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Benedikt Meurer b8b76ebaac [es2015] Optimize TypedArray.prototype[Symbol.toStringTag]. 
The TypedArray.prototype[Symbol.toStringTag] getter is currently the best (and
as far as I can tell only definitely side-effect free) way to check whether an
arbitrary object is a TypedArray - either generally TypedArray or a specific
one like Uint8Array. Using the getter is thus emerging as the general pattern
to detect TypedArrays, even Node.js now adapted it starting with

  https://github.com/nodejs/node/pull/15663

for the isTypedArray and isUint8Array type checks in lib/internal/util/types.js
now.

The getter returns either the string with the TypedArray subclass name
(i.e. "Uint8Array") or undefined if the receiver is not a TypedArray.
This can be implemented with a simple elements kind dispatch, instead of
checking the instance type and then loading the class name from the
constructor, which requires a loop walking up the transition tree. This
CL ports the builtin to CSA and TurboFan, and changes the logic to a
simple elements kind check. On the micro-benchmark mentioned in the
referenced bug, the time goes from

  testIsArrayBufferView: 565 ms.
  testIsTypedArray: 2403 ms.
  testIsUint8Array: 3847 ms.

to

  testIsArrayBufferView: 566 ms.
  testIsTypedArray: 965 ms.
  testIsUint8Array: 965 ms.

which presents an up to 4x improvement.

Bug: v8:6874
Change-Id: I9c330b4529d9631df2f052acf023c6a4fae69611
Reviewed-on: https://chromium-review.googlesource.com/695021
Reviewed-by: Jaroslav Sevcik <jarin@chromium.org>
Commit-Queue: Benedikt Meurer <bmeurer@chromium.org>
Cr-Commit-Position: refs/heads/master@{#48254}
2017-10-02 07:12:49 +00:00
benchmarks Fix common misspellings 2017-08-02 09:35:28 +00:00
build_overrides Remove build_override for macOS min SDK and deployment target. 2017-07-14 18:24:44 +00:00
docs [Docs] Removed unused docs because they are moved to GitHub 2015-11-19 10:23:30 +00:00
gni Reland "[build] Switch windows default compilation to MSVS 2017" 2017-09-29 09:36:49 +00:00
gypfiles [heap] Enable concurrent marking on all platforms. 2017-09-29 11:38:50 +00:00
include [snapshot] add kProduceExhaustiveCodeCache option. 2017-09-26 09:53:53 +00:00
infra [build] Add MB config for win64 asan bots 2017-08-16 14:01:31 +00:00
samples [presubmit] Enable and fix "build/namespaces" linter check. 2017-09-04 11:24:26 +00:00
src [es2015] Optimize TypedArray.prototype[Symbol.toStringTag]. 2017-10-02 07:12:49 +00:00
test [es2015] Optimize TypedArray.prototype[Symbol.toStringTag]. 2017-10-02 07:12:49 +00:00
testing Use GTEST_LANG_CXX11 in V8 2016-07-25 13:06:42 +00:00
third_party [build] Port "Add patched eu-strip in third_party" 2017-09-25 09:52:23 +00:00
tools Reland "[build] Switch windows default compilation to MSVS 2017" 2017-09-29 09:36:49 +00:00
.clang-format [clang-format] Don't derive pointer alignment 2017-01-17 09:28:19 +00:00
.editorconfig Add .editorconfig 2017-07-28 13:39:24 +00:00
.gitignore [build] Port "Add patched eu-strip in third_party" 2017-09-25 09:52:23 +00:00
.gn For building v8 using gn on aix_ppc64, linux_s390x and linux_ppc64(both LE and BE). 2017-05-12 01:35:09 +00:00
.ycm_extra_conf.py Use C++11 / gnu++11, not 0x 2016-03-22 15:24:43 +00:00
AUTHORS Update AUTHORS file for Vewd Software 2017-09-28 17:25:36 +00:00
BUILD.gn [heap] Enable concurrent marking on all platforms. 2017-09-29 11:38:50 +00:00
ChangeLog [Release] Update ChangeLog file 2016-02-17 21:29:09 +00:00
CODE_OF_CONDUCT.md Explicitly state that the Chromium Code of Conduct also applies to V8 2016-03-02 09:51:24 +00:00
codereview.settings Make Gerrit the default code review for V8 2017-06-30 17:37:37 +00:00
DEPS Update V8 DEPS. 2017-10-02 03:52:21 +00:00
LICENSE Updates to the license information of third party components. 2015-06-16 12:37:50 +00:00
LICENSE.fdlibm Add LICENSE.fdlibm for all the fdlibm imported sources. 2016-06-09 07:17:03 +00:00
LICENSE.strongtalk Add LICENSE.v8, LICENSE.strongtalk and LICENSE.valgrind to the v8 2011-02-03 07:10:06 +00:00
LICENSE.v8 Add LICENSE.v8, LICENSE.strongtalk and LICENSE.valgrind to the v8 2011-02-03 07:10:06 +00:00
LICENSE.valgrind Add LICENSE.v8, LICENSE.strongtalk and LICENSE.valgrind to the v8 2011-02-03 07:10:06 +00:00
Makefile [heap] Port concurrent marking flag to GYP. 2017-08-23 15:26:43 +00:00
Makefile.android [build] Fix d8-for-Android builds 2016-05-20 12:10:45 +00:00
OWNERS Add eholk and gdeepti to toplevel owners 2017-08-12 07:07:29 +00:00
PRESUBMIT.py [iwyu] Turn inclusion presubmit warning into and error. 2017-09-14 10:17:58 +00:00
README.md [Docs] Removed unused docs because they are moved to GitHub 2015-11-19 10:23:30 +00:00
snapshot_toolchain.gni MIPS[64]: Add support for big endian build using GN 2017-06-02 15:02:18 +00:00
WATCHLISTS [V8Tracing] Add lpy@ and fmeawad@ into watchlist for tracing/. 2017-05-22 19:40:17 +00:00

README.md

V8 JavaScript Engine

V8 is Google's open source JavaScript engine.

V8 implements ECMAScript as specified in ECMA-262.

V8 is written in C++ and is used in Google Chrome, the open source browser from Google.

V8 can run standalone, or can be embedded into any C++ application.

V8 Project page: https://github.com/v8/v8/wiki

Getting the Code

Checkout depot tools, and run

    fetch v8

This will checkout V8 into the directory v8 and fetch all of its dependencies. To stay up to date, run

    git pull origin
    gclient sync

For fetching all branches, add the following into your remote configuration in .git/config:

    fetch = +refs/branch-heads/*:refs/remotes/branch-heads/*
    fetch = +refs/tags/*:refs/tags/*

Contributing

Please follow the instructions mentioned on the V8 wiki.