perf(parser): faster checking for invalid modifiers by overlookmotel · Pull Request #15717 · oxc-project/oxc

overlookmotel · 2025-11-15T13:25:46Z

Modifiers contains 2 different representations of the modifiers list:

ModifierFlags bitflags
Vec<Modifier>

When checking modifiers, use ModifierFlags (which is really cheap), rather than iterating through the Vec<Modifier> (more expensive).

Only if the first check fails, then loop through the Vec to get the spans of the invalid modifiers, and generate diagnostics.

Because invalid modifiers are rare, move the logic for looping through the Vec into a #[cold] #[inline(never)] function. This should make it possible to inline verify_modifiers into all the call sites.

Produces a small perf improvement on parser benchmarks (+0.1% - +0.2%).

overlookmotel · 2025-11-15T13:26:00Z

perf(parser): faster checking for invalid modifiers #15717 👈 (View in Graphite)
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codspeed-hq · 2025-11-15T13:31:08Z

CodSpeed Performance Report

Merging #15717 will not alter performance

_{Comparing 11-15-perf_parser_faster_checking_for_invalid_modifiers (624bb75) with main (d8d4e31)¹}

Summary

✅ 37 untouched

No successful run was found on main (4608549) during the generation of this report, so d8d4e31 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 optimizes the modifier checking logic in the parser by using bitflag operations instead of iterating through vectors. The key performance improvement comes from checking ModifierFlags (bitflags) first, and only looping through the Vec<Modifier> to get spans for diagnostics when invalid modifiers are detected.

Key changes:

Added contains_all_flags method to check multiple flags efficiently
Refactored verify_modifiers to use bitflag intersection check before iterating modifiers
Moved error reporting logic into a #[cold] #[inline(never)] function to enable better inlining of the main verification function

Reviewed Changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated no comments.

File	Description
crates/oxc_parser/src/modifiers.rs	Added `contains_all_flags` method and refactored `verify_modifiers` to check bitflags first, with cold error reporting path
crates/oxc_parser/src/js/class.rs	Updated all `verify_modifiers` call sites to use bitflag negation syntax and adapted to new diagnostic function signatures
crates/oxc_parser/src/ts/types.rs	Replaced manual loop with `verify_modifiers` call using bitflag negation
crates/oxc_parser/src/diagnostics.rs	Updated `modifiers_cannot_appear_here` signature to match standard modifier diagnostic pattern

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Boshen · 2025-11-16T03:03:25Z

Merge activity

Nov 16, 3:03 AM UTC: The merge label '0-merge' was detected. This PR will be added to the Graphite merge queue once it meets the requirements.
Nov 16, 3:03 AM UTC: Boshen added this pull request to the Graphite merge queue.
Nov 16, 3:14 AM UTC: Merged by the Graphite merge queue.

`Modifiers` contains 2 different representations of the modifiers list: * `ModifierFlags` bitflags * `Vec<Modifier>` When checking modifiers, use `ModifierFlags` (which is really cheap), rather than iterating through the `Vec<Modifier>` (more expensive). Only if the first check fails, then loop through the `Vec` to get the spans of the invalid modifiers, and generate diagnostics. Because invalid modifiers are rare, move the logic for looping through the `Vec` into a `#[cold]` `#[inline(never)]` function. This should make it possible to inline `verify_modifiers` into all the call sites. Produces a small perf improvement on parser benchmarks (+0.1% - +0.2%).

### 💥 BREAKING CHANGES - ea51b0b napi: [**BREAKING**] Standardize function naming with sync suffixes (#15661) (Boshen) ### 🚀 Features - 77efb76 parser: Improve error message for invalid switch clauses (#15728) (sapphi-red) - 5691727 parser: Improve `import source` `from` error message (#15727) (sapphi-red) - b7404bc parser: Improve error message for missing function body (#15726) (sapphi-red) - 71c2fb0 parser: Improve error message when JSX is found while not enabled (#15725) (sapphi-red) - 56e7e44 minifier: Disable removal of unnecessary `use strict` directives for DCE (#15691) (sapphi-red) - 8a61cfd allocator, ast: Introduce `UnstableAddress` trait (#15700) (overlookmotel) - f5ce55a napi: Export all options using wildcard exports (Boshen) - 68703b9 minifier: Rotate binary expressions to remove parentheses (#15473) (sapphi-red) ### 🐛 Bug Fixes - c023ba6 semantic: Do not duplicate statements in temp `Vec` when binding `TSModuleDeclaration`s (#15724) (overlookmotel) - d60ca81 parser: Reject `import something 'source'` (#15746) (sapphi-red) - e0728fa ast: Exclude comment end position from `is_inside_comment` check (#15753) (camc314) - 9f54a36 semantic: Error on `\00` in strict mode (#15743) (sapphi-red) - 440a977 ast: Include rest properties when using `get_binding_identifiers` (#15710) (camc314) ### ⚡ Performance - 1f09d3c parser: Faster checking for invalid modifiers (#15717) (overlookmotel) - d8d4e31 ast: Use loop instead of recursion in `TSModuleDeclarationBody::as_module_block_mut` (#15713) (overlookmotel) ### 📚 Documentation - e033d50 ast: Clarify behavior of `TSModuleDeclaration::has_use_strict_directive` (#15730) (overlookmotel) - 9eda70f allocator: Improve docs for `Address` methods (#15697) (overlookmotel)

