kToFastProperties, literal, 1);
  }

  if (!literal_in_accumulator) {
    // Restore literal array into accumulator.
    builder()->LoadAccumulatorWithRegister(literal);
  }
  execution_result()->SetResultInAccumulator();
}


void BytecodeGenerator::VisitArrayLiteral(ArrayLiteral* expr) {
  // Deep-copy the literal boilerplate.
  builder()->CreateArrayLiteral(expr->constant_elements(),
                                expr->literal_index(),
                                expr->ComputeFlags(true));

  TemporaryRegisterScope temporary_register_scope(builder());
  Register index, literal;

  // Evaluate all the non-constant subexpressions and store them into the
  // newly cloned array.
  bool literal_in_accumulator = true;
  for (int array_index = 0; array_index < expr->values()->length();
       array_index++) {
    Expression* subexpr = expr->values()->at(array_index);
    if (CompileTimeValue::IsCompileTimeValue(subexpr)) continue;
    if (subexpr->IsSpread()) {
      // TODO(rmcilroy): Deal with spread expressions.
      UNIMPLEMENTED();
    }

    if (literal_in_accumulator) {
      index = temporary_register_scope.NewRegister();
      literal = temporary_register_scope.NewRegister();
      builder()->StoreAccumulatorInRegister(literal);
      literal_in_accumulator = false;
    }

    FeedbackVectorSlot slot = expr->LiteralFeedbackSlot();
    builder()
        ->LoadLiteral(Smi::FromInt(array_index))
        .StoreAccumulatorInRegister(index);
    VisitForAccumulatorValue(subexpr);
    builder()->StoreKeyedProperty(literal, index, feedback_index(slot),
                                  language_mode());
  }

  if (!literal_in_accumulator) {
    // Restore literal array into accumulator.
    builder()->LoadAccumulatorWithRegister(literal);
  }
  execution_result()->SetResultInAccumulator();
}


void BytecodeGenerator::VisitVariableProxy(VariableProxy* proxy) {
  VisitVariableLoad(proxy->var(), proxy->VariableFeedbackSlot());
}


void BytecodeGenerator::VisitVariableLoad(Variable* variable,
                                          FeedbackVectorSlot slot,
                                          TypeofMode typeof_mode) {
  switch (variable->location()) {
    case VariableLocation::LOCAL: {
      Register source(Register(variable->index()));
      source = assignment_hazard_helper()->GetRegisterForLoad(source);
      execution_result()->SetResultInRegister(source);
      break;
    }
    case VariableLocation::PARAMETER: {
      // The parameter indices are shifted by 1 (receiver is variable
      // index -1 but is parameter index 0 in BytecodeArrayBuilder).
      Register source = builder()->Parameter(variable->index() + 1);
      source = assignment_hazard_helper()->GetRegisterForLoad(source);
      execution_result()->SetResultInRegister(source);
      break;
    }
    case VariableLocation::GLOBAL:
    case VariableLocation::UNALLOCATED: {
      builder()->LoadGlobal(variable->name(), feedback_index(slot),
                            language_mode(), typeof_mode);
      execution_result()->SetResultInAccumulator();
      break;
    }
    case VariableLocation::CONTEXT: {
      int depth = execution_context()->ContextChainDepth(variable->scope());
      ContextScope* context = execution_context()->Previous(depth);
      Register context_reg;
      if (context) {
        context_reg = context->reg();
      } else {
        context_reg = execution_result()->NewRegister();
        // Walk the context chain to find the context at the given depth.
        // TODO(rmcilroy): Perform this work in a bytecode handler once we have
        // a generic mechanism for performing jumps in interpreter.cc.
        // TODO(mythria): Also update bytecode graph builder with correct depth
        // when this changes.
        builder()
            ->LoadAccumulatorWithRegister(execution_context()->reg())
            .StoreAccumulatorInRegister(context_reg);
        for (int i = 0; i < depth; ++i) {
          builder()
              ->LoadContextSlot(context_reg, Context::PREVIOUS_INDEX)
              .StoreAccumulatorInRegister(context_reg);
        }
      }
      builder()->LoadContextSlot(context_reg, variable->index());
      execution_result()->SetResultInAccumulator();
      // TODO(rmcilroy): Perform check for uninitialized legacy const, const and
      // let variables.
      break;
    }
    case VariableLocation::LOOKUP: {
      builder()->LoadLookupSlot(variable->name(), typeof_mode);
      execution_result()->SetResultInAccumulator();
      break;
    }
  }
}


void BytecodeGenerator::VisitVariableLoadForAccumulatorValue(
    Variable* variable, FeedbackVectorSlot slot, TypeofMode typeof_mode) {
  AccumulatorResultScope accumulator_result(this);
  VisitVariableLoad(variable, slot, typeof_mode);
}


