CSE2410 Fall 2014 Bounce

// 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.

#include "v8.h"

#include "scopes.h"

#include "accessors.h"

#include "bootstrapper.h"

#include "compiler.h"

#include "messages.h"

#include "scopeinfo.h"

#include "allocation-inl.h"

namespace v8 {

namespace internal {

// ----------------------------------------------------------------------------

// Implementation of LocalsMap

//

// Note: We are storing the handle locations as key values in the hash map.

//       When inserting a new variable via Declare(), we rely on the fact that

//       the handle location remains alive for the duration of that variable

//       use. Because a Variable holding a handle with the same location exists

//       this is ensured.

static bool Match(void* key1, void* key2) {

  String* name1 = *reinterpret_cast<String**>(key1);

  String* name2 = *reinterpret_cast<String**>(key2);

  ASSERT(name1->IsInternalizedString());

  ASSERT(name2->IsInternalizedString());

  return name1 == name2;

}

VariableMap::VariableMap(Zone* zone)

    : ZoneHashMap(Match, 8, ZoneAllocationPolicy(zone)),

      zone_(zone) {}

VariableMap::~VariableMap() {}

Variable* VariableMap::Declare(

    Scope* scope,

    Handle<String> name,

    VariableMode mode,

    bool is_valid_lhs,

    Variable::Kind kind,

    InitializationFlag initialization_flag,

    Interface* interface) {

  Entry* p = ZoneHashMap::Lookup(name.location(), name->Hash(), true,

                                 ZoneAllocationPolicy(zone()));

  if (p->value == NULL) {

    // The variable has not been declared yet -> insert it.

    ASSERT(p->key == name.location());

    p->value = new(zone()) Variable(scope,

                                    name,

                                    mode,

                                    is_valid_lhs,

                                    kind,

                                    initialization_flag,

                                    interface);

  }

  return reinterpret_cast<Variable*>(p->value);

}

Variable* VariableMap::Lookup(Handle<String> name) {

  Entry* p = ZoneHashMap::Lookup(name.location(), name->Hash(), false,

                                 ZoneAllocationPolicy(NULL));

  if (p != NULL) {

    ASSERT(*reinterpret_cast<String**>(p->key) == *name);

    ASSERT(p->value != NULL);

    return reinterpret_cast<Variable*>(p->value);

  }

  return NULL;

}

// ----------------------------------------------------------------------------

// Implementation of Scope

Scope::Scope(Scope* outer_scope, ScopeType scope_type, Zone* zone)

    : isolate_(zone->isolate()),

      inner_scopes_(4, zone),

      variables_(zone),

      internals_(4, zone),

      temps_(4, zone),

      params_(4, zone),

      unresolved_(16, zone),

      decls_(4, zone),

      interface_(FLAG_harmony_modules &&

                 (scope_type == MODULE_SCOPE || scope_type == GLOBAL_SCOPE)

                     ? Interface::NewModule(zone) : NULL),

      already_resolved_(false),

      zone_(zone) {

  SetDefaults(scope_type, outer_scope, Handle<ScopeInfo>::null());

  // The outermost scope must be a global scope.

  ASSERT(scope_type == GLOBAL_SCOPE || outer_scope != NULL);

  ASSERT(!HasIllegalRedeclaration());

}

Scope::Scope(Scope* inner_scope,

             ScopeType scope_type,

             Handle<ScopeInfo> scope_info,

             Zone* zone)

    : isolate_(zone->isolate()),

      inner_scopes_(4, zone),

      variables_(zone),

      internals_(4, zone),

      temps_(4, zone),

      params_(4, zone),

      unresolved_(16, zone),

      decls_(4, zone),

      interface_(NULL),

      already_resolved_(true),

      zone_(zone) {

  SetDefaults(scope_type, NULL, scope_info);

  if (!scope_info.is_null()) {

    num_heap_slots_ = scope_info_->ContextLength();

  }

  // Ensure at least MIN_CONTEXT_SLOTS to indicate a materialized context.

  num_heap_slots_ = Max(num_heap_slots_,

                        static_cast<int>(Context::MIN_CONTEXT_SLOTS));

  AddInnerScope(inner_scope);

}

Scope::Scope(Scope* inner_scope, Handle<String> catch_variable_name, Zone* zone)

    : isolate_(zone->isolate()),

      inner_scopes_(1, zone),

      variables_(zone),

      internals_(0, zone),

      temps_(0, zone),

      params_(0, zone),

      unresolved_(0, zone),

      decls_(0, zone),

      interface_(NULL),

      already_resolved_(true),

      zone_(zone) {

  SetDefaults(CATCH_SCOPE, NULL, Handle<ScopeInfo>::null());

  AddInnerScope(inner_scope);

  ++num_var_or_const_;

  num_heap_slots_ = Context::MIN_CONTEXT_SLOTS;

  Variable* variable = variables_.Declare(this,

                                          catch_variable_name,

                                          VAR,

                                          true,  // Valid left-hand side.

