v8/test/mjsunit/regress/regress-ensure-initial-map.js

// 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

var x = Object.getOwnPropertyDescriptor({get x() {}}, 'x').get;
function f(o, b) {
  if (b) {
    return o instanceof x;
  }
};
%PrepareFunctionForOptimization(f);
%OptimizeFunctionOnNextCall(f);
f();

function g() {
  return new x();
};
%PrepareFunctionForOptimization(g);
%OptimizeFunctionOnNextCall(g);
assertThrows(() => g());