refactor(allocator): use latest bumpalo as base for Bump#20963
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Merging this PR will improve performance by 10.09%
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Pull request overview
Refreshes oxc_allocator’s in-repo Bump implementation to closely match the latest upstream bumpalo baseline (including restoring the MIN_ALIGN const parameter), with minimal local adjustments to keep CI green and preserve an auditable divergence trail.
Changes:
- Replace the existing modified
Bumpimplementation with a newer upstream-derived version and reintroduceBump<const MIN_ALIGN: usize = 1>. - Gate public exposure of the
bumpmodule behind atestingfeature so doctests can referenceoxc_allocator::bump::Bumpwithout making it part of the public API in normal builds. - Update allocation tracking snapshot outputs to reflect the allocator behavior changes.
Reviewed changes
Copilot reviewed 6 out of 7 changed files in this pull request and generated 2 comments.
Show a summary per file
| File | Description |
|---|---|
| tasks/track_memory_allocations/allocs_semantic.snap | Updates semantic allocation snapshot values/format after allocator changes. |
| tasks/track_memory_allocations/allocs_minifier.snap | Updates minifier allocation snapshot values/format after allocator changes. |
| crates/oxc_allocator/src/lib.rs | Makes bump private by default; exposes it only under feature = "testing" for doctests/tests. |
| crates/oxc_allocator/src/bumpalo_alloc.rs | Syncs allocator API module with upstream-derived version + lint attribute reshuffling. |
| crates/oxc_allocator/src/bump.rs | Major upstream refresh of Bump, adds MIN_ALIGN const generic, alignment-aware fast path adjustments, and new try_* helpers. |
| crates/oxc_allocator/Cargo.toml | Adds testing feature and self dev-dependency to enable doctests/tests with testing. |
| Cargo.lock | Reflects the new self dev-dependency edge for oxc_allocator. |
This was referenced Apr 2, 2026
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…set` (#20964) 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`.
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Repeat of #18181. #20963 wiped all changes to `bumpalo_alloc.rs`, going back to a fresh copy of `bumpalo`. Re-apply changes from #18181 which were lost in the process - marking error handling functions as `#[cold]`. This PR differs from #18181 in one minor respect. `new_layout_err` is not marked `#[inline(never)]` in this PR. The function is a no-op (unconditionally returns a ZST), so we do want it inlined, but with the`#[cold]`attribute to hint to compiler that it's a cold path.
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Repeat of #18234. #20963 wiped all changes to `bump.rs`, going back to a fresh copy of `bumpalo`. Re-apply changes from #18234 which were lost in the process - increasing default arena chunk size to 16 KiB, and altering `try_with_min_align_and_capacity` to respect the requested capacity in `Bump::with_capacity`. Add a comment to `try_with_min_align_and_capacity` explaining why that change is required.
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#20963 had a test failing on 32-bit platforms. Fix it.
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#18168 copied
bumpalo's code forBumpintooxc_allocatorcrate. #18172, #18181, and #18234 made a few improvements to the implementation.However, #18168 removed various things, and altered others. Notably, it removed the
MIN_ALIGNgeneric param, which we definitely want to keep.I'm going to be working on the allocator, and would like to start with a clean slate, beginning with the "known good" implementation of
bumpalo.This PR removes the previous modified
bumpaloimplementation, and copies latest version ofbumpalofrom main branch into the repo. It then makes the absolute minimum changes necessary just to make CI pass.Note: Unlike #18168, this PR keeps all the doctests for
Bump, using a trick of adding the crate to it's owndev-dependencieswithtestingfeature enabled, and exposingBumponly with that feature.This PR is broken into multiple commits, so we have an exact "trail of breadcrumbs" of how we've diverged from
bumpalo. I intend to manually merge this PR, so that record remains on Github (instead of Graphite squashing all the commits).Later PRs in this stack reapply the changes made in #18172, #18181, and #18234 on top of the fresh base implementation. This PR is a small perf regression, but that will be won back once those other changes are reapplied.