chore: improve performance of DOM traversal operations #12863
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🦋 Changeset detectedLatest commit: 39acd8d The changes in this PR will be included in the next version bump. This PR includes changesets to release 1 package
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Rich-Harris
reviewed
Aug 15, 2024
Rich-Harris
reviewed
Aug 15, 2024
| @@ -116,7 +116,7 @@ export function each(node, flags, get_collection, get_key, render_fn, fallback_f | |||
| var parent_node = /** @type {Element} */ (node); | |||
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| anchor = hydrating | |||
| ? set_hydrate_node(/** @type {Comment | Text} */ (parent_node.firstChild)) | |||
| ? set_hydrate_node(/** @type {Comment | Text} */ (get_first_child(parent_node))) | |||
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In #12863 (comment) I was referring to these calls too. Isn't parent_node.firstChild preferable? Surely get_first_child is polymorphic (megamorphic?), given we call it with different node types
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All the IC call-sites that use these functions come back as inlined so they're not really in the JIT code.
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Interestingly, we used to have this optimisation but we removed them as we thought they didn't improve performance. It turns out that we were wrong and they actually do and it was likely that Chrome 125 was had a regression. Specifically we can avoid a nasty V8 deopt on one of the most expensive hot paths in the codebase.
Megamorphic deopt
Monomorphic, no deopts