`Modifiers` contains 2 different representations of the modifiers list: * `ModifierFlags` bitflags * `Vec<Modifier>` When checking modifiers, use `ModifierFlags` (which is really cheap), rather than iterating through the `Vec<Modifier>` (more expensive). Only if the first check fails, then loop through the `Vec` to get the spans of the invalid modifiers, and generate diagnostics. Because invalid modifiers are rare, move the logic for looping through the `Vec` into a `#[cold]` `#[inline(never)]` function. This should make it possible to inline `verify_modifiers` into all the call sites. Produces a small perf improvement on parser benchmarks (+0.1% - +0.2%).

### 💥 BREAKING CHANGES - ea51b0b napi: [**BREAKING**] Standardize function naming with sync suffixes (oxc-project#15661) (Boshen) ### 🚀 Features - 77efb76 parser: Improve error message for invalid switch clauses (oxc-project#15728) (sapphi-red) - 5691727 parser: Improve `import source` `from` error message (oxc-project#15727) (sapphi-red) - b7404bc parser: Improve error message for missing function body (oxc-project#15726) (sapphi-red) - 71c2fb0 parser: Improve error message when JSX is found while not enabled (oxc-project#15725) (sapphi-red) - 56e7e44 minifier: Disable removal of unnecessary `use strict` directives for DCE (oxc-project#15691) (sapphi-red) - 8a61cfd allocator, ast: Introduce `UnstableAddress` trait (oxc-project#15700) (overlookmotel) - f5ce55a napi: Export all options using wildcard exports (Boshen) - 68703b9 minifier: Rotate binary expressions to remove parentheses (oxc-project#15473) (sapphi-red) ### 🐛 Bug Fixes - c023ba6 semantic: Do not duplicate statements in temp `Vec` when binding `TSModuleDeclaration`s (oxc-project#15724) (overlookmotel) - d60ca81 parser: Reject `import something 'source'` (oxc-project#15746) (sapphi-red) - e0728fa ast: Exclude comment end position from `is_inside_comment` check (oxc-project#15753) (camc314) - 9f54a36 semantic: Error on `\00` in strict mode (oxc-project#15743) (sapphi-red) - 440a977 ast: Include rest properties when using `get_binding_identifiers` (oxc-project#15710) (camc314) ### ⚡ Performance - 1f09d3c parser: Faster checking for invalid modifiers (oxc-project#15717) (overlookmotel) - d8d4e31 ast: Use loop instead of recursion in `TSModuleDeclarationBody::as_module_block_mut` (oxc-project#15713) (overlookmotel) ### 📚 Documentation - e033d50 ast: Clarify behavior of `TSModuleDeclaration::has_use_strict_directive` (oxc-project#15730) (overlookmotel) - 9eda70f allocator: Improve docs for `Address` methods (oxc-project#15697) (overlookmotel)

github-actions bot added A-parser Area - Parser C-performance Category - Solution not expected to change functional behavior, only performance labels Nov 15, 2025

overlookmotel force-pushed the 11-15-perf_parser_faster_checking_for_invalid_modifiers branch 2 times, most recently from 17bfdde to 624bb75 Compare November 15, 2025 15:12

overlookmotel marked this pull request as ready for review November 15, 2025 15:12

Copilot AI review requested due to automatic review settings November 15, 2025 15:12

Copilot started reviewing on behalf of overlookmotel November 15, 2025 15:13 View session

Copilot finished reviewing on behalf of overlookmotel November 15, 2025 15:16

Copilot AI reviewed Nov 15, 2025

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overlookmotel requested a review from Boshen November 15, 2025 16:51

overlookmotel assigned Boshen Nov 15, 2025

Boshen added the 0-merge Merge with Graphite Merge Queue label Nov 16, 2025

graphite-app bot force-pushed the 11-15-perf_parser_faster_checking_for_invalid_modifiers branch from 624bb75 to 1f09d3c Compare November 16, 2025 03:06

graphite-app bot merged commit 1f09d3c into main Nov 16, 2025
21 checks passed

graphite-app bot deleted the 11-15-perf_parser_faster_checking_for_invalid_modifiers branch November 16, 2025 03:14

graphite-app bot removed the 0-merge Merge with Graphite Merge Queue label Nov 16, 2025

Boshen mentioned this pull request Nov 17, 2025

release(crates): oxc v0.98.0 #15771

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perf(parser): faster checking for invalid modifiers#15717

perf(parser): faster checking for invalid modifiers#15717
graphite-app[bot] merged 1 commit intomainfrom
11-15-perf_parser_faster_checking_for_invalid_modifiers

overlookmotel commented Nov 15, 2025 •

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CodSpeed Performance Report

Merging #15717 will not alter performance

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