06ee127b75
This changes the JSArrayIterator to always have only a single instance type, instead of the zoo of instance types that we had before, and which became less useful with the specification update to when "next" is loaded from the iterator now. This greatly simplifies the baseline implementation of the array iterator, which now only looks at the iterated object during %ArrayIteratorPrototype%.next invocations. In TurboFan we introduce a new JSCreateArrayIterator operator, that holds the IterationKind and get's the iterated object as input. When optimizing %ArrayIteratorPrototype%.next in the JSCallReducer, we check whether the receiver is a JSCreateArrayIterator, and if so, we try to infer maps for the iterated object from there. If we find any, we speculatively assume that these won't have changed during iteration (as we did before with the previous approach), and generate fast code for both JSArray and JSTypedArray iteration. Drive-by-fix: Drop the fast_array_iteration protector, it's not necessary anymore since we have the deoptimization guard bit in the JSCallReducer now. This addresses the performance cliff noticed in webpack 4. The minimal repro on the tracking bug goes from console.timeEnd: mono, 124.773000 console.timeEnd: poly, 670.353000 to console.timeEnd: mono, 118.709000 console.timeEnd: poly, 141.393000 so that's a 4.7x improvement. Also make presubmit happy by adding the missing #undef's. Bug: v8:7510, v7:7514 Change-Id: I79a46bfa2cd0f0710e09365ef72519b1bbb667b5 Reviewed-on: https://chromium-review.googlesource.com/946098 Reviewed-by: Sigurd Schneider <sigurds@chromium.org> Commit-Queue: Benedikt Meurer <bmeurer@chromium.org> Cr-Commit-Position: refs/heads/master@{#51725} |
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| benchmarks | ||
| build_overrides | ||
| docs | ||
| gni | ||
| include | ||
| infra | ||
| samples | ||
| src | ||
| test | ||
| testing | ||
| third_party | ||
| tools | ||
| .clang-format | ||
| .editorconfig | ||
| .git-blame-ignore-revs | ||
| .gitignore | ||
| .gn | ||
| .vpython | ||
| .ycm_extra_conf.py | ||
| AUTHORS | ||
| BUILD.gn | ||
| ChangeLog | ||
| CODE_OF_CONDUCT.md | ||
| codereview.settings | ||
| DEPS | ||
| LICENSE | ||
| LICENSE.fdlibm | ||
| LICENSE.strongtalk | ||
| LICENSE.v8 | ||
| LICENSE.valgrind | ||
| 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.