[turbofan] Eliminate checkpoints before return in common op reducer.

test/mjsunit/compiler/regress-628773.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: --harmony-explicit-tailcalls
+// Flags: --harmony-tailcalls
+
 "use strict";
 
-function f() {
-  return 1;
+function foo() {
+  for  (var i = 0; i < 10000; i++) {
+    try {
+      for (var j = 0; j < 2; j++) {
+      }
+      throw 1;
+    } catch(e) {
+      if (typeof a == "number") return a && isNaN(b);
+    }
+  }
 }
 
-function g() {
-  try {
-    try {
-      f();
-    } catch(e) {
-      return continue f()  ;
-    }
-  } finally {
-    f();
-  }
-}
+foo();