perf(es/parser): Optimize skip_space

[CPunisher]

Description:

1. Originally, the skip space function had two nested loops: the inner loop handled whitespace, and the outer loop checked for slash comments. The inner loop used match to deal with spaces and newlines, and used a jump table when encountering Unicode characters. Now, everything is handled in a single loop, all match statements are removed, and everything goes through the jump table.
2. After finding one space, it’s very likely there are more spaces following. Instead of going back to the jump table each time, it continuously tries to process the spaces in a row.
3. After finding a newline, the lexer's had_line_break is set to true. At this point, it can also skip over any following spaces and newlines continuously, since the had_line_break state only needs to be set once.
4. The original code handled Unicode at the byte level, for example by checking prefixes to determine Unicode length and manually combining multiple bytes into a full UTF-8 character. Now it simply reads the next character directly.

[changeset-bot]

🦋 Changeset detected

Latest commit: 0a74aa1

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[github-actions]

Binary Sizes

File	Size
swc.linux-x64-gnu.node	31M (31909128 bytes)

Commit: 5776883

[codspeed-hq]

CodSpeed Performance Report

Merging #11225 will improve performances by 11.63%

_{Comparing CPunisher:11-03-perf/skip-space (0a74aa1) with main (af134fa)¹}

Summary

⚡ 20 improvements
✅ 118 untouched

Benchmarks breakdown

	Benchmark	BASE	HEAD	Change
⚡	es/codegen/with-parser/large	1.2 ms	1.2 ms	+2.15%
⚡	es/lexer/angular	7.6 ms	7 ms	+7.37%
⚡	es/lexer/backbone	1,022 µs	938.7 µs	+8.88%
⚡	es/lexer/colors	28.8 µs	27.6 µs	+4.36%
⚡	es/lexer/jquery	5.5 ms	5 ms	+9.9%
⚡	es/lexer/jquery mobile	8.5 ms	7.7 ms	+10.27%
⚡	es/lexer/mootools	4.3 ms	3.8 ms	+11.63%
⚡	es/lexer/three	19.7 ms	18.8 ms	+4.51%
⚡	es/lexer/underscore	859.5 µs	791.2 µs	+8.64%
⚡	es/lexer/yui	4.6 ms	4.3 ms	+7.7%
⚡	es/parser/angular	18.7 ms	18.2 ms	+2.8%
⚡	es/parser/backbone	2.9 ms	2.8 ms	+2.99%
⚡	es/parser/cal-com	59.3 ms	57.9 ms	+2.45%
⚡	es/parser/jquery	14.9 ms	14.4 ms	+3.39%
⚡	es/parser/jquery mobile	23.3 ms	22.4 ms	+3.76%
⚡	es/parser/mootools	11.8 ms	11.3 ms	+3.95%
⚡	es/parser/three	71.8 ms	69.2 ms	+3.88%
⚡	es/parser/typescript	399.1 ms	388.5 ms	+2.73%
⚡	es/parser/underscore	2.5 ms	2.4 ms	+2.89%
⚡	es/parser/yui	11.5 ms	11.2 ms	+2.98%

Footnotes

1. No successful run was found on main (2edbd40) during the generation of this report, so af134fa was used instead as the comparison base. There might be some changes unrelated to this pull request in this report. ↩

[Copilot]

Pull Request Overview

This PR refactors the whitespace and comment skipping logic in the ECMAScript lexer by consolidating the implementation into a table-driven approach using byte handlers. The refactoring removes the separate SkipWhitespace struct and moves all whitespace handling directly into the Lexer implementation.

• Introduces helper functions is_irregular_whitespace and is_irregular_line_terminator for Unicode whitespace detection
• Replaces the old skip_space method's generic parameter with a simpler implementation using byte handler lookup table
• Consolidates comment handling directly into the byte handler for / (slash) characters

Reviewed Changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated 2 comments.

File	Description
crates/swc_ecma_parser/src/lexer/whitespace.rs	Major refactoring - removes SkipWhitespace struct, adds Unicode whitespace helper functions, implements new table-driven byte handlers, and moves skip_space method into Lexer impl
crates/swc_ecma_parser/src/lexer/table.rs	Formatting change - adds #[rustfmt::skip] attribute and adjusts comment alignment
crates/swc_ecma_parser/src/lexer/state.rs	Removes generic type parameter from skip_space method calls
crates/swc_ecma_parser/src/lexer/mod.rs	Removes generic type parameter from skip_space method calls and removes the old skip_space implementation

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[kdy1]

Nice improvement! Thanks!

[magic-akari]

Impressive optimization!