Put Scopes into temporary Zone (second try)

src/parsing/parser.cc

Index: src/parsing/parser.cc
diff --git a/src/parsing/parser.cc b/src/parsing/parser.cc
index f49fd1f95f1845661d76c41c68e28238d14ad653..c3338dc599034114b33be6ffdc3e528b15f9fd6f 100644
--- a/src/parsing/parser.cc
+++ b/src/parsing/parser.cc
@@ -204,18 +204,26 @@ class DiscardableZoneScope {
       : ast_node_factory_scope_(parser->factory(), temp_zone, use_temp_zone),
         fni_(parser->ast_value_factory_, temp_zone),
         parser_(parser),
-        prev_fni_(parser->fni_) {
+        prev_fni_(parser->fni_),
+        prev_zone_(parser->zone_) {
     if (use_temp_zone) {
       parser_->fni_ = &fni_;
+      parser_->zone_ = temp_zone;
     }
   }
-  ~DiscardableZoneScope() { parser_->fni_ = prev_fni_; }
+  ~DiscardableZoneScope() {
+    parser_->fni_ = prev_fni_;
+    parser_->zone_ = prev_zone_;
+  }
 
  private:
   AstNodeFactory::BodyScope ast_node_factory_scope_;
   FuncNameInferrer fni_;
   Parser* parser_;
   FuncNameInferrer* prev_fni_;
+  Zone* prev_zone_;
+
+  DISALLOW_COPY_AND_ASSIGN(DiscardableZoneScope);
 };
 
 void Parser::SetCachedData(ParseInfo* info) {
@@ -4313,29 +4321,113 @@ FunctionLiteral* Parser::ParseFunctionLiteral(
     function_name = ast_value_factory()->empty_string();
   }
 
-  Scope* scope = NewFunctionScope(kind);
-  SetLanguageMode(scope, language_mode);
-  ZoneList<Statement*>* body = NULL;
+  FunctionLiteral::EagerCompileHint eager_compile_hint =
+      function_state_->next_function_is_parenthesized()
+          ? FunctionLiteral::kShouldEagerCompile
+          : FunctionLiteral::kShouldLazyCompile;
+
+  // Determine if the function can be parsed lazily. Lazy parsing is
+  // different from lazy compilation; we need to parse more eagerly than we
+  // compile.
+
+  // We can only parse lazily if we also compile lazily. The heuristics for lazy
+  // compilation are:
+  // - It must not have been prohibited by the caller to Parse (some callers
+  //   need a full AST).
+  // - The outer scope must allow lazy compilation of inner functions.
+  // - The function mustn't be a function expression with an open parenthesis
+  //   before; we consider that a hint that the function will be called
+  //   immediately, and it would be a waste of time to make it lazily
+  //   compiled.
+  // These are all things we can know at this point, without looking at the
+  // function itself.
+
+  // In addition, we need to distinguish between these cases:
+  // (function foo() {
+  //   bar = function() { return 1; }
+  //  })();
+  // and
+  // (function foo() {
+  //   var a = 1;
+  //   bar = function() { return a; }
+  //  })();
+
+  // Now foo will be parsed eagerly and compiled eagerly (optimization: assume
+  // parenthesis before the function means that it will be called
+  // immediately). The inner function *must* be parsed eagerly to resolve the
+  // possible reference to the variable in foo's scope. However, it's possible
+  // that it will be compiled lazily.
+
+  // To make this additional case work, both Parser and PreParser implement a
+  // logic where only top-level functions will be parsed lazily.
+  bool is_lazily_parsed = mode() == PARSE_LAZILY &&
+                          this->scope()->AllowsLazyParsing() &&
+                          !function_state_->next_function_is_parenthesized();
+
+  // Determine whether the function body can be discarded after parsing.
+  // The preconditions are:
+  // - Lazy compilation has to be enabled.
+  // - Neither V8 natives nor native function declarations can be allowed,
+  //   since parsing one would retroactively force the function to be
+  //   eagerly compiled.
+  // - The invoker of this parser can't depend on the AST being eagerly
+  //   built (either because the function is about to be compiled, or
+  //   because the AST is going to be inspected for some reason).
+  // - Because of the above, we can't be attempting to parse a
+  //   FunctionExpression; even without enclosing parentheses it might be
+  //   immediately invoked.
+  // - The function literal shouldn't be hinted to eagerly compile.
+  // - For asm.js functions the body needs to be available when module
+  //   validation is active, because we examine the entire module at once.
+  bool use_temp_zone =
+      !is_lazily_parsed && FLAG_lazy && !allow_natives() &&
+      extension_ == NULL && allow_lazy() &&
+      function_type == FunctionLiteral::kDeclaration &&
+      eager_compile_hint != FunctionLiteral::kShouldEagerCompile &&
+      !(FLAG_validate_asm && scope()->asm_module());
+
+  Scope* main_scope = nullptr;
+  if (use_temp_zone) {
+    // This Scope lives in the main Zone; we'll migrate data into it later.
+    main_scope = NewFunctionScope(kind);
+  }
+
+  ZoneList<Statement*>* body = nullptr;
   int arity = -1;
   int materialized_literal_count = -1;
   int expected_property_count = -1;
   DuplicateFinder duplicate_finder(scanner()->unicode_cache());
   bool should_be_used_once_hint = false;
   bool has_duplicate_parameters;
-  FunctionLiteral::EagerCompileHint eager_compile_hint;
 