                                          Variable::NORMAL,

                                          kCreatedInitialized);

  AllocateHeapSlot(variable);

}

void Scope::SetDefaults(ScopeType scope_type,

                        Scope* outer_scope,

                        Handle<ScopeInfo> scope_info) {

  outer_scope_ = outer_scope;

  scope_type_ = scope_type;

  scope_name_ = isolate_->factory()->empty_string();

  dynamics_ = NULL;

  receiver_ = NULL;

  function_ = NULL;

  arguments_ = NULL;

  illegal_redecl_ = NULL;

  scope_inside_with_ = false;

  scope_contains_with_ = false;

  scope_calls_eval_ = false;

  // Inherit the strict mode from the parent scope.

  language_mode_ = (outer_scope != NULL)

      ? outer_scope->language_mode_ : CLASSIC_MODE;

  outer_scope_calls_non_strict_eval_ = false;

  inner_scope_calls_eval_ = false;

  force_eager_compilation_ = false;

  force_context_allocation_ = (outer_scope != NULL && !is_function_scope())

      ? outer_scope->has_forced_context_allocation() : false;

  num_var_or_const_ = 0;

  num_stack_slots_ = 0;

  num_heap_slots_ = 0;

  num_modules_ = 0;

  module_var_ = NULL,

  scope_info_ = scope_info;

  start_position_ = RelocInfo::kNoPosition;

  end_position_ = RelocInfo::kNoPosition;

  if (!scope_info.is_null()) {

    scope_calls_eval_ = scope_info->CallsEval();

    language_mode_ = scope_info->language_mode();

  }

}

Scope* Scope::DeserializeScopeChain(Context* context, Scope* global_scope,

                                    Zone* zone) {

  // Reconstruct the outer scope chain from a closure's context chain.

  Scope* current_scope = NULL;

  Scope* innermost_scope = NULL;

  bool contains_with = false;

  while (!context->IsNativeContext()) {

    if (context->IsWithContext()) {

      Scope* with_scope = new(zone) Scope(current_scope,

                                          WITH_SCOPE,

                                          Handle<ScopeInfo>::null(),

                                          zone);

      current_scope = with_scope;

      // All the inner scopes are inside a with.

      contains_with = true;

      for (Scope* s = innermost_scope; s != NULL; s = s->outer_scope()) {

        s->scope_inside_with_ = true;

      }

    } else if (context->IsGlobalContext()) {

      ScopeInfo* scope_info = ScopeInfo::cast(context->extension());

      current_scope = new(zone) Scope(current_scope,

                                      GLOBAL_SCOPE,

                                      Handle<ScopeInfo>(scope_info),

                                      zone);

    } else if (context->IsModuleContext()) {

      ScopeInfo* scope_info = ScopeInfo::cast(context->module()->scope_info());

      current_scope = new(zone) Scope(current_scope,

                                      MODULE_SCOPE,

                                      Handle<ScopeInfo>(scope_info),

                                      zone);

    } else if (context->IsFunctionContext()) {

      ScopeInfo* scope_info = context->closure()->shared()->scope_info();

      current_scope = new(zone) Scope(current_scope,

                                      FUNCTION_SCOPE,

                                      Handle<ScopeInfo>(scope_info),

                                      zone);

    } else if (context->IsBlockContext()) {

      ScopeInfo* scope_info = ScopeInfo::cast(context->extension());

      current_scope = new(zone) Scope(current_scope,

                                      BLOCK_SCOPE,

                                      Handle<ScopeInfo>(scope_info),

                                      zone);

    } else {

      ASSERT(context->IsCatchContext());

      String* name = String::cast(context->extension());

      current_scope = new(zone) Scope(

          current_scope, Handle<String>(name), zone);

    }

    if (contains_with) current_scope->RecordWithStatement();

    if (innermost_scope == NULL) innermost_scope = current_scope;

    // Forget about a with when we move to a context for a different function.

    if (context->previous()->closure() != context->closure()) {

      contains_with = false;

    }

    context = context->previous();

  }

  global_scope->AddInnerScope(current_scope);

  global_scope->PropagateScopeInfo(false);

  return (innermost_scope == NULL) ? global_scope : innermost_scope;

}

bool Scope::Analyze(CompilationInfo* info) {

  ASSERT(info->function() != NULL);

  Scope* scope = info->function()->scope();

  Scope* top = scope;

  // Traverse the scope tree up to the first unresolved scope or the global

  // scope and start scope resolution and variable allocation from that scope.

  while (!top->is_global_scope() &&

         !top->outer_scope()->already_resolved()) {

    top = top->outer_scope();

  }

  // Allocate the variables.

  {

    AstNodeFactory<AstNullVisitor> ast_node_factory(info->isolate(),

                                                    info->zone());

    if (!top->AllocateVariables(info, &ast_node_factory)) return false;

  }

#ifdef DEBUG

  if (info->isolate()->bootstrapper()->IsActive()

          ? FLAG_print_builtin_scopes

          : FLAG_print_scopes) {

    scope->Print();

  }

  if (FLAG_harmony_modules && FLAG_print_interfaces && top->is_global_scope()) {

    PrintF("global : ");

    top->interface()->Print();

  }

#endif

  info->SetScope(scope);

  return true;

}

void Scope::Initialize() {

  ASSERT(!already_resolved());

  // Add this scope as a new inner scope of the outer scope.

  if (outer_scope_ != NULL) {

    outer_scope_->inner_scopes_.Add(this, zone());

    scope_inside_with_ = outer_scope_->scope_inside_with_ || is_with_scope();

  } else {

    scope_inside_with_ = is_with_scope();

  }

  // Declare convenience variables.

  // Declare and allocate receiver (even for the global scope, and even

  // if naccesses_ == 0).

  // NOTE: When loading parameters in the global scope, we must take

  // care not to access them as properties of the global object, but

  // instead load them directly from the stack. Currently, the only

  // such parameter is 'this' which is passed on the stack when

  // invoking scripts

  if (is_declaration_scope()) {

    Variable* var =

        variables_.Declare(this,

                           isolate_->factory()->this_string(),

                           VAR,

                           false,

                           Variable::THIS,

                           kCreatedInitialized);

    var->AllocateTo(Variable::PARAMETER, -1);

    receiver_ = var;

  } else {

    ASSERT(outer_scope() != NULL);

    receiver_ = outer_scope()->receiver();

  }

  if (is_function_scope()) {

    // Declare 'arguments' variable which exists in all functions.

