From 086fe2199ba7849113413a21ceb38d167eb74176 Mon Sep 17 00:00:00 2001
From: ishell <ishell@chromium.org>
Date: Tue, 26 Apr 2016 02:05:48 -0700
Subject: [PATCH] [es6] Fix tail call elimination in single-expression arrow
 functions.

BUG=v8:4698
LOG=Y

Review URL: https://codereview.chromium.org/1921083002

Cr-Commit-Position: refs/heads/master@{#35786}
---
 src/parsing/parser-base.h     |  4 ++++
 src/parsing/parser.cc         |  5 ++++-
 src/parsing/parser.h          |  2 ++
 src/parsing/preparser.h       |  2 ++
 test/mjsunit/es6/tail-call.js | 21 +++++++++++++++++++++
 5 files changed, 33 insertions(+), 1 deletion(-)

diff --git a/src/parsing/parser-base.h b/src/parsing/parser-base.h
index 868650afd9..530ce5aa18 100644
--- a/src/parsing/parser-base.h
+++ b/src/parsing/parser-base.h
@@ -2866,6 +2866,10 @@ ParserBase<Traits>::ParseArrowFunctionLiteral(
       body->Add(factory()->NewReturnStatement(expression, pos), zone());
       materialized_literal_count = function_state.materialized_literal_count();
       expected_property_count = function_state.expected_property_count();
+      // ES6 14.6.1 Static Semantics: IsInTailPosition
+      if (allow_tailcalls() && !is_sloppy(language_mode())) {
+        this->MarkTailPosition(expression);
+      }
     }
     super_loc = function_state.super_location();
 
diff --git a/src/parsing/parser.cc b/src/parsing/parser.cc
index 8bd525af12..6e05fcbb01 100644
--- a/src/parsing/parser.cc
+++ b/src/parsing/parser.cc
@@ -762,6 +762,9 @@ ClassLiteral* ParserTraits::ParseClassLiteral(
                                     name_is_strict_reserved, pos, ok);
 }
 
+void ParserTraits::MarkTailPosition(Expression* expression) {
+  expression->MarkTail();
+}
 
 Parser::Parser(ParseInfo* info)
     : ParserBase<ParserTraits>(info->zone(), &scanner_, info->stack_limit(),
@@ -4573,7 +4576,7 @@ ZoneList<Statement*>* Parser::ParseEagerFunctionBody(
   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();
+    MarkTailPosition(expressions_in_tail_position[i]);
   }
   return result;
 }
diff --git a/src/parsing/parser.h b/src/parsing/parser.h
index dab2f92c0a..3df630a4ef 100644
--- a/src/parsing/parser.h
+++ b/src/parsing/parser.h
@@ -572,6 +572,8 @@ class ParserTraits {
                                   bool name_is_strict_reserved, int pos,
                                   bool* ok);
 
+  V8_INLINE void MarkTailPosition(Expression* expression);
+
   V8_INLINE void CheckConflictingVarDeclarations(v8::internal::Scope* scope,
                                                  bool* ok);
 
diff --git a/src/parsing/preparser.h b/src/parsing/preparser.h
index e2b4edab0f..62581cf74d 100644
--- a/src/parsing/preparser.h
+++ b/src/parsing/preparser.h
@@ -887,6 +887,8 @@ class PreParserTraits {
                                         bool name_is_strict_reserved, int pos,
                                         bool* ok);
 
+  V8_INLINE void MarkTailPosition(PreParserExpression) {}
+
   PreParserExpressionList PrepareSpreadArguments(PreParserExpressionList list) {
     return list;
   }
diff --git a/test/mjsunit/es6/tail-call.js b/test/mjsunit/es6/tail-call.js
index 3df53230ff..318519b355 100644
--- a/test/mjsunit/es6/tail-call.js
+++ b/test/mjsunit/es6/tail-call.js
@@ -392,3 +392,24 @@ function f_153(expected_call_stack, a) {
   %OptimizeFunctionOnNextCall(test);
   test();
 })();
+
+
+// Test tail calls from arrow functions.
+(function () {
+  function g1(a) {
+    return (() => { return f_153([f_153, test]); })();
+  }
+
+  function g2(a) {
+    return (() => f_153([f_153, test]))();
+  }
+
+  function test() {
+    assertEquals(153, g1());
+    assertEquals(153, g2());
+  }
+  test();
+  test();
+  %OptimizeFunctionOnNextCall(test);
+  test();
+})();