-  // Parse function.
   {
+    // Temporary zones can nest. When we migrate free variables (see below), we
+    // need to recreate them in the previous Zone.
+    AstNodeFactory previous_zone_ast_node_factory(ast_value_factory());
+    previous_zone_ast_node_factory.set_zone(zone());
+
+    // Open a new zone scope, which sets our AstNodeFactory to allocate in the
+    // new temporary zone if the preconditions are satisfied, and ensures that
+    // the previous zone is always restored after parsing the body. To be able
+    // to do scope analysis correctly after full parsing, we migrate needed
+    // information from scope into main_scope when the function has been parsed.
+    Zone temp_zone(zone()->allocator());
+    DiscardableZoneScope zone_scope(this, &temp_zone, use_temp_zone);
+
+    Scope* scope = NewFunctionScope(kind);
+    SetLanguageMode(scope, language_mode);
+    if (!use_temp_zone) {
+      main_scope = scope;
+    } else {
+      DCHECK(main_scope->zone() != scope->zone());
+    }
+
     FunctionState function_state(&function_state_, &scope_state_, scope, kind);
 #ifdef DEBUG
     this->scope()->SetScopeName(function_name);
 #endif
     ExpressionClassifier formals_classifier(this, &duplicate_finder);
 
-    eager_compile_hint = function_state_->this_function_is_parenthesized()
-                             ? FunctionLiteral::kShouldEagerCompile
-                             : FunctionLiteral::kShouldLazyCompile;
-
     if (is_generator) {
       // For generators, allocating variables in contexts is currently a win
       // because it minimizes the work needed to suspend and resume an
@@ -4368,43 +4460,6 @@ FunctionLiteral* Parser::ParseFunctionLiteral(
     // which says whether we need to create an arguments adaptor frame).
     if (formals.has_rest) arity--;
 
