[turbofan] Fix lowering of Number.isNaN().

test/mjsunit/regress/regress-6082.js

Index: test/mjsunit/regress/regress-6082.js
diff --git a/test/mjsunit/regress/regress-6082.js b/test/mjsunit/regress/regress-6082.js
new file mode 100644
index 0000000000000000000000000000000000000000..aec1be0fb78f93795e9b8c7839f82d1cac1522cb
--- /dev/null
+++ b/test/mjsunit/regress/regress-6082.js
@@ -0,0 +1,11 @@
+// Copyright 2017 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 foo() { return Number.isNaN(); }
+assertFalse(foo());
+assertFalse(foo());
+%OptimizeFunctionOnNextCall(foo);
+assertFalse(foo());