    // Note that it might never be accessed, in which case it won't be

    // allocated during variable allocation.

    variables_.Declare(this,

                       isolate_->factory()->arguments_string(),

                       VAR,

                       true,

                       Variable::ARGUMENTS,

                       kCreatedInitialized);

  }

}

Scope* Scope::FinalizeBlockScope() {

  ASSERT(is_block_scope());

  ASSERT(internals_.is_empty());

  ASSERT(temps_.is_empty());

  ASSERT(params_.is_empty());

  if (num_var_or_const() > 0) return this;

  // Remove this scope from outer scope.

  for (int i = 0; i < outer_scope_->inner_scopes_.length(); i++) {

    if (outer_scope_->inner_scopes_[i] == this) {

      outer_scope_->inner_scopes_.Remove(i);

      break;

    }

  }

  // Reparent inner scopes.

  for (int i = 0; i < inner_scopes_.length(); i++) {

    outer_scope()->AddInnerScope(inner_scopes_[i]);

  }

  // Move unresolved variables

  for (int i = 0; i < unresolved_.length(); i++) {

    outer_scope()->unresolved_.Add(unresolved_[i], zone());

  }

  return NULL;

}

Variable* Scope::LocalLookup(Handle<String> name) {

  Variable* result = variables_.Lookup(name);

  if (result != NULL || scope_info_.is_null()) {

    return result;

  }

  // If we have a serialized scope info, we might find the variable there.

  // There should be no local slot with the given name.

  ASSERT(scope_info_->StackSlotIndex(*name) < 0);

  // Check context slot lookup.

  VariableMode mode;

  Variable::Location location = Variable::CONTEXT;

  InitializationFlag init_flag;

  int index = scope_info_->ContextSlotIndex(*name, &mode, &init_flag);

  if (index < 0) {

    // Check parameters.

    index = scope_info_->ParameterIndex(*name);

    if (index < 0) return NULL;

    mode = DYNAMIC;

    location = Variable::LOOKUP;

    init_flag = kCreatedInitialized;

  }

  Variable* var = variables_.Declare(this, name, mode, true, Variable::NORMAL,

                                     init_flag);

  var->AllocateTo(location, index);

  return var;

}

Variable* Scope::LookupFunctionVar(Handle<String> name,

                                   AstNodeFactory<AstNullVisitor>* factory) {

  if (function_ != NULL && function_->proxy()->name().is_identical_to(name)) {

    return function_->proxy()->var();

  } else if (!scope_info_.is_null()) {

    // If we are backed by a scope info, try to lookup the variable there.

    VariableMode mode;

    int index = scope_info_->FunctionContextSlotIndex(*name, &mode);

    if (index < 0) return NULL;

    Variable* var = new(zone()) Variable(

        this, name, mode, true /* is valid LHS */,

        Variable::NORMAL, kCreatedInitialized);

    VariableProxy* proxy = factory->NewVariableProxy(var);

    VariableDeclaration* declaration = factory->NewVariableDeclaration(

        proxy, mode, this, RelocInfo::kNoPosition);

    DeclareFunctionVar(declaration);

    var->AllocateTo(Variable::CONTEXT, index);

    return var;

  } else {

    return NULL;

  }

}

Variable* Scope::Lookup(Handle<String> name) {

  for (Scope* scope = this;

       scope != NULL;

       scope = scope->outer_scope()) {

    Variable* var = scope->LocalLookup(name);

    if (var != NULL) return var;

  }

  return NULL;

}

void Scope::DeclareParameter(Handle<String> name, VariableMode mode) {

  ASSERT(!already_resolved());

  ASSERT(is_function_scope());

  Variable* var = variables_.Declare(this, name, mode, true, Variable::NORMAL,

                                     kCreatedInitialized);

  params_.Add(var, zone());

}

Variable* Scope::DeclareLocal(Handle<String> name,

                              VariableMode mode,

                              InitializationFlag init_flag,

                              Interface* interface) {

  ASSERT(!already_resolved());

  // This function handles VAR and CONST modes.  DYNAMIC variables are

  // introduces during variable allocation, INTERNAL variables are allocated

  // explicitly, and TEMPORARY variables are allocated via NewTemporary().

  ASSERT(IsDeclaredVariableMode(mode));

  ++num_var_or_const_;

  return variables_.Declare(

      this, name, mode, true, Variable::NORMAL, init_flag, interface);

}

Variable* Scope::DeclareDynamicGlobal(Handle<String> name) {

  ASSERT(is_global_scope());

  return variables_.Declare(this,

                            name,

                            DYNAMIC_GLOBAL,

                            true,

                            Variable::NORMAL,

                            kCreatedInitialized);

}

void Scope::RemoveUnresolved(VariableProxy* var) {

  // Most likely (always?) any variable we want to remove

  // was just added before, so we search backwards.

  for (int i = unresolved_.length(); i-- > 0;) {

    if (unresolved_[i] == var) {

      unresolved_.Remove(i);

      return;

    }

  }

}

Variable* Scope::NewInternal(Handle<String> name) {

  ASSERT(!already_resolved());

  Variable* var = new(zone()) Variable(this,

                                       name,

                                       INTERNAL,

                                       false,

                                       Variable::NORMAL,

                                       kCreatedInitialized);

  internals_.Add(var, zone());

  return var;

}

Variable* Scope::NewTemporary(Handle<String> name) {

  ASSERT(!already_resolved());

