Branch: refs/heads/main
Home: https://github.com/WebKit/WebKit
Commit: ee4b2082674de598acc8179672ec2d833fdab266
https://github.com/WebKit/WebKit/commit/ee4b2082674de598acc8179672ec2d833fdab266
Author: Sosuke Suzuki <[email protected]>
Date: 2026-08-17 (Mon, 17 Aug 2026)
Changed paths:
A JSTests/stress/generator-and-async-body-without-parameters-hoisting.js
M Source/JavaScriptCore/builtins/BuiltinExecutables.cpp
M Source/JavaScriptCore/bytecode/UnlinkedFunctionExecutable.cpp
M Source/JavaScriptCore/bytecode/UnlinkedFunctionExecutable.h
M Source/JavaScriptCore/bytecompiler/BytecodeGenerator.cpp
M Source/JavaScriptCore/bytecompiler/BytecodeGenerator.h
M Source/JavaScriptCore/runtime/CodeCache.cpp
Log Message:
-----------
[JSC] Do not allocate `UnlinkedFunctionExecutable::RareData` for
generator/async bodies whose wrapper has no parameters
https://bugs.webkit.org/show_bug.cgi?id=321845
Reviewed by Yusuke Suzuki.
When compiling a generator or async function wrapper,
BytecodeGenerator::makeFunction() passes the
wrapper's parameter names to the body's UnlinkedFunctionExecutable so that the
body does not create
locals shadowing them. The names were passed as
std::optional<Vector<Identifier>>, and the optional
was engaged even when the wrapper had no parameters, so the constructor
allocated a 64-byte RareData
just to hold an empty FixedVector. Every executed `async () => { await ... }`,
`async function f() {}` with await, or `function* g() {}` paid for it.
The only consumers call contains() on the list, so an empty list is
indistinguishable from no list.
Pass a plain Vector<Identifier> and only touch RareData when it is non-empty;
the two consumers in
BytecodeGenerator now treat a null list as empty instead of asserting it is
present.
Measured with 100k parameterless async functions each executed once: process
footprint drops by
~6.4 MB (64 bytes per function). No change for bodies whose wrapper has
parameters.
Test: JSTests/stress/generator-and-async-body-without-parameters-hoisting.js
* JSTests/stress/generator-and-async-body-without-parameters-hoisting.js: Added.
(shouldBe):
(generatorNoParams.a):
(generatorNoParams):
(a):
(generatorWithParams):
(async asyncNoParams.a):
(async asyncNoParams):
(async asyncWithParams):
(asyncArrowNoParams.async a):
* Source/JavaScriptCore/builtins/BuiltinExecutables.cpp:
(JSC::BuiltinExecutables::createExecutable):
* Source/JavaScriptCore/bytecode/UnlinkedFunctionExecutable.cpp:
(JSC::UnlinkedFunctionExecutable::UnlinkedFunctionExecutable):
* Source/JavaScriptCore/bytecode/UnlinkedFunctionExecutable.h:
* Source/JavaScriptCore/bytecompiler/BytecodeGenerator.cpp:
(JSC::BytecodeGenerator::BytecodeGenerator):
(JSC::BytecodeGenerator::hoistSloppyModeFunctionIfNecessary):
* Source/JavaScriptCore/bytecompiler/BytecodeGenerator.h:
(JSC::BytecodeGenerator::makeFunction):
* Source/JavaScriptCore/runtime/CodeCache.cpp:
(JSC::CodeCache::getUnlinkedGlobalFunctionExecutable):
Canonical link: https://commits.webkit.org/319283@main
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