v8/test/mjsunit/regress/regress-crbug-879560.js

// Copyright 2018 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() {
  var x = 1;
  x = undefined;
  while (x--)
    ;
};
%PrepareFunctionForOptimization(foo);
foo();
%OptimizeFunctionOnNextCall(foo);
foo();