  Variable* var = new(zone()) Variable(this,

                                       name,

                                       TEMPORARY,

                                       true,

                                       Variable::NORMAL,

                                       kCreatedInitialized);

  temps_.Add(var, zone());

  return var;

}

void Scope::AddDeclaration(Declaration* declaration) {

  decls_.Add(declaration, zone());

}

void Scope::SetIllegalRedeclaration(Expression* expression) {

  // Record only the first illegal redeclaration.

  if (!HasIllegalRedeclaration()) {

    illegal_redecl_ = expression;

  }

  ASSERT(HasIllegalRedeclaration());

}

void Scope::VisitIllegalRedeclaration(AstVisitor* visitor) {

  ASSERT(HasIllegalRedeclaration());

  illegal_redecl_->Accept(visitor);

}

Declaration* Scope::CheckConflictingVarDeclarations() {

  int length = decls_.length();

  for (int i = 0; i < length; i++) {

    Declaration* decl = decls_[i];

    if (decl->mode() != VAR) continue;

    Handle<String> name = decl->proxy()->name();

    // Iterate through all scopes until and including the declaration scope.

    Scope* previous = NULL;

    Scope* current = decl->scope();

    do {

      // There is a conflict if there exists a non-VAR binding.

      Variable* other_var = current->variables_.Lookup(name);

      if (other_var != NULL && other_var->mode() != VAR) {

        return decl;

      }

      previous = current;

      current = current->outer_scope_;

    } while (!previous->is_declaration_scope());

  }

  return NULL;

}

class VarAndOrder {

 public:

  VarAndOrder(Variable* var, int order) : var_(var), order_(order) { }

  Variable* var() const { return var_; }

  int order() const { return order_; }

  static int Compare(const VarAndOrder* a, const VarAndOrder* b) {

    return a->order_ - b->order_;

  }

 private:

  Variable* var_;

  int order_;

};

void Scope::CollectStackAndContextLocals(ZoneList<Variable*>* stack_locals,

                                         ZoneList<Variable*>* context_locals) {

  ASSERT(stack_locals != NULL);

  ASSERT(context_locals != NULL);

  // Collect internals which are always allocated on the heap.

  for (int i = 0; i < internals_.length(); i++) {

    Variable* var = internals_[i];

    if (var->is_used()) {

      ASSERT(var->IsContextSlot());

      context_locals->Add(var, zone());

    }

  }

  // Collect temporaries which are always allocated on the stack, unless the

  // context as a whole has forced context allocation.

  for (int i = 0; i < temps_.length(); i++) {

    Variable* var = temps_[i];

    if (var->is_used()) {

      if (var->IsContextSlot()) {

        ASSERT(has_forced_context_allocation());

        context_locals->Add(var, zone());

      } else {

        ASSERT(var->IsStackLocal());

        stack_locals->Add(var, zone());

      }

    }

  }

  // Collect declared local variables.

  ZoneList<VarAndOrder> vars(variables_.occupancy(), zone());

  for (VariableMap::Entry* p = variables_.Start();

       p != NULL;

       p = variables_.Next(p)) {

    Variable* var = reinterpret_cast<Variable*>(p->value);

    if (var->is_used()) {

      vars.Add(VarAndOrder(var, p->order), zone());

    }

  }

  vars.Sort(VarAndOrder::Compare);

  int var_count = vars.length();

  for (int i = 0; i < var_count; i++) {

    Variable* var = vars[i].var();

    if (var->IsStackLocal()) {

      stack_locals->Add(var, zone());

    } else if (var->IsContextSlot()) {

      context_locals->Add(var, zone());

    }

  }

}

bool Scope::AllocateVariables(CompilationInfo* info,

                              AstNodeFactory<AstNullVisitor>* factory) {

  // 1) Propagate scope information.

  bool outer_scope_calls_non_strict_eval = false;

  if (outer_scope_ != NULL) {

    outer_scope_calls_non_strict_eval =

        outer_scope_->outer_scope_calls_non_strict_eval() |

        outer_scope_->calls_non_strict_eval();

  }

  PropagateScopeInfo(outer_scope_calls_non_strict_eval);

  // 2) Allocate module instances.

  if (FLAG_harmony_modules && (is_global_scope() || is_module_scope())) {

    ASSERT(num_modules_ == 0);

    AllocateModulesRecursively(this);

  }

  // 3) Resolve variables.

  if (!ResolveVariablesRecursively(info, factory)) return false;

  // 4) Allocate variables.

  AllocateVariablesRecursively();

  return true;

}

bool Scope::HasTrivialContext() const {

  // A function scope has a trivial context if it always is the global

  // context. We iteratively scan out the context chain to see if

  // there is anything that makes this scope non-trivial; otherwise we

  // return true.

  for (const Scope* scope = this; scope != NULL; scope = scope->outer_scope_) {

    if (scope->is_eval_scope()) return false;

    if (scope->scope_inside_with_) return false;

    if (scope->num_heap_slots_ > 0) return false;

  }

  return true;

}

bool Scope::HasTrivialOuterContext() const {

  Scope* outer = outer_scope_;

  if (outer == NULL) return true;

  // Note that the outer context may be trivial in general, but the current

  // scope may be inside a 'with' statement in which case the outer context

  // for this scope is not trivial.

  return !scope_inside_with_ && outer->HasTrivialContext();

}

bool Scope::HasLazyCompilableOuterContext() const {

  Scope* outer = outer_scope_;

  if (outer == NULL) return true;

  // We have to prevent lazy compilation if this scope is inside a with scope

  // and all declaration scopes between them have empty contexts. Such

  // declaration scopes may become invisible during scope info deserialization.

