fix(allocator): revert changes to get_current_chunk_footer_field_offset

[overlookmotel]

Partial revert of #18168.

#18168 made a small change to get_current_chunk_footer_field_offset (used by Allocator::from_raw_parts).

That change was correct in the context of the other changes made to Bump in that PR, but now that #20963 has rolled back most of those changes, this change needs to be reverted too as it's a potential perf regression with current version of Bump.

[overlookmotel]

• docs(allocator): fix typo in comment #20972 : 2 dependent PRs (#20973 , #20974 )
• docs(allocator): improve doc comment examples for vec2::Vec #20969
• perf(allocator): increase initial chunk size from 512B to 16KB #20968
• perf(allocator): add #[cold] to to error handling functions #20967
• docs(allocator, data_structures): correct comments #20966
• refactor(allocator): remove unnecessary pub(crate) from mod statement #20965
• fix(allocator): revert changes to get_current_chunk_footer_field_offset #20964 👈 (View in Graphite)
• refactor(allocator): use latest bumpalo as base for Bump #20963
• main

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[codspeed-hq]

Merging this PR will not alter performance

✅ 48 untouched benchmarks
⏩ 3 skipped benchmarks¹

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_{Comparing om/04-02-fix_allocator_revert_changes_to_get_current_chunk_footer_field_offset_ (343a594) with main (caa2dce)}

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

Reverts a small internal change to get_current_chunk_footer_field_offset in oxc_allocator, aligning it with the current Bump implementation to avoid a potential performance regression in Allocator::from_raw_parts’s layout-deduction path.

Changes:

• Construct the dummy Bump via Bump::<1>::with_min_align() instead of Bump::new() to keep the offset-deduction code simpler for optimization/const-folding.
• Simplify the raw pointer derivation with ptr::from_ref(&bump) (type inference) while preserving behavior.

[graphite-app]

Merge activity

• Apr 2, 3:08 PM UTC: overlookmotel added this pull request to the Graphite merge queue.
• Apr 2, 3:15 PM UTC: Merged by the Graphite merge queue.