perf(semantic): avoid bounds check when checking string literal#17545
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camc314
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December 31, 2025 21:39
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Pull request overview
This PR optimizes the string literal checking code by eliminating an Option wrapper in the hot path when searching for escape sequences. The optimization uses unsafe with proper safety guarantees.
Key changes:
- Introduced a haystack that excludes the last byte (closing quote) to ensure any backslash found has a following byte
- Replaced
.get()withunsafe { get_unchecked() }for performance, eliminating theOptionwrapper - Added
debug_assert!and SAFETY comments to document the invariant
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looks safe enough, and a +1% improvement on the jsx benchmark
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### 🚀 Features - 659c23e linter: Init note field boilerplate (#17589) (Shrey Sudhir) - 6870b64 parser: Add TS1363 error code (#17609) (Sysix) - 23680a3 mangler: Skip mangling only in scopes affected by direct eval (#17612) (camc314) - a7e1643 parser: Add TS2528 error code to duplicate_default_export diagnostic (#17558) (camc314) ### 🐛 Bug Fixes - 1044116 ecmascript: Mark `new Symbol` as non side-effect free (#17568) (camc314) - ab5e4ca isolated-declarations: Strip default values from rest parameter binding patterns (#17602) (camc314) - 68b2e54 minifier: Prevent incorrect ??= transformation when member base is mutated (#17472) (copilot-swe-agent) ### ⚡ Performance - 6067143 semantic: Remove hash when checking identifier (#17564) (camchenry) - a28ab3d semantic: Avoid bounds check when checking string literal (#17545) (camc314) - 04809d1 semantic: Use SIMD for finding backslashes in `check_string_literal` (#17534) (camchenry) - 49ad2f0 semantic: Mark all diagnostic functions as `#[cold]` (#17487) (camc314) - ea82b50 transformer: Mark all diagnostic functions as `#[cold]` (#17486) (camc314) - d968e51 semantic: Mark `checker::check` as `inline(always)` (#17459) (camc314)
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