Register BytecodeGenerator::VisitVariableLoadForRegisterValue(
    Variable* variable, FeedbackVectorSlot slot, TypeofMode typeof_mode) {
  RegisterResultScope register_scope(this);
  VisitVariableLoad(variable, slot, typeof_mode);
  return register_scope.ResultRegister();
}


void BytecodeGenerator::VisitVariableAssignment(Variable* variable,
                                                FeedbackVectorSlot slot) {
  switch (variable->location()) {
    case VariableLocation::LOCAL: {
      // TODO(rmcilroy): support const mode initialization.
      Register destination(variable->index());
      destination =
          assignment_hazard_helper()->GetRegisterForStore(destination);
      builder()->StoreAccumulatorInRegister(destination);
      break;
    }
    case VariableLocation::PARAMETER: {
      // The parameter indices are shifted by 1 (receiver is variable
      // index -1 but is parameter index 0 in BytecodeArrayBuilder).
      Register destination(builder()->Parameter(variable->index() + 1));
      destination =
          assignment_hazard_helper()->GetRegisterForStore(destination);

      builder()->StoreAccumulatorInRegister(destination);
      break;
    }
    case VariableLocation::GLOBAL:
    case VariableLocation::UNALLOCATED: {
      builder()->StoreGlobal(variable->name(), feedback_index(slot),
                             language_mode());
      break;
    }
    case VariableLocation::CONTEXT: {
      // TODO(rmcilroy): support const mode initialization.
      int depth = execution_context()->ContextChainDepth(variable->scope());
      ContextScope* context = execution_context()->Previous(depth);
      Register context_reg;
      if (context) {
        context_reg = context->reg();
      } else {
        Register value_temp = execution_result()->NewRegister();
        context_reg = execution_result()->NewRegister();
        // Walk the context chain to find the context at the given depth.
        // TODO(rmcilroy): Perform this work in a bytecode handler once we have
        // a generic mechanism for performing jumps in interpreter.cc.
        // TODO(mythria): Also update bytecode graph builder with correct depth
        // when this changes.
        builder()
            ->StoreAccumulatorInRegister(value_temp)
            .LoadAccumulatorWithRegister(execution_context()->reg())
            .StoreAccumulatorInRegister(context_reg);
        for (int i = 0; i < depth; ++i) {
          builder()
              ->LoadContextSlot(context_reg, Context::PREVIOUS_INDEX)
              .StoreAccumulatorInRegister(context_reg);
        }
        builder()->LoadAccumulatorWithRegister(value_temp);
      }
      builder()->StoreContextSlot(context_reg, variable->index());
      break;
    }
    case VariableLocation::LOOKUP: {
      builder()->StoreLookupSlot(variable->name(), language_mode());
      break;
    }
  }
}


void BytecodeGenerator::VisitAssignment(Assignment* expr) {
  DCHECK(expr->target()->IsValidReferenceExpression());
  Register object, key;
  Handle<String> name;

  // Left-hand side can only be a property, a global or a variable slot.
  Property* property = expr->target()->AsProperty();
  LhsKind assign_type = Property::GetAssignType(property);

  // Evaluate LHS expression.
  switch (assign_type) {
    case VARIABLE:
      // Nothing to do to evaluate variable assignment LHS.
      break;
    case NAMED_PROPERTY: {
      object = VisitForRegisterValue(property->obj());
      name = property->key()->AsLiteral()->AsPropertyName();
      break;
    }
    case KEYED_PROPERTY: {
      object = VisitForRegisterValue(property->obj());
      if (expr->is_compound()) {
        // Use VisitForAccumulator and store to register so that the key is
        // still in the accumulator for loading the old value below.
        key = execution_result()->NewRegister();
        VisitForAccumulatorValue(property->key());
        builder()->StoreAccumulatorInRegister(key);
      } else {
        key = VisitForRegisterValue(property->key());
      }
      break;
    }
    case NAMED_SUPER_PROPERTY:
    case KEYED_SUPER_PROPERTY:
      UNIMPLEMENTED();
  }

  // Evaluate the value and potentially handle compound assignments by loading
  // the left-hand side value and performing a binary operation.
  if (expr->is_compound()) {
    Register old_value;
    switch (assign_type) {
      case VARIABLE: {
        VariableProxy* proxy = expr->target()->AsVariableProxy();
        old_value = VisitVariableLoadForRegisterValue(
            proxy->var(), proxy->VariableFeedbackSlot());
        break;
      }
      case NAMED_PROPERTY: {
        FeedbackVectorSlot slot = property->PropertyFeedbackSlot();
        old_value = execution_result()->NewRegister();
        builder()
            ->LoadNamedProperty(object, name, feedback_index(slot),
                                language_mode())
            .StoreAccumulatorInRegister(old_value);
        break;
      }
      case KEYED_PROPERTY: {
        // Key is already in accumulator at this point due to evaluating the
        // LHS above.
        FeedbackVectorSlot slot = property->PropertyFeedbackSlot();
        old_value = execution_result()->NewRegister();
        builder()
            ->LoadKeyedProperty(object, feedback_index(slot), language_mode())
            .StoreAccumulatorInRegister(old_value);
        break;
      }
      case NAMED_SUPER_PROPERTY:
      case KEYED_SUPER_PROPERTY:
        UNIMPLEMENTED();
        break;
    }
    VisitForAccumulatorValue(expr->value());
    builder()->BinaryOperation(expr->binary_op(), old_value,
                               language_mode_strength());
  } else {
    VisitForAccumulatorValue(expr->value());
  }

