perf(semantic): use direct byte access for numeric leading-zero check by camc314 · Pull Request #22642 · oxc-project/oxc

camc314 · 2026-05-21T09:16:44Z

this change avoids loading bytes[1] unless bytes[0] is 0.

Since the common case is that the code is valid (no leading zero), we can skip loading the second byte unless it's actually required.

before:

leading_zero_v1:
        test    rdi, rdi
        sete    al
        cmp     rsi, 2
        setb    cl
        or      cl, al
        je      .LBB0_3
        xor     eax, eax
        ret
.LBB0_3:
        movzx   eax, byte ptr [rdi + 1]
        cmp     byte ptr [rdi], 48
        sete    cl
        add     al, -48
        cmp     al, 10
        setb    al
        and     al, cl
        ret

after:

leading_zero_v2:
        test    rdi, rdi
        setne   al
        cmp     rsi, 2
        setae   cl
        and     cl, al
        cmp     cl, 1
        jne     .LBB1_1
        cmp     byte ptr [rdi], 48
        jne     .LBB1_1
        movzx   eax, byte ptr [rdi + 1]
        add     al, -48
        cmp     al, 10
        setb    al
        ret
.LBB1_1:
        xor     eax, eax
        ret

camc314 · 2026-05-21T09:17:00Z

perf(semantic): use direct byte access for numeric leading-zero check #22642 👈 (View in Graphite)
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codspeed-hq · 2026-05-21T09:24:17Z

Merging this PR will not alter performance

✅ 57 untouched benchmarks
⏩ 3 skipped benchmarks¹

_{Comparing c/05-21-perf_semantic_use_direct_byte_access_for_numeric_leading-zero_check (59c9002) with main (0345a31)}

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. ↩

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Pull request overview

This PR optimizes strict-mode numeric literal validation in oxc_semantic by making the “leading zero followed by digit” check use direct byte indexing, reducing work in the common (non-leading-zero) case.

Changes:

Replaced the bytes() iterator + two next() calls with direct as_bytes() indexing guarded by a length check.
Ensured the second-byte digit check is only evaluated when the first byte is '0' (via short-circuit &&).

Dunqing · 2026-05-21T09:28:05Z

Merge activity

May 21, 9:28 AM UTC: The merge label '0-merge' was detected. This PR will be added to the Graphite merge queue once it meets the requirements.
May 21, 9:28 AM UTC: Dunqing added this pull request to the Graphite merge queue.
May 21, 9:33 AM UTC: Merged by the Graphite merge queue.

…#22642) this change avoids loading `bytes[1]` unless `bytes[0]` is `0`. Since the common case is that the code is valid (no leading zero), we can skip loading the second byte unless it's actually required. before: ``` leading_zero_v1: test rdi, rdi sete al cmp rsi, 2 setb cl or cl, al je .LBB0_3 xor eax, eax ret .LBB0_3: movzx eax, byte ptr [rdi + 1] cmp byte ptr [rdi], 48 sete cl add al, -48 cmp al, 10 setb al and al, cl ret ``` after: ``` leading_zero_v2: test rdi, rdi setne al cmp rsi, 2 setae cl and cl, al cmp cl, 1 jne .LBB1_1 cmp byte ptr [rdi], 48 jne .LBB1_1 movzx eax, byte ptr [rdi + 1] add al, -48 cmp al, 10 setb al ret .LBB1_1: xor eax, eax ret ```

