[es8] Initial set of changes to support syntactic tail calls.

test/mjsunit/es7/syntactic-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
+// Flags: --allow-natives-syntax --harmony-explicit-tailcalls --stack-size=100
 
 //
-// Tail calls work only in strict mode.
+// Tail call normal functions.
 //
 (function() {
   function f(n) {
     if (n <= 0) {
       return "foo";
     }
-    return f(n - 1);
-  }
-  assertThrows(()=>{ f(1e5) });
-  %OptimizeFunctionOnNextCall(f);
-  assertThrows(()=>{ f(1e5) });
-})();
-
-
-//
-// Tail call normal functions.
-//
-(function() {
-  "use strict";
-  function f(n) {
-    if (n <= 0) {
-      return "foo";
-    }
-    return f(n - 1);
+    return continue f(n - 1);
   }
   assertEquals("foo", f(1e5));
   %OptimizeFunctionOnNextCall(f);
   assertEquals("foo", f(1e5));
 })();
 
 
 (function() {
-  "use strict";
   function f(n) {
     if (n <= 0) {
       return  "foo";
     }
-    return f(n - 1, 42);  // Call with arguments adaptor.
+    return continue f(n - 1, 42);  // Call with arguments adaptor.
   }
   assertEquals("foo", f(1e5));
   %OptimizeFunctionOnNextCall(f);
   assertEquals("foo", f(1e5));
 })();
 
 
 (function() {
-  "use strict";
   function f(n){
     if (n <= 0) {
       return "foo";
     }
-    return g(n - 1);
+    return continue g(n - 1);
   }
   function g(n){
     if (n <= 0) {
       return "bar";
     }
-    return f(n - 1);
+    return continue f(n - 1);
   }
   assertEquals("foo", f(1e5));
   assertEquals("bar", f(1e5 + 1));
   %OptimizeFunctionOnNextCall(f);
   assertEquals("foo", f(1e5));
   assertEquals("bar", f(1e5 + 1));
 })();
 
 
 (function() {
-  "use strict";
   function f(n){
     if (n <= 0) {
       return "foo";
     }
-    return g(n - 1, 42);  // Call with arguments adaptor.
+    return continue g(n - 1, 42);  // Call with arguments adaptor.
   }
   function g(n){
     if (n <= 0) {
       return "bar";
     }
-    return f(n - 1, 42);  // Call with arguments adaptor.
+    return continue f(n - 1, 42);  // Call with arguments adaptor.
   }
   assertEquals("foo", f(1e5));
   assertEquals("bar", f(1e5 + 1));
   %OptimizeFunctionOnNextCall(f);
   assertEquals("foo", f(1e5));
   assertEquals("bar", f(1e5 + 1));
 })();
 
 
 //
 // Tail call bound functions.
 //
 (function() {
-  "use strict";
   function f0(n) {
     if (n <= 0) {
       return "foo";
     }
-    return f_bound(n - 1);
+    return continue f_bound(n - 1);
   }
   var f_bound = f0.bind({});
   function f(n) {
-    return f_bound(n);
+    return continue f_bound(n);
   }
   assertEquals("foo", f(1e5));
   %OptimizeFunctionOnNextCall(f);
   assertEquals("foo", f(1e5));
 })();
 
 
 (function() {
-  "use strict";
   function f0(n){
     if (n <= 0) {
       return "foo";
     }
-    return g_bound(n - 1);
+    return continue g_bound(n - 1);
   }
   function g0(n){
     if (n <= 0) {
       return "bar";
     }
-    return f_bound(n - 1);
+    return continue f_bound(n - 1);
   }
   var f_bound = f0.bind({});
   var g_bound = g0.bind({});
   function f(n) {
-    return f_bound(n);
+    return continue f_bound(n);
   }
   assertEquals("foo", f(1e5));
   assertEquals("bar", f(1e5 + 1));
   %OptimizeFunctionOnNextCall(f);
   assertEquals("foo", f(1e5));
   assertEquals("bar", f(1e5 + 1));
 })();