perf(span): add `#[repr(transparent)]` to `Atom` by overlookmotel · Pull Request #16310 · oxc-project/oxc

overlookmotel · 2025-12-01T00:42:21Z

Atom is just a wrapper around a &str, so make it #[repr(transparent)]. This may help perf in some circumstances.

overlookmotel · 2025-12-01T00:42:35Z

perf(span): add #[inline] to Atom methods #16311
perf(span): add #[repr(transparent)] to Atom #16310 👈 (View in Graphite)
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Pull request overview

This PR adds a performance optimization to the Atom<'a> struct by marking it with #[repr(transparent)]. Since Atom is a single-field wrapper around &str, this attribute ensures the compiler treats it identically to &str in terms of memory layout and calling conventions, potentially improving performance in FFI boundaries and function calls. This change aligns with established patterns used throughout the codebase for similar wrapper types like Box, Vec, and other single-field structs in the allocator and traverse modules.

Adds #[repr(transparent)] attribute to Atom<'a> struct
Ensures optimal ABI representation for the single-field wrapper
Maintains consistency with codebase patterns for similar wrapper types

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codspeed-hq · 2025-12-01T00:47:36Z

CodSpeed Performance Report

Merging #16310 will not alter performance

_{Comparing 12-01-perf_span_add_repr_transparent_to_atom_ (9efe73c) with main (43a6c32)}

Summary

✅ 42 untouched
⏩ 3 skipped¹

3 benchmarks were skipped, so the baseline results were used instead. If they were deleted from the codebase, click here and archive them to remove them from the performance reports. ↩

overlookmotel · 2025-12-01T02:29:49Z

Some positive results on benchmarks. Unclear if that's just noise or not. But it certainly won't hurt, so merging.

graphite-app · 2025-12-01T02:30:07Z

Merge activity

Dec 1, 2:30 AM UTC: overlookmotel added this pull request to the Graphite merge queue.
Dec 1, 2:36 AM UTC: Merged by the Graphite merge queue.

`Atom` is just a wrapper around a `&str`, so make it `#[repr(transparent)]`. This *may* help perf in some circumstances.

### 💥 BREAKING CHANGES - 74cf572 ast: [**BREAKING**] Make `source` field of `TSImportType` a `StringLiteral` (#16114) (copilot-swe-agent) - 43156ae ast: [**BREAKING**] Rename `TSImportType` `argument` field to `source` (#16110) (overlookmotel) - 934d873 napi: [**BREAKING**] Drop `armv7-unknown-linux-musleabihf` support (#16105) (Boshen) ### 🚀 Features - 669afe0 ast: Add `Expression::is_jsx` method (#16154) (Dunqing) - 17a8caa parser: Add diagnostic for JSX identifiers with hyphens (#16133) (camchenry) - 0549ae5 parser: Add diagnostic for expected ident after optional chain (#16132) (camchenry) - db839ae parser: Improve diagnostic for unexpected optional declarations (#16131) (camchenry) - bab4bc8 napi/parser: Add type annotations to parse-raw-worker test (#15998) (camc314) ### 🐛 Bug Fixes - 35ed36c traverse: Fix panic when truncating non-ASCII variable names (#16265) (peter) - 9149a26 linter/plugins, napi/parser: Deep freeze visitor keys (#16293) (overlookmotel) - 6b54dab minifier: Incorrect non-null object condition simplification with `&&` and `||` (#16161) (sapphi-red) - 9cc20a1 minifier: Avoid merging side effectful expressions to next assignment statement if the side effect may change the left hand side reference (#16165) (sapphi-red) - 91eb3f2 ast/estree: Convert `TSImportType` `argument` field to `Literal` (#16109) (overlookmotel) - 1199cee parser: Reject invalid modifiers on parameter properties with binding patterns (#16083) (camc314) - f376325 traverse: Remove `console.log` from build script (#16049) (overlookmotel) ### ⚡ Performance - 82d784f lexer: Reduce bounds checks in `Lexer::get_string` (#16317) (overlookmotel) - cc2f352 span: Add `#[inline]` to `Atom` methods (#16311) (overlookmotel) - ffca070 span: Add `#[repr(transparent)]` to `Atom` (#16310) (overlookmotel) - 02bdf90 linter/plugins, napi/parser: Reuse arrays in visitor keys (#16294) (overlookmotel) ### 📚 Documentation - 891e0b4 parser: Add note about falling back to parse TSType in TSImportType (#16119) (camc314) Co-authored-by: Boshen <1430279+Boshen@users.noreply.github.com>

`Atom` is just a wrapper around a `&str`, so make it `#[repr(transparent)]`. This *may* help perf in some circumstances.

