Andreas Kling 3c3e591f03 LibWeb: Add a fast (iterative) selector matcher for trivial selectors ...

If we determine that a selector is simple enough, we now run it using a
special matching loop that traverses up the DOM ancestor chain without
recursion.

The criteria for this fast path are:

- All combinators involved must be either descendant or child.
- Only tag name, class, ID and attribute selectors allowed.

It's definitely possible to increase the coverage of this fast path,
but this first version already provides a substantial reduction in time
spent evaluating selectors.

48% of the selectors evaluated when loading our GitHub repo are now
using this fast path.

18% speed-up on the "Descendant and child combinators" subtest of
StyleBench. :^)

2024-03-19 16:48:22 +01:00

7.4 KiB

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