  // Store the value.
  FeedbackVectorSlot slot = expr->AssignmentSlot();
  switch (assign_type) {
    case VARIABLE: {
      // TODO(oth): The VisitVariableAssignment() call is hard to reason about.
      // Is the value in the accumulator safe? Yes, but scary.
      Variable* variable = expr->target()->AsVariableProxy()->var();
      VisitVariableAssignment(variable, slot);
      break;
    }
    case NAMED_PROPERTY:
      builder()->StoreNamedProperty(object, name, feedback_index(slot),
                                    language_mode());
      break;
    case KEYED_PROPERTY:
      builder()->StoreKeyedProperty(object, key, feedback_index(slot),
                                    language_mode());
      break;
    case NAMED_SUPER_PROPERTY:
    case KEYED_SUPER_PROPERTY:
      UNIMPLEMENTED();
  }
  execution_result()->SetResultInAccumulator();
}


void BytecodeGenerator::VisitYield(Yield* expr) { UNIMPLEMENTED(); }


void BytecodeGenerator::VisitThrow(Throw* expr) {
  VisitForAccumulatorValue(expr->exception());
  builder()->Throw();
}


void BytecodeGenerator::VisitPropertyLoad(Register obj, Property* expr) {
  LhsKind property_kind = Property::GetAssignType(expr);
  FeedbackVectorSlot slot = expr->PropertyFeedbackSlot();
  switch (property_kind) {
    case VARIABLE:
      UNREACHABLE();
    case NAMED_PROPERTY: {
      builder()->LoadNamedProperty(obj,
                                   expr->key()->AsLiteral()->AsPropertyName(),
                                   feedback_index(slot), language_mode());
      break;
    }
    case KEYED_PROPERTY: {
      VisitForAccumulatorValue(expr->key());
      builder()->LoadKeyedProperty(obj, feedback_index(slot), language_mode());
      break;
    }
    case NAMED_SUPER_PROPERTY:
    case KEYED_SUPER_PROPERTY:
      UNIMPLEMENTED();
  }
  execution_result()->SetResultInAccumulator();
}


void BytecodeGenerator::VisitPropertyLoadForAccumulator(Register obj,
                                                        Property* expr) {
  AccumulatorResultScope result_scope(this);
  VisitPropertyLoad(obj, expr);
}


void BytecodeGenerator::VisitProperty(Property* expr) {
  Register obj = VisitForRegisterValue(expr->obj());
  VisitPropertyLoad(obj, expr);
}


Register BytecodeGenerator::VisitArguments(ZoneList<Expression*>* args) {
  if (args->length() == 0) {
    return Register();
  }

  // Visit arguments and place in a contiguous block of temporary
  // registers.  Return the first temporary register corresponding to
  // the first argument.
  //
  // NB the caller may have already called
  // PrepareForConsecutiveAllocations() with args->length() + N. The
  // second call here will be a no-op provided there have been N or
  // less calls to NextConsecutiveRegister(). Otherwise, the arguments
  // here will be consecutive, but they will not be consecutive with
  // earlier consecutive allocations made by the caller.
  execution_result()->PrepareForConsecutiveAllocations(args->length());

  // Visit for first argument that goes into returned register
  Register first_arg = execution_result()->NextConsecutiveRegister();
  VisitForAccumulatorValue(args->at(0));
  builder()->StoreAccumulatorInRegister(first_arg);

  // Visit remaining arguments
  for (int i = 1; i < static_cast<int>(args->length()); i++) {
    Register ith_arg = execution_result()->NextConsecutiveRegister();
    VisitForAccumulatorValue(args->at(i));
    builder()->StoreAccumulatorInRegister(ith_arg);
    DCHECK(ith_arg.index() - i == first_arg.index());
  }
  return first_arg;
}


void BytecodeGenerator::VisitCall(Call* expr) {
  Expression* callee_expr = expr->expression();
  Call::CallType call_type = expr->GetCallType(isolate());

  // Prepare the callee and the receiver to the function call. This depends on
  // the semantics of the underlying call type.

