06753c64eb
Optimize the common pattern
for (var i in o) {
if (Object.prototype.hasOwnProperty.call(o, i)) {
// do something
}
}
which is part of the guard-for-in style in ESLint (see the documentation
at https://eslint.org/docs/rules/guard-for-in for details). This pattern
also shows up in React and Ember applications quite a lot (and is tested
by the appropriate Speedometer benchmarks, although not dominating those
benchmarks, since they spent a lot of time in non-TurboFan'ed code).
This improves the forInHasOwnProperty and forInHasOwnPropertySafe micro-
benchmarks in v8:6702, which look like this
function forInHasOwnProperty(o) {
var result = 0;
for (var i in o) {
if (o.hasOwnProperty(i)) {
result += 1;
}
}
return result;
}
function forInHasOwnPropertySafe(o) {
var result = 0;
for (var i in o) {
if (Object.prototype.hasOwnProperty.call(o, i)) {
result += 1;
}
}
return result;
}
by around 4x and allows for additional optimizations in the future, by
also elimiating the megamorphic load when accessing the enumerated
properties.
This changes the interpreter ForInNext bytecode to collect more precise
feedback about the for-in state, which now consists of three individual
states: UNINITIALIZED, MEGAMORPHIC and GENERIC. The MEGAMORPHIC state
means that the ForInNext has only seen objects with a usable enum cache
thus far, whereas GENERIC means that we have seen some slow-mode for..in
objects as well.
R=jarin@chromium.org
Bug: v8:6702
Change-Id: Ibcd75ea9b58c3b4f9219f11bc37eb04a2b985604
Reviewed-on: https://chromium-review.googlesource.com/636964
Commit-Queue: Benedikt Meurer <bmeurer@chromium.org>
Reviewed-by: Jaroslav Sevcik <jarin@chromium.org>
Cr-Commit-Position: refs/heads/master@{#47632}
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| benchmarks | ||
| build_overrides | ||
| docs | ||
| gni | ||
| gypfiles | ||
| include | ||
| infra | ||
| samples | ||
| src | ||
| test | ||
| testing | ||
| third_party | ||
| tools | ||
| .clang-format | ||
| .editorconfig | ||
| .gitignore | ||
| .gn | ||
| .ycm_extra_conf.py | ||
| AUTHORS | ||
| BUILD.gn | ||
| ChangeLog | ||
| CODE_OF_CONDUCT.md | ||
| codereview.settings | ||
| DEPS | ||
| LICENSE | ||
| LICENSE.fdlibm | ||
| LICENSE.strongtalk | ||
| LICENSE.v8 | ||
| LICENSE.valgrind | ||
| Makefile | ||
| Makefile.android | ||
| OWNERS | ||
| PRESUBMIT.py | ||
| README.md | ||
| snapshot_toolchain.gni | ||
| WATCHLISTS | ||
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.