  outer = outer->DeclarationScope();

  bool found_non_trivial_declarations = false;

  for (const Scope* scope = outer; scope != NULL; scope = scope->outer_scope_) {

    if (scope->is_with_scope() && !found_non_trivial_declarations) return false;

    if (scope->is_declaration_scope() && scope->num_heap_slots() > 0) {

      found_non_trivial_declarations = true;

    }

  }

  return true;

}

bool Scope::AllowsLazyCompilation() const {

  return !force_eager_compilation_ && HasLazyCompilableOuterContext();

}

bool Scope::AllowsLazyCompilationWithoutContext() const {

  return !force_eager_compilation_ && HasTrivialOuterContext();

}

int Scope::ContextChainLength(Scope* scope) {

  int n = 0;

  for (Scope* s = this; s != scope; s = s->outer_scope_) {

    ASSERT(s != NULL);  // scope must be in the scope chain

    if (s->is_with_scope() || s->num_heap_slots() > 0) n++;

    // Catch and module scopes always have heap slots.

    ASSERT(!s->is_catch_scope() || s->num_heap_slots() > 0);

    ASSERT(!s->is_module_scope() || s->num_heap_slots() > 0);

  }

  return n;

}

Scope* Scope::GlobalScope() {

  Scope* scope = this;

  while (!scope->is_global_scope()) {

    scope = scope->outer_scope();

  }

  return scope;

}

Scope* Scope::DeclarationScope() {

  Scope* scope = this;

  while (!scope->is_declaration_scope()) {

    scope = scope->outer_scope();

  }

  return scope;

}

Handle<ScopeInfo> Scope::GetScopeInfo() {

  if (scope_info_.is_null()) {

    scope_info_ = ScopeInfo::Create(this, zone());

  }

  return scope_info_;

}

void Scope::GetNestedScopeChain(

    List<Handle<ScopeInfo> >* chain,

    int position) {

  if (!is_eval_scope()) chain->Add(Handle<ScopeInfo>(GetScopeInfo()));

  for (int i = 0; i < inner_scopes_.length(); i++) {

    Scope* scope = inner_scopes_[i];

    int beg_pos = scope->start_position();

    int end_pos = scope->end_position();

    ASSERT(beg_pos >= 0 && end_pos >= 0);

    if (beg_pos <= position && position < end_pos) {

      scope->GetNestedScopeChain(chain, position);

      return;

    }

  }

}

#ifdef DEBUG

static const char* Header(ScopeType scope_type) {

  switch (scope_type) {

    case EVAL_SCOPE: return "eval";

    case FUNCTION_SCOPE: return "function";

    case MODULE_SCOPE: return "module";

    case GLOBAL_SCOPE: return "global";

    case CATCH_SCOPE: return "catch";

    case BLOCK_SCOPE: return "block";

    case WITH_SCOPE: return "with";

  }

  UNREACHABLE();

  return NULL;

}

static void Indent(int n, const char* str) {

  PrintF("%*s%s", n, "", str);

}

static void PrintName(Handle<String> name) {

  SmartArrayPointer<char> s = name->ToCString(DISALLOW_NULLS);

  PrintF("%s", *s);

}

static void PrintLocation(Variable* var) {

  switch (var->location()) {

    case Variable::UNALLOCATED:

      break;

    case Variable::PARAMETER:

      PrintF("parameter[%d]", var->index());

      break;

    case Variable::LOCAL:

      PrintF("local[%d]", var->index());

      break;

    case Variable::CONTEXT:

      PrintF("context[%d]", var->index());

      break;

    case Variable::LOOKUP:

      PrintF("lookup");

      break;

  }

}

static void PrintVar(int indent, Variable* var) {

  if (var->is_used() || !var->IsUnallocated()) {

    Indent(indent, Variable::Mode2String(var->mode()));

    PrintF(" ");

    PrintName(var->name());

    PrintF(";  // ");

    PrintLocation(var);

    if (var->has_forced_context_allocation()) {

      if (!var->IsUnallocated()) PrintF(", ");

      PrintF("forced context allocation");

    }

    PrintF("\n");

  }

}

static void PrintMap(int indent, VariableMap* map) {

  for (VariableMap::Entry* p = map->Start(); p != NULL; p = map->Next(p)) {

    Variable* var = reinterpret_cast<Variable*>(p->value);

    PrintVar(indent, var);

  }

}

void Scope::Print(int n) {

  int n0 = (n > 0 ? n : 0);

  int n1 = n0 + 2;  // indentation

  // Print header.

  Indent(n0, Header(scope_type_));

  if (scope_name_->length() > 0) {

    PrintF(" ");

    PrintName(scope_name_);

  }

  // Print parameters, if any.

  if (is_function_scope()) {

    PrintF(" (");

    for (int i = 0; i < params_.length(); i++) {

      if (i > 0) PrintF(", ");

      PrintName(params_[i]->name());

    }

    PrintF(")");

  }

  PrintF(" { // (%d, %d)\n", start_position(), end_position());

  // Function name, if any (named function literals, only).

  if (function_ != NULL) {

    Indent(n1, "// (local) function name: ");

    PrintName(function_->proxy()->name());

    PrintF("\n");

  }

  // Scope info.

  if (HasTrivialOuterContext()) {

    Indent(n1, "// scope has trivial outer context\n");

  }

  switch (language_mode()) {

    case CLASSIC_MODE:

      break;

    case STRICT_MODE:

      Indent(n1, "// strict mode scope\n");

      break;

    case EXTENDED_MODE:

      Indent(n1, "// extended mode scope\n");

      break;

