[es6] More efficient way of marking AST call expressions in tail positions.

src/parsing/parser.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/parsing/parser.h"
 
 #include "src/api.h"
 #include "src/ast/ast.h"
 #include "src/ast/ast-expression-rewriter.h"
 #include "src/ast/ast-expression-visitor.h"
@@ skipping 2774 matching lines @@
       // temp === undefined
       Expression* is_undefined = factory()->NewCompareOperation(
           Token::EQ_STRICT, assign,
           factory()->NewUndefinedLiteral(RelocInfo::kNoPosition), pos);
 
       // is_undefined ? this : is_object_conditional
       return_value = factory()->NewConditional(
           is_undefined, ThisExpression(scope_, factory(), pos),
           is_object_conditional, pos);
     }
+
+    // ES6 14.6.1 Static Semantics: IsInTailPosition
+    if (FLAG_harmony_tailcalls && !is_sloppy(language_mode())) {
+      function_state_->AddExpressionInTailPosition(return_value);
+    }
   }
   ExpectSemicolon(CHECK_OK);
 
   if (is_generator()) {
     Expression* generator = factory()->NewVariableProxy(
         function_state_->generator_object_variable());
     Expression* yield = factory()->NewYield(
         generator, return_value, Yield::kFinal, loc.beg_pos);
     result = factory()->NewExpressionStatement(yield, loc.beg_pos);
   } else {
@@ skipping 185 matching lines @@
     *ok = false;
     return NULL;
   }
   Expression* exception = ParseExpression(true, CHECK_OK);
   ExpectSemicolon(CHECK_OK);
 
   return factory()->NewExpressionStatement(
       factory()->NewThrow(exception, pos), pos);
 }
 
+class Parser::DontCollectExpressionsInTailPositionScope {
+ public:
+  DontCollectExpressionsInTailPositionScope(
+      Parser::FunctionState* function_state)
+      : function_state_(function_state),
+        old_value_(function_state->collect_expressions_in_tail_position()) {
+    function_state->set_collect_expressions_in_tail_position(false);
+  }
+  ~DontCollectExpressionsInTailPositionScope() {
+    function_state_->set_collect_expressions_in_tail_position(old_value_);
+  }
+
+ private:
+  Parser::FunctionState* function_state_;
+  bool old_value_;
+};
+
+// Collects all return expressions at tail call position in this scope
+// to a separate list.
+class Parser::CollectExpressionsInTailPositionToListScope {
+ public:
+  CollectExpressionsInTailPositionToListScope(
+      Parser::FunctionState* function_state, List<Expression*>* list)
+      : function_state_(function_state), list_(list) {
+    function_state->expressions_in_tail_position().Swap(list_);
+  }
+  ~CollectExpressionsInTailPositionToListScope() {
+    function_state_->expressions_in_tail_position().Swap(list_);
+  }
+
+ private:
+  Parser::FunctionState* function_state_;
+  List<Expression*>* list_;
+};
 
 TryStatement* Parser::ParseTryStatement(bool* ok) {
   // TryStatement ::
   //   'try' Block Catch
   //   'try' Block Finally
   //   'try' Block Catch Finally
   //
   // Catch ::
   //   'catch' '(' Identifier ')' Block
   //
   // Finally ::
   //   'finally' Block
 
   Expect(Token::TRY, CHECK_OK);
   int pos = position();
 
-  Block* try_block = ParseBlock(NULL, CHECK_OK);
+  Block* try_block;
+  {
+    DontCollectExpressionsInTailPositionScope no_tail_calls(function_state_);
+    try_block = ParseBlock(NULL, CHECK_OK);
+  }
 
   Token::Value tok = peek();
   if (tok != Token::CATCH && tok != Token::FINALLY) {
     ReportMessage(MessageTemplate::kNoCatchOrFinally);
     *ok = false;
     return NULL;
   }
 
   Scope* catch_scope = NULL;
   Variable* catch_variable = NULL;
   Block* catch_block = NULL;
+  List<Expression*> expressions_in_tail_position_in_catch_block;
   if (tok == Token::CATCH) {
     Consume(Token::CATCH);
 