### 🚀 Features - e857b0c napi/minify: Expose legalComments option and result (#20370) (Boshen) - 661132d parser: More friendly error messages for rest assignment target and rest binding element (#22719) (sapphi-red) - ee659b6 transformer/legacy-decorator: Add `strictNullChecks` option for nullable-union design:type (#22266) (Kyle Cannon) ### 🐛 Bug Fixes - e1d064e transformer/class-properties: Reparent lifted private method helpers (#22716) (Cameron) - 4ac0fca minifier: Preserve `0 && (module.exports = { ... })` cjs-module-lexer hint (#22729) (Dunqing) - 40ff611 minifier: Mark peephole loop changed when dropping dead-after-throw statement (#22722) (Dunqing) - 2f7b210 codegen: Emit pife-arrow/function leading comments inside the wrap (#22720) (Dunqing) - e184f74 parser: Improve invalid `import` property access diagnostic (#22693) (camc314) - 7baed9c transformer/private-method: Clear inherited strict flags (#22508) (camc314) - a9ad27e parser: Keep annotation comments leading without preceding newline (#22711) (Dunqing) - 9ea4d64 minifier: Re-evaluate pure/no-side-effects flags after peephole inlining (#22595) (Dunqing) - 07afbb6 minifier: Drop empty-body IIFE wrapper when called with arguments (#22589) (Dunqing) - fa7c463 semantic: Correct TS enum member symbol spans (#22689) (camc314) - 26b9396 semantic: Resolve parameter decorators outside parameter scope (#22623) (camc314) - b284045 parser: Switch to module goal eagerly on `export` (#22684) (Boshen) - dfa931d semantic: Propagate unresolved auto-increment enum value instead of defaulting to 0 (#22646) (Dunqing) - 69a6ba6 transformer/legacy-decorator: Emit Array for ReadonlyArray<T> in decorator metadata (#22265) (Kyle Cannon) - e421ef0 transformer/legacy-decorator: Return runtime binding for design:type (#22640) (Dunqing) - d61e1d7 codegen: Preserve verbatim text of pure/no-side-effects comments (#22525) (Dunqing) - 702b14e minifier: Preserve IIFE structure in DCE-only mode (#22547) (Dunqing) - 917da24 parser: Apply PURE comment through member-access chains (#22566) (Dunqing) - a069b1c codegen: Preserve quotes for cjs-module-lexer equality strings (#22551) (Dunqing) ### ⚡ Performance - 2f623b0 semantic: Skip unresolved checks for re-exports (#22660) (camc314) - 0d9553d semantic: Early-exit `check_object_expression` for objects with <2 properties (#22668) (Dunqing) - d721ad9 semantic: Use direct grandparent lookup for TS type parameters (#22658) (camc314) - 0aff288 semantic: Reorder numeric literal strict mode checks (#22657) (camc314) - 4d5ddb1 semantic: Reorder binding identifier checks (#22656) (camc314) - e32acd8 semantic: Reorder identifier ambient binding check (#22653) (camc314) - 09fe178 semantic: Reorder ident reference strict mode check (#22652) (camc314) - 4b6add2 semantic: Avoid duplicate ident clone for bindings (#22663) (camc314) - 82f9662 parser: Check identifier kind before context flag (#22662) (camc314) - d7cd951 parser: Fast path identifier parsing and inline operator helpers (#22650) (Boshen) - 7b84314 semantic: Use direct byte access for numeric leading-zero check (#22642) (camc314) - 0345a31 semantic: Pre-size class elements hash map (#22618) (camc314) - 04d3065 minifier: Drop per-call buffers in try_fold_concat (#22596) (Dunqing) - 4f289f1 semantic: Resolve_references_for_current_scope without a temp Vec (#22599) (Dunqing) - e862c15 semantic: Avoid heap alloc for var hoist scope ids (#22603) (Dunqing) - 8ff8674 semantic: Early return if `excess` is `0` in `Stats::increase_by` (#22616) (camc314) - 7a4120e semantic: Pre-reserve unresolved_references using Stats::references (#22580) (Dunqing) Co-authored-by: Dunqing <[email protected]>

github-actions Bot added the A-semantic Area - Semantic label May 21, 2026

camc314 marked this pull request as ready for review May 21, 2026 09:23

camc314 requested a review from Dunqing as a code owner May 21, 2026 09:23

Copilot AI review requested due to automatic review settings May 21, 2026 09:23

Copilot started reviewing on behalf of camc314 May 21, 2026 09:23 View session

Copilot AI reviewed May 21, 2026

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Dunqing approved these changes May 21, 2026

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Dunqing added the 0-merge Merge with Graphite Merge Queue label May 21, 2026

graphite-app Bot force-pushed the c/05-21-perf_semantic_use_direct_byte_access_for_numeric_leading-zero_check branch from 59c9002 to 7b84314 Compare May 21, 2026 09:29

graphite-app Bot merged commit 7b84314 into main May 21, 2026
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graphite-app Bot removed the 0-merge Merge with Graphite Merge Queue label May 21, 2026

graphite-app Bot deleted the c/05-21-perf_semantic_use_direct_byte_access_for_numeric_leading-zero_check branch May 21, 2026 09:33

oxc-guard Bot mentioned this pull request May 26, 2026

release(crates): oxc v0.133.0 #22734

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perf(semantic): use direct byte access for numeric leading-zero check#22642

perf(semantic): use direct byte access for numeric leading-zero check#22642
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camc314 commented May 21, 2026 •

edited

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camc314 commented May 21, 2026 • edited Loading Uh oh! There was an error while loading. Please reload this page.

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camc314 commented May 21, 2026

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codspeed-hq Bot commented May 21, 2026

Merging this PR will not alter performance

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camc314 commented May 21, 2026 •

edited

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Dunqing commented May 21, 2026 •

edited by graphite-app Bot

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