v8/test/mjsunit/regress/regress-4376-2.js
bmeurer 5d875a57fa Correctify instanceof and make it optimizable.
The previous hack with HInstanceOfKnownGlobal was not only slower,
but also very brittle and required a lot of weird hacks to support it. And
what's even more important it wasn't even correct (because a map check
on the lhs is never enough for instanceof).

The new implementation provides a sane runtime implementation
for InstanceOf plus a fast case in the InstanceOfStub, combined with
a proper specialization in the case of a known global in CrankShaft,
which does only the prototype chain walk (coupled with a code
dependency on the known global).

As a drive-by-fix: Also fix the incorrect Object.prototype.isPrototypeOf
implementation.

BUG=v8:4376
LOG=y

Review URL: https://codereview.chromium.org/1304633002

Cr-Commit-Position: refs/heads/master@{#30342}
2015-08-25 04:48:54 +00:00

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298 B
JavaScript

// 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.
function Foo() {}
var x = new Foo();
Foo.prototype = 1;
function foo() { return x instanceof Foo; }
assertThrows(foo, TypeError);