  // The receiver and arguments need to be allocated consecutively for
  // Call(). We allocate the callee and receiver consecutively for calls to
  // kLoadLookupSlot. Future optimizations could avoid this there are no
  // arguments or the receiver and arguments are already consecutive.
  ZoneList<Expression*>* args = expr->arguments();
  execution_result()->PrepareForConsecutiveAllocations(args->length() + 2);
  Register callee = execution_result()->NextConsecutiveRegister();
  Register receiver = execution_result()->NextConsecutiveRegister();

  switch (call_type) {
    case Call::NAMED_PROPERTY_CALL:
    case Call::KEYED_PROPERTY_CALL: {
      Property* property = callee_expr->AsProperty();
      VisitForAccumulatorValue(property->obj());
      builder()->StoreAccumulatorInRegister(receiver);
      VisitPropertyLoadForAccumulator(receiver, property);
      builder()->StoreAccumulatorInRegister(callee);
      break;
    }
    case Call::GLOBAL_CALL: {
      // Receiver is undefined for global calls.
      builder()->LoadUndefined().StoreAccumulatorInRegister(receiver);
      // Load callee as a global variable.
      VariableProxy* proxy = callee_expr->AsVariableProxy();
      VisitVariableLoadForAccumulatorValue(proxy->var(),
                                           proxy->VariableFeedbackSlot());
      builder()->StoreAccumulatorInRegister(callee);
      break;
    }
    case Call::LOOKUP_SLOT_CALL:
    case Call::POSSIBLY_EVAL_CALL: {
      if (callee_expr->AsVariableProxy()->var()->IsLookupSlot()) {
        TemporaryRegisterScope temporary_register_scope(builder());
        temporary_register_scope.PrepareForConsecutiveAllocations(2);
        Register context = temporary_register_scope.NextConsecutiveRegister();
        Register name = temporary_register_scope.NextConsecutiveRegister();

        // Call LoadLookupSlot to get the callee and receiver.
        DCHECK(Register::AreContiguous(callee, receiver));
        Variable* variable = callee_expr->AsVariableProxy()->var();
        builder()
            ->MoveRegister(Register::function_context(), context)
            .LoadLiteral(variable->name())
            .StoreAccumulatorInRegister(name)
            .CallRuntimeForPair(Runtime::kLoadLookupSlot, context, 2, callee);
        break;
      }
      // Fall through.
      DCHECK_EQ(call_type, Call::POSSIBLY_EVAL_CALL);
    }
    case Call::OTHER_CALL: {
      builder()->LoadUndefined().StoreAccumulatorInRegister(receiver);
      VisitForAccumulatorValue(callee_expr);
      builder()->StoreAccumulatorInRegister(callee);
      break;
    }
    case Call::NAMED_SUPER_PROPERTY_CALL:
    case Call::KEYED_SUPER_PROPERTY_CALL:
    case Call::SUPER_CALL:
      UNIMPLEMENTED();
  }

  // Evaluate all arguments to the function call and store in sequential
  // registers.
  Register arg = VisitArguments(args);
  CHECK(args->length() == 0 || arg.index() == receiver.index() + 1);

  // Resolve callee for a potential direct eval call. This block will mutate the
  // callee value.
  if (call_type == Call::POSSIBLY_EVAL_CALL && args->length() > 0) {
    TemporaryRegisterScope temporary_register_scope(builder());
    temporary_register_scope.PrepareForConsecutiveAllocations(5);
    Register callee_for_eval =
        temporary_register_scope.NextConsecutiveRegister();
    Register source = temporary_register_scope.NextConsecutiveRegister();
    Register function = temporary_register_scope.NextConsecutiveRegister();
    Register language = temporary_register_scope.NextConsecutiveRegister();
    Register position = temporary_register_scope.NextConsecutiveRegister();

    // Set up arguments for ResolvePossiblyDirectEval by copying callee, source
    // strings and function closure, and loading language and
    // position.
    builder()
        ->MoveRegister(callee, callee_for_eval)
        .MoveRegister(arg, source)
        .MoveRegister(Register::function_closure(), function)
        .LoadLiteral(Smi::FromInt(language_mode()))
        .StoreAccumulatorInRegister(language)
        .LoadLiteral(
            Smi::FromInt(execution_context()->scope()->start_position()))
        .StoreAccumulatorInRegister(position);

    // Call ResolvePossiblyDirectEval and modify the callee.
    builder()
        ->CallRuntime(Runtime::kResolvePossiblyDirectEval, callee_for_eval, 5)
        .StoreAccumulatorInRegister(callee);
  }

  // TODO(rmcilroy): Use CallIC to allow call type feedback.
  builder()->Call(callee, receiver, args->length(),
                  feedback_index(expr->CallFeedbackICSlot()));
  execution_result()->SetResultInAccumulator();
}


void BytecodeGenerator::VisitCallNew(CallNew* expr) {
  Register constructor = execution_result()->NewRegister();
  VisitForAccumulatorValue(expr->expression());
  builder()->StoreAccumulatorInRegister(constructor);

