Allocate block scopes in block states when possible

src/parsing/preparser.cc

 // Copyright 2011 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 <cmath>
 
 #include "src/allocation.h"
 #include "src/base/logging.h"
 #include "src/conversions-inl.h"
 #include "src/conversions.h"
@@ skipping 287 matching lines @@
     return Statement::Default();
   }
   return ParseSubStatement(allow_function, ok);
 }
 
 PreParser::Statement PreParser::ParseScopedStatement(bool legacy, bool* ok) {
   if (is_strict(language_mode()) || peek() != Token::FUNCTION ||
       (legacy && allow_harmony_restrictive_declarations())) {
     return ParseSubStatement(kDisallowLabelledFunctionStatement, ok);
   } else {
-    Scope* body_scope = NewScope(BLOCK_SCOPE);
-    BlockState block_state(&scope_state_, body_scope);
+    BlockState block_state(&scope_state_);
     return ParseFunctionDeclaration(ok);
   }
 }
 
 PreParser::Statement PreParser::ParseSubStatement(
     AllowLabelledFunctionStatement allow_function, bool* ok) {
   // Statement ::
   //   Block
   //   VariableStatement
   //   EmptyStatement
@@ skipping 149 matching lines @@
   ParseClassLiteral(nullptr, name, scanner()->location(), is_strict_reserved,
                     pos, CHECK_OK);
   return Statement::Default();
 }
 
 
 PreParser::Statement PreParser::ParseBlock(bool* ok) {
   // Block ::
   //   '{' StatementList '}'
 
-  Scope* block_scope = NewScope(BLOCK_SCOPE);
   Expect(Token::LBRACE, CHECK_OK);
   Statement final = Statement::Default();
   {
-    BlockState block_state(&scope_state_, block_scope);
+    BlockState block_state(&scope_state_);
     while (peek() != Token::RBRACE) {
       final = ParseStatementListItem(CHECK_OK);
     }
   }
   Expect(Token::RBRACE, ok);
   return final;
 }
 
 
 PreParser::Statement PreParser::ParseVariableStatement(
@@ skipping 305 matching lines @@
 
 PreParser::Statement PreParser::ParseSwitchStatement(bool* ok) {
   // SwitchStatement ::
   //   'switch' '(' Expression ')' '{' CaseClause* '}'
 
   Expect(Token::SWITCH, CHECK_OK);
   Expect(Token::LPAREN, CHECK_OK);
   ParseExpression(true, CHECK_OK);
   Expect(Token::RPAREN, CHECK_OK);
 
-  Scope* cases_scope = NewScope(BLOCK_SCOPE);
   {
-    BlockState cases_block_state(&scope_state_, cases_scope);
+    BlockState cases_block_state(&scope_state_);
     Expect(Token::LBRACE, CHECK_OK);
     Token::Value token = peek();
     while (token != Token::RBRACE) {
       if (token == Token::CASE) {
         Expect(Token::CASE, CHECK_OK);
         ParseExpression(true, CHECK_OK);
       } else {
         Expect(Token::DEFAULT, CHECK_OK);
       }
       Expect(Token::COLON, CHECK_OK);
@@ skipping 38 matching lines @@
   ParseScopedStatement(true, ok);
   return Statement::Default();
 }
 
 
 PreParser::Statement PreParser::ParseForStatement(bool* ok) {
   // ForStatement ::
   //   'for' '(' Expression? ';' Expression? ';' Expression? ')' Statement
 
   // Create an in-between scope for let-bound iteration variables.
-  Scope* for_scope = NewScope(BLOCK_SCOPE);
   bool has_lexical = false;
 
-  BlockState block_state(&scope_state_, for_scope);
+  BlockState block_state(&scope_state_);
   Expect(Token::FOR, CHECK_OK);
   Expect(Token::LPAREN, CHECK_OK);
   if (peek() != Token::SEMICOLON) {
     ForEachStatement::VisitMode mode;
     if (peek() == Token::VAR || peek() == Token::CONST ||
         (peek() == Token::LET && IsNextLetKeyword())) {
       int decl_count;
       bool is_lexical;
       bool is_binding_pattern;
       Scanner::Location first_initializer_loc = Scanner::Location::invalid();
@@ skipping 66 matching lines @@
 
         if (mode == ForEachStatement::ITERATE) {
           ExpressionClassifier classifier(this);
           ParseAssignmentExpression(true, &classifier, CHECK_OK);
           RewriteNonPattern(&classifier, CHECK_OK);
         } else {
           ParseExpression(true, CHECK_OK);
         }
 
