[es6] Tail calls support.

test/mjsunit/es6/tail-call-simple.js

+// Copyright 2016 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.
+
+// Flags: --allow-natives-syntax --harmony-tailcalls --stack-size=100
+
+//
+// Tail calls work only in strict mode.
+//
+(function() {
+  function f(n) {
+    if (n <= 0) {
+      return  "foo";
+    }
+    return f(n - 1);
+  }
+  assertThrows(()=>{ f(1e6) });
+})();
+
+
+//
+// Tail call normal functions.
+//
+(function() {
+  "use strict";
+  function f(n) {
+    if (n <= 0) {
+      return  "foo";
+    }
+    return f(n - 1);
+  }
+  assertEquals("foo", f(1e6));
+})();
+
+
+(function() {
+  "use strict";
+  function f(n){
+    if (n <= 0) {
+      return "foo";
+    }
+    return g(n - 1);
+  }
+  function g(n){
+    if (n <= 0) {
+      return "bar";
+    }
+    return f(n - 1);
+  }
+  assertEquals("foo", f(1e6));
+  assertEquals("bar", f(1e6 + 1));
+})();
+
+
+//
+// Tail call bound functions.
+//
+(function() {
+  "use strict";
+  function f0(n) {
+    if (n <= 0) {
+      return "foo";
+    }
+    return f(n - 1);
+  }
+  var f = f0.bind({});
+  assertEquals("foo", f(1e6));
+})();
+
+
+(function() {
+  "use strict";
+  function f0(n){
+    if (n <= 0) {
+      return "foo";
+    }
+    return g(n - 1);
+  }
+  function g0(n){
+    if (n <= 0) {
+      return "bar";
+    }
+    return f(n - 1);
+  }
+  var f = f0.bind({});
+  var g = g0.bind({});
+
+  assertEquals("foo", f(1e6));
+  assertEquals("bar", f(1e6 + 1));
+})();