Don't use different function scopes when parsing with temp zones

src/ast/scopes.cc

 // Copyright 2012 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/ast/scopes.h"
 
 #include <set>
 
 #include "src/accessors.h"
 #include "src/ast/ast.h"
@@ skipping 97 matching lines @@
       variables_(zone),
       locals_(4, zone),
       decls_(4, zone),
       scope_type_(scope_type) {
   DCHECK_NE(SCRIPT_SCOPE, scope_type);
   SetDefaults();
   set_language_mode(outer_scope->language_mode());
   force_context_allocation_ =
       !is_function_scope() && outer_scope->has_forced_context_allocation();
   outer_scope_->AddInnerScope(this);
-  if (outer_scope_->is_lazily_parsed_) is_lazily_parsed_ = true;
 }
 
 Scope::Snapshot::Snapshot(Scope* scope)
     : outer_scope_(scope),
       top_inner_scope_(scope->inner_scope_),
       top_unresolved_(scope->unresolved_),
       top_local_(scope->GetClosureScope()->locals_.length()),
       top_decl_(scope->GetClosureScope()->decls_.length()) {}
 
 DeclarationScope::DeclarationScope(Zone* zone,
@@ skipping 142 matching lines @@
   function_ = nullptr;
   arguments_ = nullptr;
   this_function_ = nullptr;
   arity_ = 0;
 }
 
 void Scope::SetDefaults() {
 #ifdef DEBUG
   scope_name_ = nullptr;
   already_resolved_ = false;
+  needs_migration_ = false;
 #endif
   inner_scope_ = nullptr;
   sibling_ = nullptr;
   unresolved_ = nullptr;
 
   start_position_ = kNoSourcePosition;
   end_position_ = kNoSourcePosition;
 
   num_stack_slots_ = 0;
   num_heap_slots_ = Context::MIN_CONTEXT_SLOTS;
@@ skipping 655 matching lines @@
 }
 
 VariableProxy* Scope::NewUnresolved(AstNodeFactory* factory,
                                     const AstRawString* name,
                                     int start_position, int end_position,
                                     VariableKind kind) {
   // Note that we must not share the unresolved variables with
   // the same name because they may be removed selectively via
   // RemoveUnresolved().
   DCHECK(!already_resolved_);
-  DCHECK_EQ(factory->zone(), zone());
+  DCHECK(needs_migration_ || factory->zone() == zone());
   VariableProxy* proxy =
       factory->NewVariableProxy(name, kind, start_position, end_position);
   proxy->set_next_unresolved(unresolved_);
   unresolved_ = proxy;
   return proxy;
 }
 
 void Scope::AddUnresolved(VariableProxy* proxy) {
   DCHECK(!already_resolved_);
   DCHECK(!proxy->is_resolved());
@@ skipping 238 matching lines @@
       Variable* var = params_[i];
       if (var->mode() == TEMPORARY) {
         locals_.Add(var, zone());
       } else if (variables_.Lookup(var->raw_name()) == nullptr) {
         variables_.Add(zone(), var);
         locals_.Add(var, zone());
       }
     }
   } else {
     params_.Clear();
-    // Make sure we won't try to allocate the rest parameter. {params_} was
-    // cleared above.
-    has_rest_ = false;

[adamk, 2016/09/27 20:33:17]

Was this just unnecessary?

[Toon Verwaest, 2016/09/27 20:41:44]

It was necessary to make allocation of these scopes work; but now we explicitly
never allocate them to reduce risk of accidental breakage later. Otherwise we'd
have to keep all special variables synced here like new_target_ etc.

   }
+
+#ifdef DEBUG
+  needs_migration_ = false;
+#endif
+
+  is_lazily_parsed_ = !aborted;
 }
 
-void DeclarationScope::AnalyzePartially(DeclarationScope* migrate_to,
-                                        AstNodeFactory* ast_node_factory) {
-  // Try to resolve unresolved variables for this Scope and migrate those which
-  // cannot be resolved inside. It doesn't make sense to try to resolve them in
-  // the outer Scopes here, because they are incomplete.
-  for (VariableProxy* proxy =
-           FetchFreeVariables(this, !FLAG_lazy_inner_functions);
-       proxy != nullptr; proxy = proxy->next_unresolved()) {
-    DCHECK(!proxy->is_resolved());
-    VariableProxy* copy = ast_node_factory->CopyVariableProxy(proxy);
-    migrate_to->AddUnresolved(copy);
+void DeclarationScope::AnalyzePartially(AstNodeFactory* ast_node_factory) {
+  DCHECK(!force_eager_compilation_);
+  VariableProxy* unresolved = nullptr;
+
+  if (!outer_scope_->is_script_scope()) {
+    // Try to resolve unresolved variables for this Scope and migrate those
+    // which cannot be resolved inside. It doesn't make sense to try to resolve
+    // them in the outer Scopes here, because they are incomplete.
+    for (VariableProxy* proxy =
+             FetchFreeVariables(this, !FLAG_lazy_inner_functions);
+         proxy != nullptr; proxy = proxy->next_unresolved()) {
+      DCHECK(!proxy->is_resolved());
+      VariableProxy* copy = ast_node_factory->CopyVariableProxy(proxy);
+      copy->set_next_unresolved(unresolved);
+      unresolved = copy;
+    }
   }
 