### 💥 BREAKING CHANGES - 74cf572 ast: [**BREAKING**] Make `source` field of `TSImportType` a `StringLiteral` (oxc-project#16114) (copilot-swe-agent) - 43156ae ast: [**BREAKING**] Rename `TSImportType` `argument` field to `source` (oxc-project#16110) (overlookmotel) - 934d873 napi: [**BREAKING**] Drop `armv7-unknown-linux-musleabihf` support (oxc-project#16105) (Boshen) ### 🚀 Features - 669afe0 ast: Add `Expression::is_jsx` method (oxc-project#16154) (Dunqing) - 17a8caa parser: Add diagnostic for JSX identifiers with hyphens (oxc-project#16133) (camchenry) - 0549ae5 parser: Add diagnostic for expected ident after optional chain (oxc-project#16132) (camchenry) - db839ae parser: Improve diagnostic for unexpected optional declarations (oxc-project#16131) (camchenry) - bab4bc8 napi/parser: Add type annotations to parse-raw-worker test (oxc-project#15998) (camc314) ### 🐛 Bug Fixes - 35ed36c traverse: Fix panic when truncating non-ASCII variable names (oxc-project#16265) (peter) - 9149a26 linter/plugins, napi/parser: Deep freeze visitor keys (oxc-project#16293) (overlookmotel) - 6b54dab minifier: Incorrect non-null object condition simplification with `&&` and `||` (oxc-project#16161) (sapphi-red) - 9cc20a1 minifier: Avoid merging side effectful expressions to next assignment statement if the side effect may change the left hand side reference (oxc-project#16165) (sapphi-red) - 91eb3f2 ast/estree: Convert `TSImportType` `argument` field to `Literal` (oxc-project#16109) (overlookmotel) - 1199cee parser: Reject invalid modifiers on parameter properties with binding patterns (oxc-project#16083) (camc314) - f376325 traverse: Remove `console.log` from build script (oxc-project#16049) (overlookmotel) ### ⚡ Performance - 82d784f lexer: Reduce bounds checks in `Lexer::get_string` (oxc-project#16317) (overlookmotel) - cc2f352 span: Add `#[inline]` to `Atom` methods (oxc-project#16311) (overlookmotel) - ffca070 span: Add `#[repr(transparent)]` to `Atom` (oxc-project#16310) (overlookmotel) - 02bdf90 linter/plugins, napi/parser: Reuse arrays in visitor keys (oxc-project#16294) (overlookmotel) ### 📚 Documentation - 891e0b4 parser: Add note about falling back to parse TSType in TSImportType (oxc-project#16119) (camc314) Co-authored-by: Boshen <1430279+Boshen@users.noreply.github.com>

github-actions bot added the C-performance Category - Solution not expected to change functional behavior, only performance label Dec 1, 2025

overlookmotel marked this pull request as ready for review December 1, 2025 00:43

Copilot AI review requested due to automatic review settings December 1, 2025 00:43

Copilot started reviewing on behalf of overlookmotel December 1, 2025 00:43 View session

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overlookmotel self-assigned this Dec 1, 2025

overlookmotel mentioned this pull request Dec 1, 2025

perf(span): add #[inline] to Atom methods #16311

Merged

graphite-app bot added the 0-merge Merge with Graphite Merge Queue label Dec 1, 2025

perf(span): add #[repr(transparent)] to Atom (#16310)

ffca070

`Atom` is just a wrapper around a `&str`, so make it `#[repr(transparent)]`. This *may* help perf in some circumstances.

graphite-app bot force-pushed the 12-01-perf_span_add_repr_transparent_to_atom_ branch from 9efe73c to ffca070 Compare December 1, 2025 02:30

graphite-app bot merged commit ffca070 into main Dec 1, 2025
20 checks passed

graphite-app bot deleted the 12-01-perf_span_add_repr_transparent_to_atom_ branch December 1, 2025 02:36

graphite-app bot removed the 0-merge Merge with Graphite Merge Queue label Dec 1, 2025

Boshen mentioned this pull request Dec 1, 2025

release(crates): oxc v0.100.0 #16331

Merged

taearls pushed a commit to taearls/oxc that referenced this pull request Dec 11, 2025

perf(span): add #[repr(transparent)] to Atom (oxc-project#16310)

85ce0b8

`Atom` is just a wrapper around a `&str`, so make it `#[repr(transparent)]`. This *may* help perf in some circumstances.

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perf(span): add `#[repr(transparent)]` to `Atom`#16310

perf(span): add `#[repr(transparent)]` to `Atom`#16310
graphite-app[bot] merged 1 commit intomainfrom
12-01-perf_span_add_repr_transparent_to_atom_

overlookmotel commented Dec 1, 2025 •

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Pull request overview

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codspeed-hq bot commented Dec 1, 2025

CodSpeed Performance Report

Merging #16310 will not alter performance

Summary

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overlookmotel commented Dec 1, 2025 •

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