  ZoneList<Expression*>* args = expr->arguments();
  Register first_arg = VisitArguments(args);
  builder()->New(constructor, first_arg, args->length());
  execution_result()->SetResultInAccumulator();
}


void BytecodeGenerator::VisitCallRuntime(CallRuntime* expr) {
  ZoneList<Expression*>* args = expr->arguments();
  Register receiver;
  if (expr->is_jsruntime()) {
    // Allocate a register for the receiver and load it with undefined.
    execution_result()->PrepareForConsecutiveAllocations(args->length() + 1);
    receiver = execution_result()->NextConsecutiveRegister();
    builder()->LoadUndefined().StoreAccumulatorInRegister(receiver);
  }
  // Evaluate all arguments to the runtime call.
  Register first_arg = VisitArguments(args);

  if (expr->is_jsruntime()) {
    DCHECK(args->length() == 0 || first_arg.index() == receiver.index() + 1);
    builder()->CallJSRuntime(expr->context_index(), receiver, args->length());
  } else {
    Runtime::FunctionId function_id = expr->function()->function_id;
    builder()->CallRuntime(function_id, first_arg, args->length());
  }
  execution_result()->SetResultInAccumulator();
}


void BytecodeGenerator::VisitVoid(UnaryOperation* expr) {
  VisitForEffect(expr->expression());
  builder()->LoadUndefined();
  execution_result()->SetResultInAccumulator();
}


void BytecodeGenerator::VisitTypeOf(UnaryOperation* expr) {
  if (expr->expression()->IsVariableProxy()) {
    // Typeof does not throw a reference error on global variables, hence we
    // perform a non-contextual load in case the operand is a variable proxy.
    VariableProxy* proxy = expr->expression()->AsVariableProxy();
    VisitVariableLoadForAccumulatorValue(
        proxy->var(), proxy->VariableFeedbackSlot(), INSIDE_TYPEOF);
  } else {
    VisitForAccumulatorValue(expr->expression());
  }
  builder()->TypeOf();
  execution_result()->SetResultInAccumulator();
}


void BytecodeGenerator::VisitNot(UnaryOperation* expr) {
  VisitForAccumulatorValue(expr->expression());
  builder()->LogicalNot();
  execution_result()->SetResultInAccumulator();
}


void BytecodeGenerator::VisitUnaryOperation(UnaryOperation* expr) {
  switch (expr->op()) {
    case Token::Value::NOT:
      VisitNot(expr);
      break;
    case Token::Value::TYPEOF:
      VisitTypeOf(expr);
      break;
    case Token::Value::VOID:
      VisitVoid(expr);
      break;
    case Token::Value::DELETE:
      VisitDelete(expr);
      break;
    case Token::Value::BIT_NOT:
    case Token::Value::ADD:
    case Token::Value::SUB:
      // These operators are converted to an equivalent binary operators in
      // the parser. These operators are not expected to be visited here.
      UNREACHABLE();
    default:
      UNREACHABLE();
  }
}


void BytecodeGenerator::VisitDelete(UnaryOperation* expr) {
  if (expr->expression()->IsProperty()) {
    // Delete of an object property is allowed both in sloppy
    // and strict modes.
    Property* property = expr->expression()->AsProperty();
    Register object = VisitForRegisterValue(property->obj());
    VisitForAccumulatorValue(property->key());
    builder()->Delete(object, language_mode());
  } else if (expr->expression()->IsVariableProxy()) {
    // Delete of an unqualified identifier is allowed in sloppy mode but is
    // not allowed in strict mode. Deleting 'this' is allowed in both modes.
    VariableProxy* proxy = expr->expression()->AsVariableProxy();
    Variable* variable = proxy->var();
    DCHECK(is_sloppy(language_mode()) || variable->HasThisName(isolate()));
    switch (variable->location()) {
      case VariableLocation::GLOBAL:
      case VariableLocation::UNALLOCATED: {
        // Global var, let, const or variables not explicitly declared.
        Register native_context = execution_result()->NewRegister();
        Register global_object = execution_result()->NewRegister();
        builder()
            ->LoadContextSlot(execution_context()->reg(),
                              Context::NATIVE_CONTEXT_INDEX)
            .StoreAccumulatorInRegister(native_context)
            .LoadContextSlot(native_context, Context::EXTENSION_INDEX)
            .StoreAccumulatorInRegister(global_object)
            .LoadLiteral(variable->name())
            .Delete(global_object, language_mode());
        break;
      }
      case VariableLocation::PARAMETER:
      case VariableLocation::LOCAL:
      case VariableLocation::CONTEXT: {
        // Deleting local var/let/const, context variables, and arguments
        // does not have any effect.
        if (variable->HasThisName(isolate())) {
          builder()->LoadTrue();
        } else {
          builder()->LoadFalse();
        }
        break;
      }
      case VariableLocation::LOOKUP: {
        builder()->LoadLiteral(variable->name()).DeleteLookupSlot();
        break;
      }
      default:
        UNREACHABLE();
    }
  } else {
    // Delete of an unresolvable reference returns true.
    VisitForEffect(expr->expression());
    builder()->LoadTrue();
  }
  execution_result()->SetResultInAccumulator();
}


void BytecodeGenerator::VisitCountOperation(CountOperation* expr) {
  DCHECK(expr->expression()->IsValidReferenceExpressionOrThis());

