Branch: refs/heads/main
Home: https://github.com/WebKit/WebKit
Commit: 546d47afe6bf2406ad983b5c35e074b85d1643e1
https://github.com/WebKit/WebKit/commit/546d47afe6bf2406ad983b5c35e074b85d1643e1
Author: Sosuke Suzuki <[email protected]>
Date: 2026-01-08 (Thu, 08 Jan 2026)
Changed paths:
A JSTests/microbenchmarks/array-prototype-flat-depth-1-double.js
A JSTests/microbenchmarks/array-prototype-flat-depth-1-int32.js
A JSTests/microbenchmarks/array-prototype-flat-depth-1-mixed.js
A JSTests/microbenchmarks/array-prototype-flat-depth-1-string.js
A JSTests/microbenchmarks/array-prototype-flat-depth-2.js
A JSTests/microbenchmarks/array-prototype-flat-depth-3.js
A JSTests/microbenchmarks/array-prototype-flat-depth-infinity.js
A JSTests/microbenchmarks/array-prototype-flat-huge-arrays.js
A JSTests/microbenchmarks/array-prototype-flat-large-nested.js
A JSTests/microbenchmarks/array-prototype-flat-small-arrays.js
A JSTests/microbenchmarks/array-prototype-flat-sparse-array.js
A JSTests/stress/array-prototype-flat-hole.js
A JSTests/stress/array-prototype-flat-nested-proxy-array.js
A JSTests/stress/array-prototype-flat-undefined-depth.js
M Source/JavaScriptCore/builtins/ArrayPrototype.js
M Source/JavaScriptCore/runtime/ArrayPrototype.cpp
M Source/JavaScriptCore/runtime/CommonIdentifiers.h
M Source/JavaScriptCore/runtime/JSArray.cpp
M Source/JavaScriptCore/runtime/JSArray.h
Log Message:
-----------
[JSC] Implement `Array.prototype.flat` in C++
https://bugs.webkit.org/show_bug.cgi?id=294503
Reviewed by Yusuke Suzuki.
This patch reverts 300343@main to reland 298127@main.
The only change from the original patch is to treat depthNum
as 1 instead of 0 in patterns like `array.flat(undefined)`.
I confirmed that Google Docs works with this patch on my local
Minibrowser build.
-----
(commit message of the original patch)
This patch implements `Array.prototype.flat` in C++.
The new fast path for `Array#flat` first calculates the length
of the resulting array using O(n) `calculateFlattenedLength`,
then directly sets values into the butterfly buffer of the
resulting array using O(n) `fastFlatIntoBuffer`.
TipOfTree Patched
array-prototype-flat-depth-1-string 474.3101+-47.2922 ^
146.0750+-46.3992 ^ definitely 3.2470x faster
array-prototype-flat-depth-1-double 352.0065+-14.2086 ^
156.4253+-54.2939 ^ definitely 2.2503x faster
array-prototype-flat-large-nested 110.8177+-40.8710 ^
46.0452+-18.8216 ^ definitely 2.4067x faster
array-prototype-flat-huge-arrays 41.7200+-14.7628 ^
20.4875+-5.9254 ^ definitely 2.0364x faster
array-prototype-flat-small-arrays 10.1293+-4.8824 ^
3.8282+-0.4837 ^ definitely 2.6460x faster
array-prototype-flat-depth-infinity 536.4026+-177.3859 ^
222.0425+-35.8608 ^ definitely 2.4158x faster
array-prototype-flat-depth-2 475.2299+-93.6660 ^
179.1500+-63.5912 ^ definitely 2.6527x faster
array-prototype-flat-depth-1-int32 453.2263+-184.5728 ^
154.1721+-56.2397 ^ definitely 2.9397x faster
array-prototype-flat-depth-3 471.8799+-105.4956 ^
151.9625+-72.1298 ^ definitely 3.1052x faster
array-prototype-flat-sparse-array 172.9858+-58.6417 ?
219.7328+-64.4558 ? might be 1.2702x slower
array-prototype-flat-depth-1-mixed 465.5951+-149.2841 ^
177.5621+-96.3248 ^ definitely 2.6222x faster
* JSTests/microbenchmarks/array-prototype-flat-depth-1-double.js: Added.
(shouldBe):
* JSTests/microbenchmarks/array-prototype-flat-depth-1-int32.js: Added.
(shouldBe):
* JSTests/microbenchmarks/array-prototype-flat-depth-1-mixed.js: Added.
(shouldBe):
* JSTests/microbenchmarks/array-prototype-flat-depth-1-string.js: Added.
(shouldBe):
* JSTests/microbenchmarks/array-prototype-flat-depth-2.js: Added.
(shouldBe):
* JSTests/microbenchmarks/array-prototype-flat-depth-3.js: Added.
(shouldBe):
* JSTests/microbenchmarks/array-prototype-flat-depth-infinity.js: Added.
(shouldBe):
* JSTests/microbenchmarks/array-prototype-flat-huge-arrays.js: Added.
(shouldBe):
* JSTests/microbenchmarks/array-prototype-flat-large-nested.js: Added.
(shouldBe):
(createLargeNestedArray):
* JSTests/microbenchmarks/array-prototype-flat-small-arrays.js: Added.
(shouldBe):
* JSTests/microbenchmarks/array-prototype-flat-sparse-array.js: Added.
(shouldBe):
* JSTests/stress/array-prototype-flat-hole.js: Added.
(shouldBe):
* JSTests/stress/array-prototype-flat-nested-proxy-array.js: Added.
(shouldBe):
(const.handler.has):
* JSTests/stress/array-prototype-flat-undefined-depth.js: Added.
(shouldBe):
(shouldBeArray):
* Source/JavaScriptCore/builtins/ArrayPrototype.js:
(flat): Deleted.
* Source/JavaScriptCore/runtime/ArrayPrototype.cpp:
(JSC::ArrayPrototype::finishCreation):
(JSC::flatIntoArray):
(JSC::JSC_DEFINE_HOST_FUNCTION):
* Source/JavaScriptCore/runtime/CommonIdentifiers.h:
* Source/JavaScriptCore/runtime/JSArray.cpp:
(JSC::calculateFlattenedLength):
(JSC::fastFlatIntoBuffer):
(JSC::JSArray::fastFlat):
* Source/JavaScriptCore/runtime/JSArray.h:
Canonical link: https://commits.webkit.org/305324@main
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