  }

  if (scope_inside_with_) Indent(n1, "// scope inside 'with'\n");

  if (scope_contains_with_) Indent(n1, "// scope contains 'with'\n");

  if (scope_calls_eval_) Indent(n1, "// scope calls 'eval'\n");

  if (outer_scope_calls_non_strict_eval_) {

    Indent(n1, "// outer scope calls 'eval' in non-strict context\n");

  }

  if (inner_scope_calls_eval_) Indent(n1, "// inner scope calls 'eval'\n");

  if (num_stack_slots_ > 0) { Indent(n1, "// ");

  PrintF("%d stack slots\n", num_stack_slots_); }

  if (num_heap_slots_ > 0) { Indent(n1, "// ");

  PrintF("%d heap slots\n", num_heap_slots_); }

  // Print locals.

  if (function_ != NULL) {

    Indent(n1, "// function var:\n");

    PrintVar(n1, function_->proxy()->var());

  }

  if (temps_.length() > 0) {

    Indent(n1, "// temporary vars:\n");

    for (int i = 0; i < temps_.length(); i++) {

      PrintVar(n1, temps_[i]);

    }

  }

  if (internals_.length() > 0) {

    Indent(n1, "// internal vars:\n");

    for (int i = 0; i < internals_.length(); i++) {

      PrintVar(n1, internals_[i]);

    }

  }

  if (variables_.Start() != NULL) {

    Indent(n1, "// local vars:\n");

    PrintMap(n1, &variables_);

  }

  if (dynamics_ != NULL) {

    Indent(n1, "// dynamic vars:\n");

    PrintMap(n1, dynamics_->GetMap(DYNAMIC));

    PrintMap(n1, dynamics_->GetMap(DYNAMIC_LOCAL));

    PrintMap(n1, dynamics_->GetMap(DYNAMIC_GLOBAL));

  }

  // Print inner scopes (disable by providing negative n).

  if (n >= 0) {

    for (int i = 0; i < inner_scopes_.length(); i++) {

      PrintF("\n");

      inner_scopes_[i]->Print(n1);

    }

  }

  Indent(n0, "}\n");

}

#endif  // DEBUG

Variable* Scope::NonLocal(Handle<String> name, VariableMode mode) {

  if (dynamics_ == NULL) dynamics_ = new(zone()) DynamicScopePart(zone());

  VariableMap* map = dynamics_->GetMap(mode);

  Variable* var = map->Lookup(name);

  if (var == NULL) {

    // Declare a new non-local.

    InitializationFlag init_flag = (mode == VAR)

        ? kCreatedInitialized : kNeedsInitialization;

    var = map->Declare(NULL,

                       name,

                       mode,

                       true,

                       Variable::NORMAL,

                       init_flag);

    // Allocate it by giving it a dynamic lookup.

    var->AllocateTo(Variable::LOOKUP, -1);

  }

  return var;

}

Variable* Scope::LookupRecursive(Handle<String> name,

                                 BindingKind* binding_kind,

                                 AstNodeFactory<AstNullVisitor>* factory) {

  ASSERT(binding_kind != NULL);

  if (already_resolved() && is_with_scope()) {

    // Short-cut: if the scope is deserialized from a scope info, variable

    // allocation is already fixed.  We can simply return with dynamic lookup.

    *binding_kind = DYNAMIC_LOOKUP;

    return NULL;

  }

  // Try to find the variable in this scope.

  Variable* var = LocalLookup(name);

  // We found a variable and we are done. (Even if there is an 'eval' in

  // this scope which introduces the same variable again, the resulting

  // variable remains the same.)

  if (var != NULL) {

    *binding_kind = BOUND;

    return var;

  }

  // We did not find a variable locally. Check against the function variable,

  // if any. We can do this for all scopes, since the function variable is

  // only present - if at all - for function scopes.

  *binding_kind = UNBOUND;

  var = LookupFunctionVar(name, factory);

  if (var != NULL) {

    *binding_kind = BOUND;

  } else if (outer_scope_ != NULL) {

    var = outer_scope_->LookupRecursive(name, binding_kind, factory);

    if (*binding_kind == BOUND && (is_function_scope() || is_with_scope())) {

      var->ForceContextAllocation();

    }

  } else {

    ASSERT(is_global_scope());

  }

  if (is_with_scope()) {

    ASSERT(!already_resolved());

    // The current scope is a with scope, so the variable binding can not be

    // statically resolved. However, note that it was necessary to do a lookup

    // in the outer scope anyway, because if a binding exists in an outer scope,

    // the associated variable has to be marked as potentially being accessed

    // from inside of an inner with scope (the property may not be in the 'with'

    // object).

    *binding_kind = DYNAMIC_LOOKUP;

    return NULL;

  } else if (calls_non_strict_eval()) {

    // A variable binding may have been found in an outer scope, but the current

    // scope makes a non-strict 'eval' call, so the found variable may not be

    // the correct one (the 'eval' may introduce a binding with the same name).

    // In that case, change the lookup result to reflect this situation.

    if (*binding_kind == BOUND) {

      *binding_kind = BOUND_EVAL_SHADOWED;

    } else if (*binding_kind == UNBOUND) {

      *binding_kind = UNBOUND_EVAL_SHADOWED;

    }

  }

  return var;

}

bool Scope::ResolveVariable(CompilationInfo* info,

                            VariableProxy* proxy,

                            AstNodeFactory<AstNullVisitor>* factory) {

  ASSERT(info->global_scope()->is_global_scope());

  // If the proxy is already resolved there's nothing to do

  // (functions and consts may be resolved by the parser).

  if (proxy->var() != NULL) return true;

  // Otherwise, try to resolve the variable.

