Do not reduce effect phis of loops.

test/mjsunit/compiler/regress-ntl-effect.js

Index: test/mjsunit/compiler/regress-ntl-effect.js
diff --git a/test/mjsunit/regress/regress-crbug-387636.js b/test/mjsunit/compiler/regress-ntl-effect.js
similarity index 51%
copy from test/mjsunit/regress/regress-crbug-387636.js
copy to test/mjsunit/compiler/regress-ntl-effect.js
index 1e50ace45a293c8561042f1a09c8fcd505b43dc2..708fe32828c9197dfa3d8c371ab01cbc1ad3317a 100644
--- a/test/mjsunit/regress/regress-crbug-387636.js
+++ b/test/mjsunit/compiler/regress-ntl-effect.js
@@ -1,14 +1,16 @@
-// Copyright 2014 the V8 project authors. All rights reserved.
+// Copyright 2015 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
 
+function g() {
+  throw 0;
+}
+
 function f() {
-  [].indexOf(0x40000000);
+  g();
+  while (1) {}
 }
 
-f();
-f();
-%OptimizeFunctionOnNextCall(f);
-f();
+assertThrows(function () { f(); });