Preparse top-level functions in discardable zones

src/parsing/parser.cc

Index: src/parsing/parser.cc
diff --git a/src/parsing/parser.cc b/src/parsing/parser.cc
index cd87da8d14bfb46babba23408e08a987b795a9ca..0ada440354515d4fd7f6e73437d2359912da9b5d 100644
--- a/src/parsing/parser.cc
+++ b/src/parsing/parser.cc
@@ -127,13 +127,15 @@ class DiscardableZoneScope {
       }
     }
   }
-  ~DiscardableZoneScope() {
+  void Reset() {
     parser_->fni_ = prev_fni_;
     parser_->zone_ = prev_zone_;
     if (parser_->reusable_preparser_ != nullptr) {
       parser_->reusable_preparser_->zone_ = prev_zone_;
     }
+    ast_node_factory_scope_.Reset();
   }
+  ~DiscardableZoneScope() { Reset(); }
 
  private:
   AstNodeFactory::BodyScope ast_node_factory_scope_;
@@ -2680,11 +2682,11 @@ FunctionLiteral* Parser::ParseFunctionLiteral(
   // will migrate unresolved variable into a Scope in the main Zone.
   // TODO(marja): Refactor parsing modes: simplify this.
   bool use_temp_zone =
-      !is_lazy_top_level_function && allow_lazy() &&
-      function_type == FunctionLiteral::kDeclaration &&
+      allow_lazy() && function_type == FunctionLiteral::kDeclaration &&
       eager_compile_hint != FunctionLiteral::kShouldEagerCompile &&
       !(FLAG_validate_asm && scope()->IsAsmModule());
-  bool is_lazy_inner_function = use_temp_zone && FLAG_lazy_inner_functions;
+  bool is_lazy_inner_function =
+      use_temp_zone && FLAG_lazy_inner_functions && !is_lazy_top_level_function;
 
   // This Scope lives in the main zone. We'll migrate data into that zone later.
   DeclarationScope* scope = NewFunctionScope(kind);
@@ -2698,6 +2700,45 @@ FunctionLiteral* Parser::ParseFunctionLiteral(
   bool should_be_used_once_hint = false;
   bool has_duplicate_parameters;
 
+  FunctionState function_state(&function_state_, &scope_state_, scope);
+#ifdef DEBUG
+  scope->SetScopeName(function_name);
+#endif
+
+  ExpressionClassifier formals_classifier(this, &duplicate_finder);
+
+  if (is_generator) {
+    // For generators, allocating variables in contexts is currently a win
+    // because it minimizes the work needed to suspend and resume an
+    // activation.  The machine code produced for generators (by full-codegen)
+    // relies on this forced context allocation, but not in an essential way.
+    this->scope()->ForceContextAllocation();
+
+    // Calling a generator returns a generator object.  That object is stored
+    // in a temporary variable, a definition that is used by "yield"
+    // expressions. This also marks the FunctionState as a generator.
+    Variable* temp =
+        NewTemporary(ast_value_factory()->dot_generator_object_string());
+    function_state.set_generator_object_variable(temp);
+  }
+
+  Expect(Token::LPAREN, CHECK_OK);
+  int start_position = scanner()->location().beg_pos;
+  this->scope()->set_start_position(start_position);
+  ParserFormalParameters formals(scope);
+  ParseFormalParameterList(&formals, CHECK_OK);
+  arity = formals.Arity();
+  Expect(Token::RPAREN, CHECK_OK);
+  int formals_end_position = scanner()->location().end_pos;
+
+  CheckArityRestrictions(arity, kind, formals.has_rest, start_position,
+                         formals_end_position, CHECK_OK);
+  Expect(Token::LBRACE, CHECK_OK);
+  // Don't include the rest parameter into the function's formal parameter
+  // count (esp. the SharedFunctionInfo::internal_formal_parameter_count,
+  // which says whether we need to create an arguments adaptor frame).
+  if (formals.has_rest) arity--;
+
   {
     // Temporary zones can nest. When we migrate free variables (see below), we
     // need to recreate them in the previous Zone.
@@ -2711,45 +2752,9 @@ FunctionLiteral* Parser::ParseFunctionLiteral(
     // information when the function is parsed.
     Zone temp_zone(zone()->allocator());
     DiscardableZoneScope zone_scope(this, &temp_zone, use_temp_zone);
-
-    FunctionState function_state(&function_state_, &scope_state_, scope);
 #ifdef DEBUG
-    scope->SetScopeName(function_name);
     if (use_temp_zone) scope->set_needs_migration();
 #endif
-    ExpressionClassifier formals_classifier(this, &duplicate_finder);
-
-    if (is_generator) {
-      // For generators, allocating variables in contexts is currently a win
-      // because it minimizes the work needed to suspend and resume an
-      // activation.  The machine code produced for generators (by full-codegen)
-      // relies on this forced context allocation, but not in an essential way.
-      this->scope()->ForceContextAllocation();
-
-      // Calling a generator returns a generator object.  That object is stored
-      // in a temporary variable, a definition that is used by "yield"
-      // expressions. This also marks the FunctionState as a generator.
-      Variable* temp =
-          NewTemporary(ast_value_factory()->dot_generator_object_string());
-      function_state.set_generator_object_variable(temp);
-    }
-
-    Expect(Token::LPAREN, CHECK_OK);
-    int start_position = scanner()->location().beg_pos;
-    this->scope()->set_start_position(start_position);
-    ParserFormalParameters formals(scope);
-    ParseFormalParameterList(&formals, CHECK_OK);
-    arity = formals.Arity();
-    Expect(Token::RPAREN, CHECK_OK);
-    int formals_end_position = scanner()->location().end_pos;
-
-    CheckArityRestrictions(arity, kind, formals.has_rest, start_position,
-                           formals_end_position, CHECK_OK);
-    Expect(Token::LBRACE, CHECK_OK);
-    // Don't include the rest parameter into the function's formal parameter
-    // count (esp. the SharedFunctionInfo::internal_formal_parameter_count,
-    // which says whether we need to create an arguments adaptor frame).
-    if (formals.has_rest) arity--;
 
     // Eager or lazy parse? If is_lazy_top_level_function, we'll parse
     // lazily. We'll call SkipLazyFunctionBody, which may decide to abort lazy
@@ -2778,6 +2783,8 @@ FunctionLiteral* Parser::ParseFunctionLiteral(
         eager_compile_hint = FunctionLiteral::kShouldEagerCompile;
         should_be_used_once_hint = true;
         scope->ResetAfterPreparsing(true);
+        zone_scope.Reset();
+        use_temp_zone = false;
       }
     }