  BindingKind binding_kind;

  Variable* var = LookupRecursive(proxy->name(), &binding_kind, factory);

  switch (binding_kind) {

    case BOUND:

      // We found a variable binding.

      break;

    case BOUND_EVAL_SHADOWED:

      // We either found a variable binding that might be shadowed by eval  or

      // gave up on it (e.g. by encountering a local with the same in the outer

      // scope which was not promoted to a context, this can happen if we use

      // debugger to evaluate arbitrary expressions at a break point).

      if (var->IsGlobalObjectProperty()) {

        var = NonLocal(proxy->name(), DYNAMIC_GLOBAL);

      } else if (var->is_dynamic()) {

        var = NonLocal(proxy->name(), DYNAMIC);

      } else {

        Variable* invalidated = var;

        var = NonLocal(proxy->name(), DYNAMIC_LOCAL);

        var->set_local_if_not_shadowed(invalidated);

      }

      break;

    case UNBOUND:

      // No binding has been found. Declare a variable on the global object.

      var = info->global_scope()->DeclareDynamicGlobal(proxy->name());

      break;

    case UNBOUND_EVAL_SHADOWED:

      // No binding has been found. But some scope makes a

      // non-strict 'eval' call.

      var = NonLocal(proxy->name(), DYNAMIC_GLOBAL);

      break;

    case DYNAMIC_LOOKUP:

      // The variable could not be resolved statically.

      var = NonLocal(proxy->name(), DYNAMIC);

      break;

  }

  ASSERT(var != NULL);

  if (FLAG_harmony_scoping && is_extended_mode() &&

      var->is_const_mode() && proxy->IsLValue()) {

    // Assignment to const. Throw a syntax error.

    MessageLocation location(

        info->script(), proxy->position(), proxy->position());

    Isolate* isolate = info->isolate();

    Factory* factory = isolate->factory();

    Handle<JSArray> array = factory->NewJSArray(0);

    Handle<Object> result =

        factory->NewSyntaxError("harmony_const_assign", array);

    isolate->Throw(*result, &location);

    return false;

  }

  if (FLAG_harmony_modules) {

    bool ok;

#ifdef DEBUG

    if (FLAG_print_interface_details)

      PrintF("# Resolve %s:\n", var->name()->ToAsciiArray());

#endif

    proxy->interface()->Unify(var->interface(), zone(), &ok);

    if (!ok) {

#ifdef DEBUG

      if (FLAG_print_interfaces) {

        PrintF("SCOPES TYPE ERROR\n");

        PrintF("proxy: ");

        proxy->interface()->Print();

        PrintF("var: ");

        var->interface()->Print();

      }

#endif

      // Inconsistent use of module. Throw a syntax error.

      // TODO(rossberg): generate more helpful error message.

      MessageLocation location(

          info->script(), proxy->position(), proxy->position());

      Isolate* isolate = info->isolate();

      Factory* factory = isolate->factory();

      Handle<JSArray> array = factory->NewJSArray(1);

      USE(JSObject::SetElement(array, 0, var->name(), NONE, kStrictMode));

      Handle<Object> result =

          factory->NewSyntaxError("module_type_error", array);

      isolate->Throw(*result, &location);

      return false;

    }

  }

  proxy->BindTo(var);

  return true;

}

bool Scope::ResolveVariablesRecursively(

    CompilationInfo* info,

    AstNodeFactory<AstNullVisitor>* factory) {

  ASSERT(info->global_scope()->is_global_scope());

  // Resolve unresolved variables for this scope.

  for (int i = 0; i < unresolved_.length(); i++) {

    if (!ResolveVariable(info, unresolved_[i], factory)) return false;

  }

  // Resolve unresolved variables for inner scopes.

  for (int i = 0; i < inner_scopes_.length(); i++) {

    if (!inner_scopes_[i]->ResolveVariablesRecursively(info, factory))

      return false;

  }

  return true;

}

bool Scope::PropagateScopeInfo(bool outer_scope_calls_non_strict_eval ) {

  if (outer_scope_calls_non_strict_eval) {

    outer_scope_calls_non_strict_eval_ = true;

  }

  bool calls_non_strict_eval =

      this->calls_non_strict_eval() || outer_scope_calls_non_strict_eval_;

  for (int i = 0; i < inner_scopes_.length(); i++) {

    Scope* inner_scope = inner_scopes_[i];

    if (inner_scope->PropagateScopeInfo(calls_non_strict_eval)) {

      inner_scope_calls_eval_ = true;

    }

    if (inner_scope->force_eager_compilation_) {

      force_eager_compilation_ = true;

    }

  }

  return scope_calls_eval_ || inner_scope_calls_eval_;

}

bool Scope::MustAllocate(Variable* var) {

  // Give var a read/write use if there is a chance it might be accessed

  // via an eval() call.  This is only possible if the variable has a

  // visible name.

  if ((var->is_this() || var->name()->length() > 0) &&

      (var->has_forced_context_allocation() ||

       scope_calls_eval_ ||

       inner_scope_calls_eval_ ||

       scope_contains_with_ ||

       is_catch_scope() ||

       is_block_scope() ||

       is_module_scope() ||

       is_global_scope())) {

    var->set_is_used(true);

  }

  // Global variables do not need to be allocated.

  return !var->IsGlobalObjectProperty() && var->is_used();

}

bool Scope::MustAllocateInContext(Variable* var) {

  // If var is accessed from an inner scope, or if there is a possibility

  // that it might be accessed from the current or an inner scope (through

  // an eval() call or a runtime with lookup), it must be allocated in the

  // context.