         Expect(Token::RPAREN, CHECK_OK);
-        Scope* body_scope = NewScope(BLOCK_SCOPE);
         {
-          BlockState block_state(&scope_state_, body_scope);
+          BlockState block_state(&scope_state_);
           ParseScopedStatement(true, CHECK_OK);
         }
         return Statement::Default();
       }
     }
   }
 
   // Parsed initializer at this point.
   Expect(Token::SEMICOLON, CHECK_OK);
 
   // If there are let bindings, then condition and the next statement of the
   // for loop must be parsed in a new scope.
   Scope* inner_scope = scope();
-  if (has_lexical) inner_scope = NewScopeWithParent(for_scope, BLOCK_SCOPE);
+  // TODO(verwaest): Allocate this through a ScopeState as well.
+  if (has_lexical) inner_scope = NewScopeWithParent(inner_scope, BLOCK_SCOPE);
 
   {
     BlockState block_state(&scope_state_, inner_scope);
 
     if (peek() != Token::SEMICOLON) {
       ParseExpression(true, CHECK_OK);
     }
     Expect(Token::SEMICOLON, CHECK_OK);
 
     if (peek() != Token::RPAREN) {
@@ skipping 57 matching lines @@
     Scope* catch_scope = NewScope(CATCH_SCOPE);
     ExpressionClassifier pattern_classifier(this);
     ParsePrimaryExpression(&pattern_classifier, CHECK_OK);
     ValidateBindingPattern(&pattern_classifier, CHECK_OK);
     Expect(Token::RPAREN, CHECK_OK);
     {
       CollectExpressionsInTailPositionToListScope
           collect_tail_call_expressions_scope(
               function_state_, &tail_call_expressions_in_catch_block);
       BlockState block_state(&scope_state_, catch_scope);
-      Scope* block_scope = NewScope(BLOCK_SCOPE);
       {
-        BlockState block_state(&scope_state_, block_scope);
+        BlockState block_state(&scope_state_);
         ParseBlock(CHECK_OK);
       }
     }
     catch_block_exists = true;
     tok = peek();
   }
   if (tok == Token::FINALLY) {
     Consume(Token::FINALLY);
     ParseBlock(CHECK_OK);
     if (FLAG_harmony_explicit_tailcalls && catch_block_exists &&
@@ skipping 154 matching lines @@
     *ok = false;
     return EmptyExpression();
   }
   if (IsEvalOrArguments(name)) {
     ReportMessageAt(class_name_location, MessageTemplate::kStrictEvalArguments);
     *ok = false;
     return EmptyExpression();
   }
 
   LanguageMode class_language_mode = language_mode();
-  Scope* scope = NewScope(BLOCK_SCOPE);
-  BlockState block_state(&scope_state_, scope);
-  this->scope()->SetLanguageMode(
+  BlockState block_state(&scope_state_);
+  scope()->SetLanguageMode(
       static_cast<LanguageMode>(class_language_mode | STRICT));
   // TODO(marja): Make PreParser use scope names too.
   // this->scope()->SetScopeName(name);
 
   bool has_extends = Check(Token::EXTENDS);
   if (has_extends) {
     ExpressionClassifier extends_classifier(this);
     ParseLeftHandSideExpression(&extends_classifier, CHECK_OK);
     CheckNoTailCallExpressions(&extends_classifier, CHECK_OK);
     ValidateExpression(&extends_classifier, CHECK_OK);
@@ skipping 74 matching lines @@
 
   body->Add(PreParserStatement::ExpressionStatement(return_value), zone());
 }
 
 #undef CHECK_OK
 #undef CHECK_OK_CUSTOM
 
 
 }  // namespace internal
 }  // namespace v8