  // Left-hand side can only be a property, a global or a variable slot.
  Property* property = expr->expression()->AsProperty();
  LhsKind assign_type = Property::GetAssignType(property);

  // TODO(rmcilroy): Set is_postfix to false if visiting for effect.
  bool is_postfix = expr->is_postfix();

  // Evaluate LHS expression and get old value.
  Register obj, key, old_value;
  Handle<String> name;
  switch (assign_type) {
    case VARIABLE: {
      VariableProxy* proxy = expr->expression()->AsVariableProxy();
      VisitVariableLoadForAccumulatorValue(proxy->var(),
                                           proxy->VariableFeedbackSlot());
      break;
    }
    case NAMED_PROPERTY: {
      FeedbackVectorSlot slot = property->PropertyFeedbackSlot();
      obj = VisitForRegisterValue(property->obj());
      name = property->key()->AsLiteral()->AsPropertyName();
      builder()->LoadNamedProperty(obj, name, feedback_index(slot),
                                   language_mode());
      break;
    }
    case KEYED_PROPERTY: {
      FeedbackVectorSlot slot = property->PropertyFeedbackSlot();
      obj = VisitForRegisterValue(property->obj());
      // Use visit for accumulator here since we need the key in the accumulator
      // for the LoadKeyedProperty.
      key = execution_result()->NewRegister();
      VisitForAccumulatorValue(property->key());
      builder()->StoreAccumulatorInRegister(key).LoadKeyedProperty(
          obj, feedback_index(slot), language_mode());
      break;
    }
    case NAMED_SUPER_PROPERTY:
    case KEYED_SUPER_PROPERTY:
      UNIMPLEMENTED();
  }

  // Convert old value into a number.
  if (!is_strong(language_mode())) {
    builder()->CastAccumulatorToNumber();
  }

  // Save result for postfix expressions.
  if (is_postfix) {
    old_value = execution_result()->outer()->NewRegister();
    builder()->StoreAccumulatorInRegister(old_value);
  }

  // Perform +1/-1 operation.
  builder()->CountOperation(expr->binary_op(), language_mode_strength());

  // Store the value.
  FeedbackVectorSlot feedback_slot = expr->CountSlot();
  switch (assign_type) {
    case VARIABLE: {
      Variable* variable = expr->expression()->AsVariableProxy()->var();
      VisitVariableAssignment(variable, feedback_slot);
      break;
    }
    case NAMED_PROPERTY: {
      builder()->StoreNamedProperty(obj, name, feedback_index(feedback_slot),
                                    language_mode());
      break;
    }
    case KEYED_PROPERTY: {
      builder()->StoreKeyedProperty(obj, key, feedback_index(feedback_slot),
                                    language_mode());
      break;
    }
    case NAMED_SUPER_PROPERTY:
    case KEYED_SUPER_PROPERTY:
      UNIMPLEMENTED();
  }

  // Restore old value for postfix expressions.
  if (is_postfix) {
    execution_result()->SetResultInRegister(old_value);
  } else {
    execution_result()->SetResultInAccumulator();
  }
}


void BytecodeGenerator::VisitBinaryOperation(BinaryOperation* binop) {
  switch (binop->op()) {
    case Token::COMMA:
      VisitCommaExpression(binop);
      break;
    case Token::OR:
      VisitLogicalOrExpression(binop);
      break;
    case Token::AND:
      VisitLogicalAndExpression(binop);
      break;
    default:
      VisitArithmeticExpression(binop);
      break;
  }
}


void BytecodeGenerator::VisitCompareOperation(CompareOperation* expr) {
  // The evaluation of binary comparison expressions has an assignment
  // hazard because the lhs may be a variable that evaluates to a
  // local or parameter and the rhs may modify that, e.g. y = x + (x = 1)
  // To get a correct result the generator treats the inner assigment
  // as being made to a temporary x' that is spilled on exit of the
  // assignment hazard.
  AssignmentHazardScope assignment_hazard_scope(this);

  Register lhs = VisitForRegisterValue(expr->left());
  VisitForAccumulatorValue(expr->right());
  builder()->CompareOperation(expr->op(), lhs, language_mode_strength());
  execution_result()->SetResultInAccumulator();
}


void BytecodeGenerator::VisitArithmeticExpression(BinaryOperation* expr) {
  // The evaluation of binary arithmetic expressions has an assignment
  // hazard because the lhs may be a variable that evaluates to a
  // local or parameter and the rhs may modify that, e.g. y = x + (x = 1)
  // To get a correct result the generator treats the inner assigment
  // as being made to a temporary x' that is spilled on exit of the
  // assignment hazard.
  AssignmentHazardScope assignment_hazard_scope(this);

