miri: avoid making a full copy of all new allocations #125633
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The Miri subtree was changed cc @rust-lang/miri Some changes occurred to the CTFE / Miri engine cc @rust-lang/miri Some changes occurred to the CTFE / Miri engine cc @rust-lang/miri |
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| // The default implementation does a copy; CTFE machines have a more efficient implementation | ||
| // based on their particular choice for `Provenance`, `AllocExtra`, and `Bytes`. | ||
| let kind = Self::GLOBAL_KIND | ||
| .expect("if GLOBAL_KIND is None, adjust_global_allocation must be overwritten"); |
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🤨 So the implementation that Miri needs is the default, and the const fn interpreter overrides with something simpler? Don't we usually do things the other way around?
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Yeah, but the other way around does not work here and the const-eval interpreter impl is not well-typed in general, in relies on specific choices for the associated type. And meanwhile it seems nice that a default impl is possible.
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I see. It's always ironic when we run into loose typing implementing Rust.
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To me this is actually a sign of a pretty powerful type system -- in the const-eval implementation we of course know more about the concrete choice of types than in the general trait definition, and that lets us safely convert between types that are in general inequal, but are known to be equal in this concrete instance.
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miri: avoid making a full copy of all new allocations Hopefully fixes rust-lang/miri#3637 r? `@saethlin`
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Rollup of 8 pull requests Successful merges: - rust-lang#124251 (Add an intrinsic for `ptr::metadata`) - rust-lang#124320 (Add `--print=check-cfg` to get the expected configs) - rust-lang#125226 (Make more of the test suite run on Mac Catalyst) - rust-lang#125381 (Silence some resolve errors when there have been glob import errors) - rust-lang#125633 (miri: avoid making a full copy of all new allocations) - rust-lang#125638 (Rewrite `lto-smoke`, `simple-rlib` and `mixing-deps` `run-make` tests in `rmake.rs` format) - rust-lang#125639 (Support `./x doc run-make-support --open`) - rust-lang#125664 (Tweak relations to no longer rely on `TypeTrace`) r? `@ghost` `@rustbot` modify labels: rollup
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Rollup of 8 pull requests Successful merges: - rust-lang#124251 (Add an intrinsic for `ptr::metadata`) - rust-lang#124320 (Add `--print=check-cfg` to get the expected configs) - rust-lang#125226 (Make more of the test suite run on Mac Catalyst) - rust-lang#125381 (Silence some resolve errors when there have been glob import errors) - rust-lang#125633 (miri: avoid making a full copy of all new allocations) - rust-lang#125638 (Rewrite `lto-smoke`, `simple-rlib` and `mixing-deps` `run-make` tests in `rmake.rs` format) - rust-lang#125639 (Support `./x doc run-make-support --open`) - rust-lang#125664 (Tweak relations to no longer rely on `TypeTrace`) r? `@ghost` `@rustbot` modify labels: rollup
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Rollup merge of rust-lang#125633 - RalfJung:miri-no-copy, r=saethlin miri: avoid making a full copy of all new allocations Hopefully fixes rust-lang/miri#3637 r? ``@saethlin``
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Add a benchmark for creating large uninit allocations Extracted from #3637 I used this program to confirm that rust-lang/rust#125633 has the desired effect.
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Add a benchmark for creating large uninit allocations Extracted from rust-lang/miri#3637 I used this program to confirm that rust-lang#125633 has the desired effect.
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Hopefully fixes rust-lang/miri#3637
r? @saethlin