Initial `UnsafePinned` implementation [Part 1: Libs]
Initial libs changes necessary to unblock further work on [RFC 3467](https://rust-lang.github.io/rfcs/3467-unsafe-pinned.html).
Tracking issue: #125735
This PR is split off from #136964, and includes just the libs changes:
- `UnsafePinned` struct
- private `UnsafeUnpin` structural auto trait
- Lang items for both
- Compiler changes necessary to block niches on `UnsafePinned`
This PR does not change codegen, miri, the existing `!Unpin` hack, or anything else. That work is to be split into later PRs.
---
cc ``@RalfJung`` ``@Noratrieb``
``@rustbot`` label F-unsafe_pinned T-libs-api
Move `select_unpredictable` to the `hint` module
There has been considerable discussion in both the ACP (rust-lang/libs-team#468) and tracking issue (#133962) about whether the `bool::select_unpredictable` method should be in `core::hint` instead.
I believe this is the right move for the following reasons:
- The documentation explicitly says that it is a hint, not a codegen guarantee.
- `bool` doesn't have a corresponding `select` method, and I don't think we should be adding one.
- This shouldn't be something that people reach for with auto-completion unless they specifically understand the interactions with branch prediction. Using conditional moves can easily make code *slower* by preventing the CPU from speculating past the condition due to the data dependency.
- Although currently `core::hint` only contains no-ops, this isn't a hard rule (for example `unreachable_unchecked` is a bit of a gray area). The documentation only status that the module contains "hints to compiler that affects how code should be emitted or optimized". This is consistent with what `select_unpredictable` does.
Use `with_native_path` for Windows
Ideally, each platform should use their own native path type internally. This will, for example, allow passing a UTF-16 string directly to `std::fs::File::open` and therefore avoid the need for allocating a new null-terminated wide string. However, doing that for every function and platform all at once makes for a large PR that is way too prone to breaking. So this just does some of the Windows parts.
As with the previous Unix PR (#138832) this is intended to be merely a refactoring so I've avoided anything that may require more substantial changes.
Fix profiler_builtins build script to handle full path to profiler lib
LLVM_PROFILER_RT_LIB may be set to an absolute path (e.g., in Fedora builds), but `-l` expects a library name, not a path. After #138273, this caused builds to fail with a "could not find native static library" error.
This patch updates the build script to split the path into directory and filename, using `cargo::rustc-link-search` for the directory and `cargo::rustc-link-lib=+verbatim` for the file. This allows profiler_builtins to correctly link the static library even when an absolute path is provided.
update ```miniz_oxide``` to 0.8.8
I would normally let the auto actions handle this but it turns out 0.8.7 can trigger a panic when debug assertions are enabled in a few cases so I feel it's important it gets sorted more quickly. (and I would ideally like to yank that version but was worried that could cause some issues had been pulled in as a dependency by this repo already before I discovered the problem)
As it can only happen when debug assertions are enabled (the overflow results in the intended result so it doesn't cause any issue in release mode) and using the wrapping buffer mode when decompressing it is very unlikely to cause any issues here but I would like to get it sorted just to be safe. ```miniz_oxide``` is used in the standard library (and some tools) via ```backtrace-rs ``` which doesn't use a wrapping buffer, and thus won't trigger this condition. There does however seem like there are some tools that do dependency on ```flate2``` which does use ```miniz_oxide``` decompression using a a wrapping buffer and could in theory trigger it if they are run when compiled with debug assertions enabled.
It's kinda unclear what version what tool uses though as several of them specify older versions of flate2 which depended on ```miniz_oxide``` 0.7.x in cargo.toml, and ```miniz_oxide```, and not all have a cargo.lock and due to an older version of ```backtrace``` being in the root Cargo.lock which still depended on ```miniz_oxide``` 0.7.4, so that version is also pulled in alongside the newer version.
libtest: Pass the test's panic payload as Option instead of Result
Passing a `Result<(), &dyn Any>` to `calc_result` requires awkward code at both call sites to build a fake result, for no real benefit. It's much easier to just pass the payload as `Option<&dyn Any>`.
No functional change.
std: Fix build for NuttX targets
Fix std build for all NuttX targets. It is the single largest set of failures on <https://does-it-build.noratrieb.dev/>. Although, ESP-IDF also requires these same gates, there are other issues for those targets.
This can verified be running `x check library/std --target=` for all NuttX targets.
cc ``@no1wudi``
Use the chaining methods on PartialOrd for slices too
#138135 added these doc-hidden trait methods to improve the tuple codegen. This PR adds more implementations and callers so that the codegen for slice (and array) comparisons also improves.
Rollup of 6 pull requests
Successful merges:
- #139107 (std: make `cmath` functions safe)
- #139607 (Add regression test for #127424)
- #139691 (Document that `opt-dist` requires metrics to be enabled)
- #139707 (Fix comment in bootstrap)
- #139708 (Fix name of field in doc comment)
- #139709 (bootstrap: fix typo in doc string)
r? `@ghost`
`@rustbot` modify labels: rollup
std: make `cmath` functions safe
The floating point intrinsics are more difficult, I'll probably wait until #119899 has merged before making them safe as well.
docs: clarify uint exponent for `is_power_of_two`
This makes the documentation more explicit for that method. I know this might seem "nit-picky", but `k` could be interpreted as "any Real or Complex number". A trivial example would be $`3 = 2^{log_2(3)}`$ which "proves that three is a power of two" (according to that vague definition).
