6da6e45099
Optimize FastDtoa, in particular Grisu3. In addition to making a microbenchmark, there are a number of smaller and larger changes here: - Replace divisions by power-of-ten with multiplications by their inverses, using an algorithm very similar to the one in libdivide. - For DiyFp::Times(), use 128-bit hardware multiplication if available (which it generally is on 64-bit platforms). - Where possible, send around a pointer to the end of the string, instead of a pointer and a length, reducing register pressure (especially for Intel). Where not (easily) possible, add a local variable to make the compiler understand that length and decimal_point cannot alias. - Change some ints to unsigneds where it helps us avoid sign extensions. - Some minor changes to reduce instruction dependency chains. - Inline BiggestPowerTen(). Actual performance gain is wildly different between platforms. On my 3990X workstation (Zen 2), gains are about 21%. On a M1 Mac Mini, they are about 17%. But on my i7-10610U laptop (Comet Lake, so Skylake microarchitecture), the function is 78% faster. This is probably because large divisions (divisor over 255) seem to hurt a lot on Skylake, but I haven't gone through it in detail. Change-Id: I5b67c257d788a3f7d1be7065d055456852451d68 Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/4110741 Commit-Queue: Steinar H Gunderson <sesse@chromium.org> Reviewed-by: Michael Lippautz <mlippautz@chromium.org> Cr-Commit-Position: refs/heads/main@{#84906} |
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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.