perf(allocator): remove op from StringBuilder::grow_one

[overlookmotel]

Remove a bounds check from StringBuilder::grow_one (which is used by StringBuilder::push_ascii_byte). Rationale is explained in comment added in this PR.

[overlookmotel]

• perf(allocator): remove op from StringBuilder::grow_one #20650 👈 (View in Graphite)
• main

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[codspeed-hq]

Merging this PR will not alter performance

✅ 53 untouched benchmarks
⏩ 3 skipped benchmarks¹

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_{Comparing om/02-20-perf_allocator_remove_op_from_stringbuilder_grow_one_ (b8470d3) with main (399e629)}

Footnotes

1. 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. ↩

[Copilot]

Pull request overview

This PR optimizes oxc_allocator’s StringBuilder growth path by removing a redundant overflow check in StringBuilder::grow_one, which is on the hot path for single-byte pushes (e.g. push_ascii_byte).

Changes:

• Replaced checked_add(...).expect(...) with a direct current_capacity + additional in StringBuilder::grow_one.
• Added an explanatory comment documenting why usize overflow cannot occur for this addition under the existing capacity invariants.

[overlookmotel]

Merge activity

• Mar 23, 9:59 AM UTC: The merge label '0-merge' was detected. This PR will be added to the Graphite merge queue once it meets the requirements.
• Mar 23, 9:59 AM UTC: overlookmotel added this pull request to the Graphite merge queue.
• Mar 23, 10:03 AM UTC: Merged by the Graphite merge queue.