update isolate_highest_one for NonZero<T>
## Rationale
Let `x = self` and
`m = (((1 as $Int) << (<$Int>::BITS - 1)).wrapping_shr(self.leading_zeros()))`
Then the previous code computed `NonZero::new_unchecked(x & m)`.
Since `m` has exactly one bit set (the most significant 1-bit of `x`), `(x & m) == m`.
Therefore, the masking step was redundant.
The shift is safe and does not need wrapping because:
* `self.leading_zeros() < $Int::BITS` because `self` is non-zero.
* The result of `unchecked_shr` is non-zero, satisfying the `NonZero` invariant. if wrapping happens we would be violating `NonZero` invariants.
why this micro optimization?
the old code was suboptimal it duplicated `$Int`’s isolate_highest_one logic instead of delegating to it. Since the type already wraps `$Int`, either delegation should be used for clarity or, if keeping a custom implementation, it should be optimized as above.
Add -Zannotate-moves for profiler visibility of move/copy operations (codegen)
**Note:** this is an alternative implementation of https://github.com/rust-lang/rust/pull/147206; rather than being a MIR transform, it adds the annotations closer to codegen. It's functionally the same but the implementation is lower impact and it could be more correct.
---
This implements a new unstable compiler flag `-Zannotate-moves` that makes move and copy operations visible in profilers by creating synthetic debug information. This is achieved with zero runtime cost by manipulating debug info scopes to make moves/copies appear as calls to `compiler_move<T, SIZE>` and `compiler_copy<T, SIZE>` marker functions in profiling tools.
This allows developers to identify expensive move/copy operations in their code using standard profiling tools, without requiring specialized tooling or runtime instrumentation.
The implementation works at codegen time. When processing MIR operands (`Operand::Move` and `Operand::Copy`), the codegen creates an `OperandRef` with an optional `move_annotation` field containing an `Instance` of the appropriate profiling marker function. When storing the operand, `store_with_annotation()` wraps the store operation in a synthetic debug scope that makes it appear inlined from the marker.
Two marker functions (`compiler_move` and `compiler_copy`) are defined in `library/core/src/profiling.rs`. These are never actually called - they exist solely as debug info anchors.
Operations are only annotated if:
- We're generating debug info and the feature is enabled.
- Meets the size threshold (default: 65 bytes, configurable via `-Zannotate-moves=SIZE`), and is non-zero
- Has a memory representation
This has a very small size impact on object file size. With the default limit it's well under 0.1%, and even with a very small limit of 8 bytes it's still ~1.5%. This could be enabled by default.
Sync str::rsplit_once example with str::split_once
This adds `"cfg=".rsplit_once('=')` case to `rsplit_once` example, bringing it in sync with example for `split_once`. For consistency and to make life easier for ones who want to ensure bahaviour of this specific edge case.
style: Use binary literals instead of hex literals in doctests for `highest_one` and `lowest_one`
For example, I think it's easier to understand that the index of the highest bit set to one in `16` is `4` as `0b10000` than as `0x10`.
```rust
assert_eq!(0x10_u64.highest_one(), Some(4));
```
Instead of:
```rust
assert_eq!(0b10000_u64.highest_one(), Some(4));
```
rust-lang/rust#145203
This implements a new unstable compiler flag `-Zannotate-moves` that makes
move and copy operations visible in profilers by creating synthetic debug
information. This is achieved with zero runtime cost by manipulating debug
info scopes to make moves/copies appear as calls to `compiler_move<T, SIZE>`
and `compiler_copy<T, SIZE>` marker functions in profiling tools.
This allows developers to identify expensive move/copy operations in their
code using standard profiling tools, without requiring specialized tooling
or runtime instrumentation.
The implementation works at codegen time. When processing MIR operands
(`Operand::Move` and `Operand::Copy`), the codegen creates an `OperandRef`
with an optional `move_annotation` field containing an `Instance` of the
appropriate profiling marker function. When storing the operand,
`store_with_annotation()` wraps the store operation in a synthetic debug
scope that makes it appear inlined from the marker.
Two marker functions (`compiler_move` and `compiler_copy`) are defined
in `library/core/src/profiling.rs`. These are never actually called -
they exist solely as debug info anchors.
Operations are only annotated if the type:
- Meets the size threshold (default: 65 bytes, configurable via
`-Zannotate-moves=SIZE`)
- Has a non-scalar backend representation (scalars use registers,
not memcpy)
This has a very small size impact on object file size. With the default
limit it's well under 0.1%, and even with a very small limit of 8 bytes
it's still ~1.5%. This could be enabled by default.
add extend_front to VecDeque with specialization like extend
ACP: https://github.com/rust-lang/libs-team/issues/658
Tracking issue: rust-lang/rust#146975
_Text below was written before opening the ACP_
Feature was requested in rust-lang/rust#69939, I recently also needed it so decided to implement it as my first contribution to the Rust standard library. I plan on doing more but wanted to start with a small change.