  Register lhs = VisitForRegisterValue(expr->left());
  VisitForAccumulatorValue(expr->right());
  builder()->BinaryOperation(expr->op(), lhs, language_mode_strength());
  execution_result()->SetResultInAccumulator();
}


void BytecodeGenerator::VisitSpread(Spread* expr) { UNREACHABLE(); }


void BytecodeGenerator::VisitEmptyParentheses(EmptyParentheses* expr) {
  UNREACHABLE();
}


void BytecodeGenerator::VisitThisFunction(ThisFunction* expr) {
  execution_result()->SetResultInRegister(Register::function_closure());
}


void BytecodeGenerator::VisitSuperCallReference(SuperCallReference* expr) {
  UNIMPLEMENTED();
}


void BytecodeGenerator::VisitSuperPropertyReference(
    SuperPropertyReference* expr) {
  UNIMPLEMENTED();
}


void BytecodeGenerator::VisitCommaExpression(BinaryOperation* binop) {
  VisitForEffect(binop->left());
  Visit(binop->right());
}


void BytecodeGenerator::VisitLogicalOrExpression(BinaryOperation* binop) {
  Expression* left = binop->left();
  Expression* right = binop->right();

  // Short-circuit evaluation- If it is known that left is always true,
  // no need to visit right
  if (left->ToBooleanIsTrue()) {
    VisitForAccumulatorValue(left);
  } else {
    BytecodeLabel end_label;
    VisitForAccumulatorValue(left);
    builder()->JumpIfTrue(&end_label);
    VisitForAccumulatorValue(right);
    builder()->Bind(&end_label);
  }
  execution_result()->SetResultInAccumulator();
}


void BytecodeGenerator::VisitLogicalAndExpression(BinaryOperation* binop) {
  Expression* left = binop->left();
  Expression* right = binop->right();

  // Short-circuit evaluation- If it is known that left is always false,
  // no need to visit right
  if (left->ToBooleanIsFalse()) {
    VisitForAccumulatorValue(left);
  } else {
    BytecodeLabel end_label;
    VisitForAccumulatorValue(left);
    builder()->JumpIfFalse(&end_label);
    VisitForAccumulatorValue(right);
    builder()->Bind(&end_label);
  }
  execution_result()->SetResultInAccumulator();
}


void BytecodeGenerator::VisitRewritableAssignmentExpression(
    RewritableAssignmentExpression* expr) {
  Visit(expr->expression());
}


void BytecodeGenerator::VisitNewLocalFunctionContext() {
  AccumulatorResultScope accumulator_execution_result(this);
  Scope* scope = this->scope();

  // Allocate a new local context.
  if (scope->is_script_scope()) {
    TemporaryRegisterScope temporary_register_scope(builder());
    Register closure = temporary_register_scope.NewRegister();
    Register scope_info = temporary_register_scope.NewRegister();
    DCHECK(Register::AreContiguous(closure, scope_info));
    builder()
        ->LoadAccumulatorWithRegister(Register::function_closure())
        .StoreAccumulatorInRegister(closure)
        .LoadLiteral(scope->GetScopeInfo(isolate()))
        .StoreAccumulatorInRegister(scope_info)
        .CallRuntime(Runtime::kNewScriptContext, closure, 2);
  } else {
    builder()->CallRuntime(Runtime::kNewFunctionContext,
                           Register::function_closure(), 1);
  }
  execution_result()->SetResultInAccumulator();
}


void BytecodeGenerator::VisitBuildLocalActivationContext() {
  Scope* scope = this->scope();

  if (scope->has_this_declaration() && scope->receiver()->IsContextSlot()) {
    Variable* variable = scope->receiver();
    Register receiver(builder()->Parameter(0));
    // Context variable (at bottom of the context chain).
    DCHECK_EQ(0, scope->ContextChainLength(variable->scope()));
    builder()->LoadAccumulatorWithRegister(receiver).StoreContextSlot(
        execution_context()->reg(), variable->index());
  }

  // Copy parameters into context if necessary.
  int num_parameters = scope->num_parameters();
  for (int i = 0; i < num_parameters; i++) {
    Variable* variable = scope->parameter(i);
    if (!variable->IsContextSlot()) continue;

    // The parameter indices are shifted by 1 (receiver is variable
    // index -1 but is parameter index 0 in BytecodeArrayBuilder).
    Register parameter(builder()->Parameter(i + 1));
    // Context variable (at bottom of the context chain).
    DCHECK_EQ(0, scope->ContextChainLength(variable->scope()));
    builder()->LoadAccumulatorWithRegister(parameter)
        .StoreContextSlot(execution_context()->reg(), variable->index());
  }
}


void BytecodeGenerator::VisitNewLocalBlockContext(Scope* scope) {
  AccumulatorResultScope accumulator_execution_result(this);
  DCHECK(scope->is_block_scope());