-  // Push scope data up to migrate_to. Note that migrate_to and this Scope
-  // describe the same Scope, just in different Zones.
-  PropagateUsageFlagsToScope(migrate_to);
-  if (scope_uses_super_property_) migrate_to->scope_uses_super_property_ = true;
-  if (inner_scope_calls_eval_) migrate_to->inner_scope_calls_eval_ = true;
-  if (is_lazily_parsed_) migrate_to->is_lazily_parsed_ = true;
-  DCHECK(!force_eager_compilation_);
-  migrate_to->set_start_position(start_position_);
-  migrate_to->set_end_position(end_position_);
-  migrate_to->set_language_mode(language_mode());
-  migrate_to->arity_ = arity_;
-  migrate_to->force_context_allocation_ = force_context_allocation_;
-  outer_scope_->RemoveInnerScope(this);
-  DCHECK_EQ(outer_scope_, migrate_to->outer_scope_);
-  DCHECK_EQ(outer_scope_->zone(), migrate_to->zone());
-  DCHECK_EQ(NeedsHomeObject(), migrate_to->NeedsHomeObject());
-  DCHECK_EQ(asm_function_, migrate_to->asm_function_);
+  ResetAfterPreparsing(false);
+
+  unresolved_ = unresolved;
 }
 
 #ifdef DEBUG
 static const char* Header(ScopeType scope_type, FunctionKind function_kind,
                           bool is_declaration_scope) {
   switch (scope_type) {
     case EVAL_SCOPE: return "eval";
     // TODO(adamk): Should we print concise method scopes specially?
     case FUNCTION_SCOPE:
       if (IsGeneratorFunction(function_kind)) return "function*";
@@ skipping 178 matching lines @@
   if (!is_hidden() && inner_scope_ == nullptr) {
     CHECK_NE(kNoSourcePosition, start_position());
     CHECK_NE(kNoSourcePosition, end_position());
   }
   for (Scope* scope = inner_scope_; scope != nullptr; scope = scope->sibling_) {
     scope->CheckScopePositions();
   }
 }
 
 void Scope::CheckZones() {
+  DCHECK(!needs_migration_);
   for (Scope* scope = inner_scope_; scope != nullptr; scope = scope->sibling_) {
     CHECK_EQ(scope->zone(), zone());
   }
 }
 #endif  // DEBUG
 
 Variable* Scope::NonLocal(const AstRawString* name, VariableMode mode) {
   // Declare a new non-local.
   DCHECK(IsDynamicVariableMode(mode));
   Variable* var = variables_.Declare(zone(), NULL, name, mode, NORMAL_VARIABLE,
@@ skipping 351 matching lines @@
 
   for (const auto& it : module()->regular_exports()) {
     Variable* var = LookupLocal(it.first);
     var->AllocateTo(VariableLocation::MODULE, 0);
   }
 }
 
 void Scope::AllocateVariablesRecursively() {
   DCHECK(!already_resolved_);
   DCHECK_EQ(0, num_stack_slots_);
+  // Don't allocate variables of preparsed scopes.
+  if (is_lazily_parsed_) return;
 
   // Allocate variables for inner scopes.
   for (Scope* scope = inner_scope_; scope != nullptr; scope = scope->sibling_) {
     scope->AllocateVariablesRecursively();
   }
 
   DCHECK(!already_resolved_);
   DCHECK_EQ(Context::MIN_CONTEXT_SLOTS, num_heap_slots_);
 
   // Allocate variables for this scope.
@@ skipping 58 matching lines @@
   Variable* function =
       is_function_scope() ? AsDeclarationScope()->function_var() : nullptr;
   bool is_function_var_in_context =
       function != nullptr && function->IsContextSlot();
   return num_heap_slots() - Context::MIN_CONTEXT_SLOTS -
          (is_function_var_in_context ? 1 : 0);
 }
 
 }  // namespace internal
 }  // namespace v8