Some questions I had (both on implementation and design) with answers:
- Q: `extend` allows iterators that yield `&T` where `T` is `Clone`, should extend_front do too?
A: No, users can use [`copied`](https://doc.rust-lang.org/std/iter/trait.Iterator.html#method.copied) and/or [`cloned`](https://doc.rust-lang.org/std/iter/trait.Iterator.html#method.cloned).
- Q: Does this need a whole new trait like Extend or only a method on `VecDeque`?
A: No, see ACP.
- Q: How do I deal with all the code duplication? Most code is similar to that of `extend`, maybe there is a nice way to factor out the code around `push_unchecked`/`push_front_unchecked`.
Will come back to this later.
- Q: Why are certain things behind feature gates, `cfg(not(test))` like `vec::IntoIter` here and `cfg(not(no_global_oom_handling))` like `Vec::extend_from_within`? (I am also looking at implementing `VecDeque::extend_from_within`)
A: See https://github.com/rust-lang/rust/pull/146861#pullrequestreview-3250163369
- Q: Should `extend_front` act like repeated pushes to the front of the queue? This reverses the order of the elements. Doing it different might incur an extra move if the iterator length is not known up front (where do you start placing elements in the buffer?).
A: `extend_front` acts like repeated pushes, `prepend` preserves the element order, see ACP or tracking issue.
Add alignment parameter to `simd_masked_{load,store}`
This PR adds an alignment parameter in `simd_masked_load` and `simd_masked_store`, in the form of a const-generic enum `core::intrinsics::simd::SimdAlign`. This represents the alignment of the `ptr` argument in these intrinsics as follows
- `SimdAlign::Unaligned` - `ptr` is unaligned/1-byte aligned
- `SimdAlign::Element` - `ptr` is aligned to the element type of the SIMD vector (default behavior in the old signature)
- `SimdAlign::Vector` - `ptr` is aligned to the SIMD vector type
The main motive for this is stdarch - most vector loads are either fully aligned (to the vector size) or unaligned (byte-aligned), so the previous signature doesn't cut it.
Now, stdarch will mostly use `SimdAlign::Unaligned` and `SimdAlign::Vector`, whereas portable-simd will use `SimdAlign::Element`.
- [x] `cg_llvm`
- [x] `cg_clif`
- [x] `miri`/`const_eval`
## Alternatives
Using a const-generic/"const" `u32` parameter as alignment (and we error during codegen if this argument is not a power of two). This, although more flexible than this, has a few drawbacks
- If we use an const-generic argument, then portable-simd somehow needs to pass `align_of::<T>()` as the alignment, which isn't possible without GCE
- "const" function parameters are just an ugly hack, and a pain to deal with in non-LLVM backends
We can remedy the problem with the const-generic `u32` parameter by adding a special rule for the element alignment case (e.g. `0` can mean "use the alignment of the element type), but I feel like this is not as expressive as the enum approach, although I am open to suggestions
cc `@workingjubilee` `@RalfJung` `@BoxyUwU`
Stabilize `fmt::from_fn`
Resolvesrust-lang/rust#146705, pending its FCP.
As discussed in that tracking issue and rust-lang/rust#117729, this splits `fmt::from_fn` out from the `debug_closure_helpers` feature.
This PR reverts RUST-147622 for several reasons:
1. The RUST-147622 PR would format the generated core library code using
an arbitrary `rustfmt` picked up from `PATH`, which will cause
hard-to-debug failures when the `rustfmt` used to format the
generated unicode data code versus the `rustfmt` used to format the
in-tree library code.
2. Previously, the `unicode-table-generator` tests were not run under CI
as part of `coretests`, and since for `x86_64-gnu-aux` job we run
library `coretests` with `miri`, the generated tests unfortunately
caused an unacceptably large Merge CI time regression from ~2 hours
to ~3.5 hours, making it the slowest Merge CI job (and thus the new
bottleneck).
3. This PR also has an unintended effect of causing a diagnostic
regression (RUST-148387), though that's mostly an edge case not
properly handled by `rustc` diagnostics.
Given that these are three distinct causes with non-trivial fixes, I'm
proposing to revert this PR to return us to baseline. This is not
prejudice against relanding the changes with these issues addressed, but
to alleviate time pressure to address these non-trivial issues.
stdarch subtree update
Subtree update of `stdarch` to b5c164540c.