  // Allocate a new local block context.
  TemporaryRegisterScope temporary_register_scope(builder());
  temporary_register_scope.PrepareForConsecutiveAllocations(2);
  Register scope_info = temporary_register_scope.NextConsecutiveRegister();
  Register closure = temporary_register_scope.NextConsecutiveRegister();

  builder()
      ->LoadLiteral(scope->GetScopeInfo(isolate()))
      .StoreAccumulatorInRegister(scope_info);
  VisitFunctionClosureForContext();
  builder()
      ->StoreAccumulatorInRegister(closure)
      .CallRuntime(Runtime::kPushBlockContext, scope_info, 2);
  execution_result()->SetResultInAccumulator();
}


void BytecodeGenerator::VisitObjectLiteralAccessor(
    Register home_object, ObjectLiteralProperty* property, Register value_out) {
  // TODO(rmcilroy): Replace value_out with VisitForRegister();
  if (property == nullptr) {
    builder()->LoadNull().StoreAccumulatorInRegister(value_out);
  } else {
    VisitForAccumulatorValue(property->value());
    builder()->StoreAccumulatorInRegister(value_out);
    VisitSetHomeObject(value_out, home_object, property);
  }
}


void BytecodeGenerator::VisitSetHomeObject(Register value, Register home_object,
                                           ObjectLiteralProperty* property,
                                           int slot_number) {
  Expression* expr = property->value();
  if (!FunctionLiteral::NeedsHomeObject(expr)) return;

  UNIMPLEMENTED();
}


void BytecodeGenerator::VisitArgumentsObject(Variable* variable) {
  if (variable == nullptr) return;

  DCHECK(variable->IsContextSlot() || variable->IsStackAllocated());

  // Allocate and initialize a new arguments object and assign to the
  // {arguments} variable.
  CreateArgumentsType type =
      is_strict(language_mode()) || !info()->has_simple_parameters()
          ? CreateArgumentsType::kUnmappedArguments
          : CreateArgumentsType::kMappedArguments;
  builder()->CreateArguments(type);
  VisitVariableAssignment(variable, FeedbackVectorSlot::Invalid());
}


void BytecodeGenerator::VisitThisFunctionVariable(Variable* variable) {
  if (variable == nullptr) return;

  // TODO(rmcilroy): Remove once we have tests which exercise this code path.
  UNIMPLEMENTED();

  // Store the closure we were called with in the given variable.
  builder()->LoadAccumulatorWithRegister(Register::function_closure());
  VisitVariableAssignment(variable, FeedbackVectorSlot::Invalid());
}


void BytecodeGenerator::VisitNewTargetVariable(Variable* variable) {
  if (variable == nullptr) return;

  // Store the new target we were called with in the given variable.
  builder()->LoadAccumulatorWithRegister(Register::new_target());
  VisitVariableAssignment(variable, FeedbackVectorSlot::Invalid());
}


void BytecodeGenerator::VisitFunctionClosureForContext() {
  AccumulatorResultScope accumulator_execution_result(this);
  Scope* closure_scope = execution_context()->scope()->ClosureScope();
  if (closure_scope->is_script_scope() ||
      closure_scope->is_module_scope()) {
    // Contexts nested in the native context have a canonical empty function as
    // their closure, not the anonymous closure containing the global code.
    Register native_context = execution_result()->NewRegister();
    builder()
        ->LoadContextSlot(execution_context()->reg(),
                          Context::NATIVE_CONTEXT_INDEX)
        .StoreAccumulatorInRegister(native_context)
        .LoadContextSlot(native_context, Context::CLOSURE_INDEX);
  } else {
    DCHECK(closure_scope->is_function_scope());
    builder()->LoadAccumulatorWithRegister(Register::function_closure());
  }
  execution_result()->SetResultInAccumulator();
}


// Visits the expression |expr| and places the result in the accumulator.
void BytecodeGenerator::VisitForAccumulatorValue(Expression* expr) {
  AccumulatorResultScope accumulator_scope(this);
  Visit(expr);
}


// Visits the expression |expr| and discards the result.
void BytecodeGenerator::VisitForEffect(Expression* expr) {
  EffectResultScope effect_scope(this);
  Visit(expr);
}


// Visits the expression |expr| and returns the register containing
// the expression result.
Register BytecodeGenerator::VisitForRegisterValue(Expression* expr) {
  RegisterResultScope register_scope(this);
  Visit(expr);
  return register_scope.ResultRegister();
}


Register BytecodeGenerator::NextContextRegister() const {
  if (execution_context() == nullptr) {
    // Return the incoming function context for the outermost execution context.
    return Register::function_context();
  }
  Register previous = execution_context()->reg();
  if (previous == Register::function_context()) {
    // If the previous context was the incoming function context, then the next
    // context register is the first local context register.
    return builder_.first_context_register();
  } else {
    // Otherwise use the next local context register.
    DCHECK_LT(previous.index(), builder_.last_context_register().index());
    return Register(previous.index() + 1);
  }
}


LanguageMode BytecodeGenerator::language_mode() const {
  return info()->language_mode();
}


Strength BytecodeGenerator::language_mode_strength() const {
  return strength(language_mode());
}


int BytecodeGenerator::feedback_index(FeedbackVectorSlot slot) const {
  return info()->feedback_vector()->GetIndex(slot);
}

}  // namespace interpreter
}  // namespace internal
}  // namespace v8