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I made some temporary changes in BytecodeArrayWriter to log counts of how often each pair of bytecodes is adjacent. In data I collected on a Facebook page with those changes enabled, I noticed that the following bytecodes were commonly followed by Star, but do not appear in IsStarLookahead. LdaImmutableCurrentContextSlot: 4.4% of all instructions, 66% chance to be followed by Star CreateClosure: 3.9% of all instructions, 57% chance to be followed by Star LdaImmutableContextSlot: 1.7% of all instructions, 95% chance to be followed by Star CreateObjectLiteral: 1.4% of all instructions, 92% chance to be followed by Star CreateArrayLiteral: 1.4% of all instructions, 99% chance to be followed by Star ThrowReferenceErrorIfHole: 0.7% of all instructions, 100% chance to be followed by Star GetTemplateObject: 0.6% of all instructions, 100% chance to be followed by Star CreateEmptyArrayLiteral: 0.4% of all instructions, 87% chance to be followed by Star CreateEmptyObjectLiteral: 0.2% of all instructions, 79% chance to be followed by Star I cross-referenced this list with data from google.com and youtube.com (the top two sites according to Alexa), and found that CreateClosure and CreateEmpty*Literal are not likely followed by Star on those sites. Without those three, I suggest that the following bytecode handlers would likely benefit from Star lookahead: LdaImmutableCurrentContextSlot LdaImmutableContextSlot CreateObjectLiteral CreateArrayLiteral ThrowReferenceErrorIfHole GetTemplateObject I also ran Octane with --noopt and got the following results. Name Median change (95% CI) U test result ----------------- ------------------------ ------------------- Richards +1.02% to +3.28% improved p=1.8e-05 DeltaBlue -1.47% to +0.12% regressed p=0.05 Crypto -1.11% to +0.93% inconclusive RayTrace -1.10% to +0.48% inconclusive EarleyBoyer -0.25% to +1.29% inconclusive RegExp -1.46% to +0.08% inconclusive Splay -1.10% to +0.03% inconclusive SplayLatency +0.13% to +0.92% improved p=5.8e-05 NavierStokes -0.22% to +1.24% inconclusive PdfJS -0.69% to +1.04% inconclusive Mandreel -0.66% to +0.66% inconclusive MandreelLatency +0.32% to +1.77% improved p=0.00024 Gameboy -1.13% to +0.38% inconclusive CodeLoad -0.27% to +0.43% inconclusive Box2D -0.53% to +0.82% inconclusive zlib -0.19% to +0.19% inconclusive Typescript -0.23% to +0.59% inconclusive Score (version 9) -0.18% to +0.68% inconclusive I'm somewhat puzzled by the DeltaBlue regression, since DeltaBlue agrees that all of the selected bytecodes are likely to precede Star, but overall I think this change is more benefit than harm. Change-Id: Ib9b4033f3cda273e99c9f0252d0055e203921916 Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2615946 Reviewed-by: Ross McIlroy <rmcilroy@chromium.org> Commit-Queue: Seth Brenith <seth.brenith@microsoft.com> Cr-Commit-Position: refs/heads/master@{#71987} |
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| CODE_OF_CONDUCT.md | ||
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| LICENSE.fdlibm | ||
| LICENSE.strongtalk | ||
| LICENSE.v8 | ||
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| PRESUBMIT.py | ||
| README.md | ||
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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://v8.dev/docs
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 at v8.dev/docs/contribute.