Branch: refs/heads/main
Home: https://github.com/WebKit/WebKit
Commit: bde9f45eabd5205808b2ae36791b669bdd4fe61a
https://github.com/WebKit/WebKit/commit/bde9f45eabd5205808b2ae36791b669bdd4fe61a
Author: Yusuke Suzuki <[email protected]>
Date: 2025-11-12 (Wed, 12 Nov 2025)
Changed paths:
M Source/JavaScriptCore/dfg/DFGByteCodeParser.cpp
M Source/JavaScriptCore/dfg/DFGOperations.cpp
M Source/JavaScriptCore/inspector/JSInjectedScriptHost.cpp
M Source/JavaScriptCore/runtime/JSMapIterator.cpp
M Source/JavaScriptCore/runtime/JSMapIterator.h
M Source/JavaScriptCore/runtime/JSSetIterator.cpp
M Source/JavaScriptCore/runtime/JSSetIterator.h
M Source/JavaScriptCore/runtime/MapPrototype.cpp
M Source/JavaScriptCore/runtime/OrderedHashTable.h
M Source/JavaScriptCore/runtime/OrderedHashTableHelper.h
M Source/JavaScriptCore/runtime/SetPrototype.cpp
M Source/WebCore/bindings/js/SerializedScriptValue.cpp
Log Message:
-----------
[JSC] Optimize Map / Set iteration
https://bugs.webkit.org/show_bug.cgi?id=302382
rdar://164537076
Reviewed by Sosuke Suzuki.
This patch improves two things in Map / Set iterations.
1. OrderedHashTable should not load used capacity information. It turned
out this unnecessary load is causing a bit of cache stall (according
to the profiler data). Since entries are always ending with JSEmpty
keys (we are extending hash table before reaching to full entries.
Thus it is guaranteed that these entries are having unused slots at
the end.
2. JSMapIterator and JSSetIterator are always materializing Storage of
Map / Set even for empty Map and Set. But this is not great since
it can throw an error in the constructor of JSSetIterator /
JSMapIterator. Also this unnecessarily allocates memory for empty Map
and Set. Instead, JSSetIterator / JSMapIterator's next operations
should handle initial state of JSMapIterator and JSSetIterator
appropriately. If they are having empty storage, and iterated object
is having empty storage too, then it means that both are empty and we
finished the iteration. If iterated object is having a storage, then
we can grab it and start iterating. This avoids many unnecessary
allocations when Map / Set are empty.
* Source/JavaScriptCore/dfg/DFGByteCodeParser.cpp:
(JSC::DFG::ByteCodeParser::handleIntrinsicCall):
* Source/JavaScriptCore/dfg/DFGOperations.cpp:
(JSC::DFG::JSC_DEFINE_JIT_OPERATION):
* Source/JavaScriptCore/inspector/JSInjectedScriptHost.cpp:
(Inspector::cloneMapIteratorObject):
(Inspector::cloneSetIteratorObject):
* Source/JavaScriptCore/runtime/JSMapIterator.cpp:
(JSC::JSMapIterator::finishCreation):
(JSC::JSC_DEFINE_HOST_FUNCTION):
* Source/JavaScriptCore/runtime/JSMapIterator.h:
* Source/JavaScriptCore/runtime/JSSetIterator.cpp:
(JSC::JSSetIterator::finishCreation):
(JSC::JSC_DEFINE_HOST_FUNCTION):
* Source/JavaScriptCore/runtime/JSSetIterator.h:
* Source/JavaScriptCore/runtime/MapPrototype.cpp:
(JSC::createMapIteratorObject):
* Source/JavaScriptCore/runtime/OrderedHashTable.h:
(JSC::OrderedHashTable::storage):
* Source/JavaScriptCore/runtime/OrderedHashTableHelper.h:
(JSC::OrderedHashTableHelper::copyImpl):
(JSC::OrderedHashTableHelper::transitAndNext):
* Source/JavaScriptCore/runtime/SetPrototype.cpp:
(JSC::createSetIteratorObject):
* Source/WebCore/bindings/js/SerializedScriptValue.cpp:
(WebCore::CloneSerializer::serialize):
Canonical link: https://commits.webkit.org/302900@main
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