Avoid Vec allocation in TyCtxt::mk_place_elem#155778
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kevinheavey wants to merge 1 commit intorust-lang:mainfrom
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Avoid Vec allocation in TyCtxt::mk_place_elem#155778kevinheavey wants to merge 1 commit intorust-lang:mainfrom
kevinheavey wants to merge 1 commit intorust-lang:mainfrom
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`mk_place_elem` appends a single `PlaceElem` to an existing (interned) projection. The current implementation copies the projection into a fresh `Vec`, pushes the new element, and re-interns the slice, which allocates on the heap on every call. Feed the elements through `mk_place_elems_from_iter` so that `CollectAndApply`'s hand-unrolled stack fast path (up to 9 elements, in `rustc_type_ir::interner`) kicks in for the common case of short projections and the `Vec` allocation is skipped entirely. The behavior is identical for longer projections (the fast path falls back to a `Vec` internally).
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r? @JohnTitor rustbot has assigned @JohnTitor. Use Why was this reviewer chosen?The reviewer was selected based on:
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Seems reasonable, let's see what perf says. @bors try @rust-timer queue |
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Awaiting bors try build completion. @rustbot label: +S-waiting-on-perf |
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⌛ Trying commit 5cd9d92 with merge 7a0916d… To cancel the try build, run the command Workflow: https://github.com/rust-lang/rust/actions/runs/24960896151 |
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…c, r=<try> Avoid Vec allocation in TyCtxt::mk_place_elem
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mk_place_elemappends a singlePlaceElemto an existing (interned) projection. The current implementation copies the projection into a freshVec, pushes the new element, and re-interns the slice, which allocates on every call.Feed the elements through
mk_place_elems_from_iterso thatCollectAndApply's hand-unrolled stack fast path (up to 9 elements, inrustc_type_ir::interner) kicks in for the common case of short projections and theVecallocation is skipped entirely. The behavior is identical for longer projections (the fast path falls back to aVecinternally).