-    // Determine if the function can be parsed lazily. Lazy parsing is different
-    // from lazy compilation; we need to parse more eagerly than we compile.
-
-    // We can only parse lazily if we also compile lazily. The heuristics for
-    // lazy compilation are:
-    // - It must not have been prohibited by the caller to Parse (some callers
-    //   need a full AST).
-    // - The outer scope must allow lazy compilation of inner functions.
-    // - The function mustn't be a function expression with an open parenthesis
-    //   before; we consider that a hint that the function will be called
-    //   immediately, and it would be a waste of time to make it lazily
-    //   compiled.
-    // These are all things we can know at this point, without looking at the
-    // function itself.
-
-    // In addition, we need to distinguish between these cases:
-    // (function foo() {
-    //   bar = function() { return 1; }
-    //  })();
-    // and
-    // (function foo() {
-    //   var a = 1;
-    //   bar = function() { return a; }
-    //  })();
-
-    // Now foo will be parsed eagerly and compiled eagerly (optimization: assume
-    // parenthesis before the function means that it will be called
-    // immediately). The inner function *must* be parsed eagerly to resolve the
-    // possible reference to the variable in foo's scope. However, it's possible
-    // that it will be compiled lazily.
-
-    // To make this additional case work, both Parser and PreParser implement a
-    // logic where only top-level functions will be parsed lazily.
-    bool is_lazily_parsed = mode() == PARSE_LAZILY &&
-                            this->scope()->AllowsLazyParsing() &&
-                            !function_state_->this_function_is_parenthesized();
-
     // Eager or lazy parse?
     // If is_lazily_parsed, we'll parse lazy. If we can set a bookmark, we'll
     // pass it to SkipLazyFunctionBody, which may use it to abort lazy
@@ -4433,45 +4488,15 @@ FunctionLiteral* Parser::ParseFunctionLiteral(
       }
     }
     if (!is_lazily_parsed) {
-      // Determine whether the function body can be discarded after parsing.
-      // The preconditions are:
-      // - Lazy compilation has to be enabled.
-      // - Neither V8 natives nor native function declarations can be allowed,
-      //   since parsing one would retroactively force the function to be
-      //   eagerly compiled.
-      // - The invoker of this parser can't depend on the AST being eagerly
-      //   built (either because the function is about to be compiled, or
-      //   because the AST is going to be inspected for some reason).
-      // - Because of the above, we can't be attempting to parse a
-      //   FunctionExpression; even without enclosing parentheses it might be
-      //   immediately invoked.
-      // - The function literal shouldn't be hinted to eagerly compile.
-      // - For asm.js functions the body needs to be available when module
-      //   validation is active, because we examine the entire module at once.
-      bool use_temp_zone =
-          FLAG_lazy && !allow_natives() && extension_ == NULL && allow_lazy() &&
-          function_type == FunctionLiteral::kDeclaration &&
-          eager_compile_hint != FunctionLiteral::kShouldEagerCompile &&
-          !(FLAG_validate_asm && scope->asm_function());
-      // Open a new zone scope, which sets our AstNodeFactory to allocate in the
-      // new temporary zone if the preconditions are satisfied, and ensures that
-      // the previous zone is always restored after parsing the body.
-      // For the purpose of scope analysis, some ZoneObjects allocated by the
-      // factory must persist after the function body is thrown away and
-      // temp_zone is deallocated. These objects are instead allocated in a
-      // parser-persistent zone (see parser_zone_ in AstNodeFactory).
-      {
-        Zone temp_zone(zone()->allocator());
-        DiscardableZoneScope zone_scope(this, &temp_zone, use_temp_zone);
-        body = ParseEagerFunctionBody(function_name, pos, formals, kind,
-                                      function_type, CHECK_OK);
-      }
+      body = ParseEagerFunctionBody(function_name, pos, formals, kind,
+                                    function_type, CHECK_OK);
+
       materialized_literal_count = function_state.materialized_literal_count();
       expected_property_count = function_state.expected_property_count();
       if (use_temp_zone) {
         // If the preconditions are correct the function body should never be
         // accessed, but do this anyway for better behaviour if they're wrong.
-        body = NULL;
+        body = nullptr;
       }
     }
 
@@ -4501,14 +4526,20 @@ FunctionLiteral* Parser::ParseFunctionLiteral(
     }
     has_duplicate_parameters =
       !formals_classifier.is_valid_formal_parameter_list_without_duplicates();
-  }
+
+    if (use_temp_zone) {
+      DCHECK(main_scope != scope);
+      scope->AnalyzePartially(main_scope, &previous_zone_ast_node_factory);
+    }
+  }  // DiscardableZoneScope goes out of scope.
 
   FunctionLiteral::ParameterFlag duplicate_parameters =
       has_duplicate_parameters ? FunctionLiteral::kHasDuplicateParameters
                                : FunctionLiteral::kNoDuplicateParameters;
 
+  // Note that the FunctionLiteral needs to be created in the main Zone again.
   FunctionLiteral* function_literal = factory()->NewFunctionLiteral(
-      function_name, scope, body, materialized_literal_count,
+      function_name, main_scope, body, materialized_literal_count,
       expected_property_count, arity, duplicate_parameters, function_type,
       eager_compile_hint, kind, pos);
   function_literal->set_function_token_position(function_token_pos);