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LibWeb: Don't create mutation record node lists if nobody is interested

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By deferring allocation of StaticNodeList objects until we know somebody
actually wants the MutationRecord, we avoid a *lot* of allocation work.

This shaves several seconds off of loading https://tc39.es/ecma262/

At least one other engine (WebKit) skips creating mutation records if
nobody is interested, so even if this is observable somehow, we would
at least match the behavior of a major engine.
This commit is contained in:
Andreas Kling 2023-05-17 19:47:16 +02:00
parent 0f2b6345c6
commit 80d6330a26
4 changed files with 22 additions and 31 deletions
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4
Userland/Libraries/LibWeb/DOM/CharacterData.cpp
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@ -71,9 +71,7 @@ WebIDL::ExceptionOr<void> CharacterData::replace_data(size_t offset, size_t coun
count = length - offset;
// 4. Queue a mutation record of "characterData" for node with null, null, node’s data, « », « », null, and null.
auto added_node_list = TRY(StaticNodeList::create(realm(), {}));
auto removed_node_list = TRY(StaticNodeList::create(realm(), {}));
queue_mutation_record(MutationType::characterData, {}, {}, m_data, added_node_list, removed_node_list, nullptr, nullptr);
queue_mutation_record(MutationType::characterData, {}, {}, m_data, {}, {}, nullptr, nullptr);
// 5. Insert data into node’s data after offset code units.
// 6. Let delete offset be offset + data’s length.