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Benedikt Meurer 50f713c9a2 [promises] Add fast-path for native promises to Promise.all. 
This CL introduces a new fast-path for `Promise.all(a)` for the case
that elements in `a` are native promises, and the Promise.prototype
and Promise function itself are intact. If so, we can skip the lookups
of "resolve" on Promise and "then" on the result of invoking "resolve",
which are both quite expensive, and we can instead directly call the
PerformPromiseThen() operation on the element of `a`.

In addition to that we don't need to create and chain a result promise,
since this is only used when either async_hooks or DevTools are enabled.
Otherwise it's a "throwaway promise" only used to satisfy the operation
parameter signature (see https://github.com/tc39/ecma262/pull/1146).

This results in a significant performance improvement on `Promise.all()`
heavy code. For example the parallel-promises-es2015-native test goes
from around 84ms to roughly 68ms, which is almost a 20% improvement.

Bug: v8:7253
Ref: tc39/ecma262#1146
Change-Id: Iab9c57edb26d13a467b0653fd8de6149c382efc6
Reviewed-on: https://chromium-review.googlesource.com/c/1293374
Reviewed-by: Sathya Gunasekaran <gsathya@chromium.org>
Reviewed-by: Maya Lekova <mslekova@chromium.org>
Commit-Queue: Benedikt Meurer <bmeurer@chromium.org>
Cr-Commit-Position: refs/heads/master@{#56858}
2018-10-22 14:35:50 +00:00
benchmarks Reland: [builtins] Implement Array.prototype.slice in Torque 2018-10-19 21:27:19 +00:00
build_overrides [ndk] Change android ndk root for v8 2018-01-11 08:10:33 +00:00
custom_deps [build] Add common directory for custom deps 2018-06-08 19:23:02 +00:00
docs [Docs] Removed unused docs because they are moved to GitHub 2015-11-19 10:23:30 +00:00
gni [build] disable asan on Windows for Torque 2018-10-10 11:47:40 +00:00
include [heap] Reclaim inaccessible memory. 2018-10-22 10:21:57 +00:00
infra [test] Migrate test configs for ports console 2018-10-19 09:10:22 +00:00
samples Add a sample that uses the JS API to create wasm 2018-06-07 23:43:38 +00:00
src [promises] Add fast-path for native promises to Promise.all. 2018-10-22 14:35:50 +00:00
test Revert "[js weak refs] Add WeakCell.clear()" 2018-10-22 14:16:52 +00:00
testing Remove dummy files created for rolling googletest. 2018-03-27 05:55:56 +00:00
third_party Reland: [builtins] Implement Array.prototype.slice in Torque 2018-10-19 21:27:19 +00:00
tools [tools] Always set --data-path for content_shell 2018-10-22 14:19:35 +00:00
.clang-format [clang-format] Don't derive pointer alignment 2017-01-17 09:28:19 +00:00
.clang-tidy Add a tool/script to run clang-tidy over V8. 2018-09-11 12:01:09 +00:00
.editorconfig Add .editorconfig 2017-07-28 13:39:24 +00:00
.git-blame-ignore-revs [build] Add DEPS formatting to hyper-blame 2017-10-09 14:08:45 +00:00
.gitattributes .gitattributes: Mark minified emscripten js files as -diff 2018-09-19 16:27:10 +00:00
.gitignore Reland "[wasm] Add a new wasm-js testsuite to run js-api tests" 2018-10-18 20:18:55 +00:00
.gn [test] Remove obsolete test262 archive extract 2018-03-28 13:52:15 +00:00
.vpython [tools] Add VPython config for callstats.py 2018-08-14 10:15:46 +00:00
.ycm_extra_conf.py [ycm] Switch from gnu++11 to gnu++14 2017-11-27 07:48:21 +00:00
AUTHORS [postmortem] add postmortem metadata for Promises 2018-10-10 11:25:45 +00:00
BUILD.gn [tools] Add lite_mode status file parameter. 2018-10-22 10:15:10 +00:00
ChangeLog [tools] Merge ChangeLog from latest release 2017-12-19 12:30:56 +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. 2018-10-22 04:25:13 +00:00
LICENSE Add antlr4 runtime library to support Torque 2018-04-10 10:01:01 +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
OWNERS Reduce wasm OWNERS to current team members 2018-10-15 14:47:49 +00:00
PRESUBMIT.py Fix nits in presubmit.py and handling of .tq otherwise formatting 2018-09-25 15:37:39 +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]: Generate snapshots on MIPS big-endian targets 2017-11-24 19:00:32 +00:00
WATCHLISTS Make my watchlists easier to filter 2018-08-30 15:28:02 +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.