  //

  // Exceptions: If the scope as a whole has forced context allocation, all

  // variables will have context allocation, even temporaries.  Otherwise

  // temporary variables are always stack-allocated.  Catch-bound variables are

  // always context-allocated.

  if (has_forced_context_allocation()) return true;

  if (var->mode() == TEMPORARY) return false;

  if (var->mode() == INTERNAL) return true;

  if (is_catch_scope() || is_block_scope() || is_module_scope()) return true;

  if (is_global_scope() && IsLexicalVariableMode(var->mode())) return true;

  return var->has_forced_context_allocation() ||

      scope_calls_eval_ ||

      inner_scope_calls_eval_ ||

      scope_contains_with_;

}

bool Scope::HasArgumentsParameter() {

  for (int i = 0; i < params_.length(); i++) {

    if (params_[i]->name().is_identical_to(

            isolate_->factory()->arguments_string())) {

      return true;

    }

  }

  return false;

}

void Scope::AllocateStackSlot(Variable* var) {

  var->AllocateTo(Variable::LOCAL, num_stack_slots_++);

}

void Scope::AllocateHeapSlot(Variable* var) {

  var->AllocateTo(Variable::CONTEXT, num_heap_slots_++);

}

void Scope::AllocateParameterLocals() {

  ASSERT(is_function_scope());

  Variable* arguments = LocalLookup(isolate_->factory()->arguments_string());

  ASSERT(arguments != NULL);  // functions have 'arguments' declared implicitly

  bool uses_nonstrict_arguments = false;

  if (MustAllocate(arguments) && !HasArgumentsParameter()) {

    // 'arguments' is used. Unless there is also a parameter called

    // 'arguments', we must be conservative and allocate all parameters to

    // the context assuming they will be captured by the arguments object.

    // If we have a parameter named 'arguments', a (new) value is always

    // assigned to it via the function invocation. Then 'arguments' denotes

    // that specific parameter value and cannot be used to access the

    // parameters, which is why we don't need to allocate an arguments

    // object in that case.

    // We are using 'arguments'. Tell the code generator that is needs to

    // allocate the arguments object by setting 'arguments_'.

    arguments_ = arguments;

    // In strict mode 'arguments' does not alias formal parameters.

    // Therefore in strict mode we allocate parameters as if 'arguments'

    // were not used.

    uses_nonstrict_arguments = is_classic_mode();

  }

  // The same parameter may occur multiple times in the parameters_ list.

  // If it does, and if it is not copied into the context object, it must

  // receive the highest parameter index for that parameter; thus iteration

  // order is relevant!

  for (int i = params_.length() - 1; i >= 0; --i) {

    Variable* var = params_[i];

    ASSERT(var->scope() == this);

    if (uses_nonstrict_arguments) {

      // Force context allocation of the parameter.

      var->ForceContextAllocation();

    }

    if (MustAllocate(var)) {

      if (MustAllocateInContext(var)) {

        ASSERT(var->IsUnallocated() || var->IsContextSlot());

        if (var->IsUnallocated()) {

          AllocateHeapSlot(var);

        }

      } else {

        ASSERT(var->IsUnallocated() || var->IsParameter());

        if (var->IsUnallocated()) {

          var->AllocateTo(Variable::PARAMETER, i);

        }

      }

    }

  }

}

void Scope::AllocateNonParameterLocal(Variable* var) {

  ASSERT(var->scope() == this);

  ASSERT(!var->IsVariable(isolate_->factory()->result_string()) ||

         !var->IsStackLocal());

  if (var->IsUnallocated() && MustAllocate(var)) {

    if (MustAllocateInContext(var)) {

      AllocateHeapSlot(var);

    } else {

      AllocateStackSlot(var);

    }

  }

}

void Scope::AllocateNonParameterLocals() {

  // All variables that have no rewrite yet are non-parameter locals.

  for (int i = 0; i < temps_.length(); i++) {

    AllocateNonParameterLocal(temps_[i]);

  }

  for (int i = 0; i < internals_.length(); i++) {

    AllocateNonParameterLocal(internals_[i]);

  }

  ZoneList<VarAndOrder> vars(variables_.occupancy(), zone());

  for (VariableMap::Entry* p = variables_.Start();

       p != NULL;

       p = variables_.Next(p)) {

    Variable* var = reinterpret_cast<Variable*>(p->value);

    vars.Add(VarAndOrder(var, p->order), zone());

  }

  vars.Sort(VarAndOrder::Compare);

  int var_count = vars.length();

  for (int i = 0; i < var_count; i++) {

    AllocateNonParameterLocal(vars[i].var());

  }

  // For now, function_ must be allocated at the very end.  If it gets

  // allocated in the context, it must be the last slot in the context,

  // because of the current ScopeInfo implementation (see

  // ScopeInfo::ScopeInfo(FunctionScope* scope) constructor).

  if (function_ != NULL) {

    AllocateNonParameterLocal(function_->proxy()->var());

  }

}

void Scope::AllocateVariablesRecursively() {

  // Allocate variables for inner scopes.

  for (int i = 0; i < inner_scopes_.length(); i++) {

    inner_scopes_[i]->AllocateVariablesRecursively();

  }

  // If scope is already resolved, we still need to allocate

  // variables in inner scopes which might not had been resolved yet.

  if (already_resolved()) return;

  // The number of slots required for variables.

  num_stack_slots_ = 0;

  num_heap_slots_ = Context::MIN_CONTEXT_SLOTS;

  // Allocate variables for this scope.

  // Parameters must be allocated first, if any.

  if (is_function_scope()) AllocateParameterLocals();

  AllocateNonParameterLocals();