Created using https://github.com/rust-lang/josh-sync.
r? `@sayantn`
---
Only the last 2 commits contain manual changes to some incorrect miri tests. The remainder is mechanical, and just synchronizes changes from stdarch.
Make explicit that `TypeId`'s layout and size are unstable
Or worded differently, explicitly remark non-stable-guarantee of `TypeId` layout and size.
This PR makes no *additional* guarantees or non-guarantees, it only emphasizes that `TypeId`'s size and layout are unstable like any other `#[repr(Rust)]` types.
This was discussed during [#t-compiler/meetings > [weekly] 2025-10-30 @ 💬](https://rust-lang.zulipchat.com/#narrow/channel/238009-t-compiler.2Fmeetings/topic/.5Bweekly.5D.202025-10-30/near/547949347), where the compiler team discussed a request https://github.com/rust-lang/rust/pull/148265 to have the standard library (and language) commit to `TypeId` guaranteeing a size upper bound of 16 bytes. In the meeting, the consensus was:
- We were sympathetic to the use case discussed in the request PR, however we feel like this stability guarantee is premature, given that there are unresolved questions surrounding the intended purpose of `TypeId`, and concerns surrounding its collision-resistance properties https://github.com/rust-lang/rust/issues/10389 and https://github.com/rust-lang/rust/issues/129014. We would prefer not making any of such guarantee until the collision-resistance concerns are resolved.
- Committing to a stability guarantee on the size upper bound now would close the door to making `TypeId` larger (even if unlikely for perf reasons).
Given that we have previously broken people who asserted the size of `TypeId` is 8 bytes, it was also discussed in the meeting that we should *explicitly* note that the size and layout of `TypeId` is not a stable guarantee, and is subject to changes between Rust releases, and thus cannot be relied upon -- if breakage in people's code is due to that assumption, it will be considered a won't-fix.
- So even if `#[repr(Rust)]` types have unstable size and layout, this PR makes it explicit for `TypeId` since this type can feel "special" and users can be lead into thinking its size and layout is something they can rely upon.
r? `@scottmcm` (or libs/libs-api/lang)
Rollup of 7 pull requests
Successful merges:
- rust-lang/rust#146573 (Constify Range functions)
- rust-lang/rust#146699 (Add `is_ascii` function optimized for LoongArch64 for [u8])
- rust-lang/rust#148026 (std: don't leak the thread closure if destroying the thread attributes fails)
- rust-lang/rust#148135 (Ignore unix socket related tests for VxWorks)
- rust-lang/rust#148211 (clippy fixes and code simplification)
- rust-lang/rust#148395 (Generalize branch references)
- rust-lang/rust#148405 (Fix suggestion when there were a colon already in generics)
r? `@ghost`
`@rustbot` modify labels: rollup
Generalize branch references
It should be safe to merge this before the rename, and I'd like to do that, so we can test if beta/stable PRs work.
r? ``@marcoieni``
`unicode_data` refactors
Minor refactors to `unicode_data` that occured to me while trying to reduce the size of the tables. Splitting into a separate PR. NFC
Instead of generating a standalone executable to test `unicode_data`,
generate normal tests in `coretests`. This ensures tests are always
generated, and will be run as part of the normal testsuite.
Also change the generated tests to loop over lookup tables, rather than
generating a separate `assert_eq!()` statement for every codepoint. The
old approach produced a massive (20,000 lines plus) file which took
minutes to compile!
To make the final output code easier to see:
* Get rid of the unnecessary line-noise of `.unwrap()`ing calls to
`write!()` by moving the `.unwrap()` into a macro.
* Join consecutive `write!()` calls using a single multiline format
string.
* Replace `.push()` and `.push_str(format!())` with `write!()`.
* If after doing all of the above, there is only a single `write!()`
call in the function, just construct the string directly with
`format!()`.
Remove `#[rustfmt::skip]` from all the generated modules in
`unicode_data.rs`. This means we won't have to worry so much about
getting indetation and formatting right when generating code.
Exempted for now some tables which would be too big when formatted by
`rustfmt`.
Instead of `include_str!()`ing `range_search.rs`, just make it a normal
module under `core::unicode`. This means the same source code doesn't
have to be checked in twice, and it plays nicer with IDEs.
Also rename it to `rt` since it includes functions for searching the
bitsets and case conversion tables as well as the range
represesentation.
Document MaybeUninit bit validity
Partially addresses https://github.com/rust-lang/unsafe-code-guidelines/issues/555 by clarifying that it is sound to write any byte values (initialized or uninitialized) to any `MaybeUninit<T>` regardless of `T`.
r? `@RalfJung`