BTW, when I read the implementation, I was surprised to see that `1` is considered a power of 2 despite being odd (it does make sense in some contexts, but still not intuitive). So I wrote "positive int" before correcting it to "unsigned int"
Update windows-bindgen to 0.61.0
This updates the automatically generate Windows API bindings. Not much changed this time:
- There's now `Default` implementations for many types, which is convenient. It does however conflict with one place where we implemented a non-zeroed default (to set the length field). But that's no big problem.
- The `--no-core` flag has been renamed to `--no-deps` to more accurately reflect its meaning (i.e. generate all necessary code without requiring additional dependencies).
- The `--link` flag allows us to set the location of the `link!` macro. Currently we use our workspace's `windows_targets` crate but we could move it into library/std using `--link`. However, this would need to be co-ordinated with the `backtrace` crate (which is a separate crate but included in std using `#[path]`). So I've left that for another time.
Post merge analysis / analysis (push) Has been cancelled
Polymorphize `array::IntoIter`'s iterator impl
Today we emit all the iterator methods for every different array width. That's wasteful since the actual array length never even comes into it -- the indices used are from the separate `alive: IndexRange` field, not even the `N` const param.
This PR switches things so that an `array::IntoIter<T, N>` stores a `PolymorphicIter<[MaybeUninit<T>; N]>`, which we *unsize* to `PolymorphicIter<[MaybeUninit<T>]>` and call methods on that non-`Sized` type for all the iterator methods.
That also necessarily makes the layout consistent between the different lengths of arrays, because of the unsizing. Compare that to today <https://rust.godbolt.org/z/Prb4xMPrb>, where different widths can't even be deduped because the offset to the indices is different for different array widths.
LLVM_PROFILER_RT_LIB may be set to an absolute path (e.g., in Fedora builds),
but `-l` expects a library name, not a path. After #138273, this caused builds
to fail with a "could not find native static library" error.
This patch updates the build script to split the path into directory and
filename, using `cargo::rustc-link-search` for the directory and
`cargo::rustc-link-lib=+verbatim` for the file. This allows profiler_builtins to
correctly link the static library even when an absolute path is provided.
add `core::intrinsics::simd::{simd_extract_dyn, simd_insert_dyn}`
fixes https://github.com/rust-lang/rust/issues/137372
adds `core::intrinsics::simd::{simd_extract_dyn, simd_insert_dyn}`, which contrary to their non-dyn counterparts allow a non-const index. Many platforms (but notably not x86_64 or aarch64) have dedicated instructions for this operation, which stdarch can emit with this change.
Future work is to also make the `Index` operation on the `Simd` type emit this operation, but the intrinsic can't be used directly. We'll need some MIR shenanigans for that.
r? `@ghost`
Ensure `swap_nonoverlapping` is really always untyped
This replaces #134954, which was arguably overcomplicated.
## Fixes#134713
Actually using the type passed to `ptr::swap_nonoverlapping` for anything other than its size + align turns out to not work, so this goes back to always erasing the types down to just bytes.
(Except in `const`, which keeps doing the same thing as before to preserve `@RalfJung's` fix from #134689)
## Fixes#134946
I'd previously moved the swapping to use auto-vectorization *on bytes*, but someone pointed out on Discord that the tail loop handling from that left a whole bunch of byte-by-byte swapping around. This goes back to manual tail handling to avoid that, then still triggers auto-vectorization on pointer-width values. (So you'll see `<4 x i64>` on `x86-64-v3` for example.)
Update `u8`-to-and-from-`i8` suggestions.
`u8::cast_signed` and `i8::cast_unsigned` have been stabilised, but `i8::from_ne_bytes` et al. still suggest using `as i8` or `as u8`.
speed up `String::push` and `String::insert`
Addresses the concerns described in #116235.
The performance gain comes mainly from avoiding temporary buffers.
Complex pattern matching in `encode_utf8` (introduced in #67569) has been simplified to a comparison and an exhaustive `match` in the `encode_utf8_raw_unchecked` helper function. It takes a slice of `MaybeUninit<u8>` because otherwise we'd have to construct a normal slice to uninitialized data, which is not desirable, I guess.
Several functions still have that [unneeded zeroing](https://rust.godbolt.org/z/5oKfMPo7j), but a single instruction is not that important, I guess.
`@rustbot` label T-libs C-optimization A-str
Promise `array::from_fn` is generated in order of increasing indices
Fixes#139061
I agree this needs to be documented because of the `FnMut`, either with a guarantee or to explicitly disclaim one.
I'm pretty sure this will be non-controversial (like the other "well sure you *could* do it in a different order, but why?" things were), but I couldn't find any previous libs-api decision on it so it's seemingly a new promise that will need FCP.
Basically, yes, it would be plausible to fill in the reverse order, but there's no obvious way we could ever know that that might even be a good idea, so forward seems like an easy thing to promise. We could always add a `from_fn_rev` or something later if there's ever a strong enough need, but it seems unlikely.
Let's just do the obvious thing so it matches what `[gen(0), gen(1), …, gen(N-1)]` does.