     Expect(Token::LPAREN, CHECK_OK);
     catch_scope = NewScope(scope_, CATCH_SCOPE);
     catch_scope->set_start_position(scanner()->location().beg_pos);
 
     ExpressionClassifier pattern_classifier;
     Expression* pattern = ParsePrimaryExpression(&pattern_classifier, CHECK_OK);
     ValidateBindingPattern(&pattern_classifier, CHECK_OK);
 
     const AstRawString* name = ast_value_factory()->dot_catch_string();
     bool is_simple = pattern->IsVariableProxy();
     if (is_simple) {
       auto proxy = pattern->AsVariableProxy();
       scope_->RemoveUnresolved(proxy);
       name = proxy->raw_name();
     }
 
     catch_variable = catch_scope->DeclareLocal(name, VAR, kCreatedInitialized,
                                                Variable::NORMAL);
 
     Expect(Token::RPAREN, CHECK_OK);
 
     {
+      CollectExpressionsInTailPositionToListScope
+          collect_expressions_in_tail_position_scope(
+              function_state_, &expressions_in_tail_position_in_catch_block);
       BlockState block_state(&scope_, catch_scope);
 
       // TODO(adamk): Make a version of ParseBlock that takes a scope and
       // a block.
       catch_block =
           factory()->NewBlock(nullptr, 16, false, RelocInfo::kNoPosition);
       Scope* block_scope = NewScope(scope_, BLOCK_SCOPE);
 
       block_scope->set_start_position(scanner()->location().beg_pos);
       {
@@ skipping 54 matching lines @@
     TryCatchStatement* statement =
         factory()->NewTryCatchStatement(try_block, catch_scope, catch_variable,
                                         catch_block, RelocInfo::kNoPosition);
     try_block = factory()->NewBlock(NULL, 1, false, RelocInfo::kNoPosition);
     try_block->statements()->Add(statement, zone());
     catch_block = NULL;  // Clear to indicate it's been handled.
   }
 
   TryStatement* result = NULL;
   if (catch_block != NULL) {
+    // For a try-catch construct append return expressions from the catch block
+    // to the list of return expressions.
+    function_state_->expressions_in_tail_position().AddAll(
+        expressions_in_tail_position_in_catch_block);
+
     DCHECK(finally_block == NULL);
     DCHECK(catch_scope != NULL && catch_variable != NULL);
     result = factory()->NewTryCatchStatement(try_block, catch_scope,
                                              catch_variable, catch_block, pos);
   } else {
     DCHECK(finally_block != NULL);
     result = factory()->NewTryFinallyStatement(try_block, finally_block, pos);
   }
 
   return result;
@@ skipping 1607 matching lines @@
     VariableProxy* fproxy = factory()->NewVariableProxy(fvar);
     result->Set(kFunctionNameAssignmentIndex,
                 factory()->NewExpressionStatement(
                     factory()->NewAssignment(Token::INIT, fproxy,
                                              factory()->NewThisFunction(pos),
                                              RelocInfo::kNoPosition),
                     RelocInfo::kNoPosition));
   }
 
   // ES6 14.6.1 Static Semantics: IsInTailPosition
-  if (FLAG_harmony_tailcalls && !is_sloppy(language_mode())) {
-    for (int i = 0; i < body->length(); i++) {
-      Statement* stmt = body->at(i);
-      stmt->MarkTail();
-    }
+  // Mark collected return expressions that are in tail call position.
+  const List<Expression*>& expressions_in_tail_position =
+      function_state_->expressions_in_tail_position();
+  for (int i = 0; i < expressions_in_tail_position.length(); ++i) {
+    expressions_in_tail_position[i]->MarkTail();
   }
   return result;
 }
 
 
 PreParser::PreParseResult Parser::ParseLazyFunctionBodyWithPreParser(
     SingletonLogger* logger, Scanner::BookmarkScope* bookmark) {
   // This function may be called on a background thread too; record only the
   // main thread preparse times.
   if (pre_parse_timer_ != NULL) {
@@ skipping 1561 matching lines @@
 
   statements->Add(get_return, zone);
   statements->Add(check_return, zone);
   statements->Add(call_return, zone);
   statements->Add(validate_output, zone);
 }
 
 
 }  // namespace internal
 }  // namespace v8