[typedarrays] Use internal byteOffset in TypedArray.prototype.set

test/mjsunit/es6/typedarray-set-byteoffset-internal.js

+// Copyright 2016 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.
+
+var typedArrayConstructors = [
+  Uint8Array,
+  Int8Array,
+  Uint16Array,
+  Int16Array,
+  Uint32Array,
+  Int32Array,
+  Uint8ClampedArray,
+  Float32Array,
+  Float64Array
+];
+
+var descriptor = { get: function() { throw new Error("accessed byteOffset"); } };
+
+for (var constructor of typedArrayConstructors) {
+  var differentConstructor =
+    constructor === Uint8Array ? Int8Array : Uint8Array;
+  var target = new constructor(16);
+  Object.defineProperty(target, "byteOffset", descriptor);
+
+  var sameBuffer = new differentConstructor(target.buffer, 0, 2);
+  Object.defineProperty(sameBuffer, "byteOffset", descriptor);
+  target.set(sameBuffer);
+
+  var differentBuffer = new differentConstructor(16);
+  Object.defineProperty(differentBuffer, "byteOffset", descriptor);
+  target.set(differentBuffer);
+
+  var array = [0, 1, 2];
+  target.set(array);
+}

[Dan Ehrenberg, 2017/04/03 09:39:24]

These tests are great. Nit: Please cross-reference the bug that this is a
regression test for, either in a comment in this test file, or by naming it
test/mjsunit/regress-6120.js.

What would be even greater is upstream test262 tests so that other JS engine
vendors can also run them. You can put a test in the directory
test/test262/local-test ; find more information at
https://docs.google.com/document/d/16bj7AIDgZLv4WOsUEzQ5NzcEN9_xo095e88Pz8FC5...
if you want to write the test in this patch. Or, if you want to just check in
this version of the test, you could contribute a separate upstream test262 test
directly at https://github.com/tc39/test262/ . In the description field, you can
cross-reference the V8 bug.

[Choongwoo Han, 2017/04/03 11:43:38]

I cannot fully understand the process of the test262. Is the following my
understanding right?
1. put the test only into test/test262/local-test (not in mjsunit)
2. land this CL
3. make a PR to upstream
4. remove local-test (with another CL?) when it is merged into upstream