The majority of char case replacements are single char replacements,
so storing them as [char; 3] wastes a lot of space.
This commit splits the replacement tables for both `to_lower` and
`to_upper` into two separate tables, one with single-character mappings
and one with multi-character mappings.
This reduces the binary size for programs using all of these tables
with roughly 24K bytes.
Since ascii chars are already handled by a special case in the
`to_lower` and `to_upper` functions, there's no need to waste space on
them in the LUTs.
Ensure `ptr::read` gets all the same LLVM `load` metadata that dereferencing does
I was looking into `array::IntoIter` optimization, and noticed that it wasn't annotating the loads with `noundef` for simple things like `array::IntoIter<i32, N>`. Trying to narrow it down, it seems that was because `MaybeUninit::assume_init_read` isn't marking the load as initialized (<https://rust.godbolt.org/z/Mxd8TPTnv>), which is unfortunate since that's basically its reason to exist.
The root cause is that `ptr::read` is currently implemented via the *untyped* `copy_nonoverlapping`, and thus the `load` doesn't get any type-aware metadata: no `noundef`, no `!range`. This PR solves that by lowering `ptr::read(p)` to `copy *p` in MIR, for which the backends already do the right thing.
Fortuitiously, this also improves the IR we give to LLVM for things like `mem::replace`, and fixes a couple of long-standing bugs where `ptr::read` on `Copy` types was worse than `*`ing them.
Zulip conversation: <https://rust-lang.zulipchat.com/#narrow/stream/219381-t-libs/topic/Move.20array.3A.3AIntoIter.20to.20ManuallyDrop/near/341189936>
cc `@erikdesjardins` `@JakobDegen` `@workingjubilee` `@the8472`
Fixes#106369Fixes#73258
Remove `identity_future` indirection
This was previously needed because the indirection used to hide some unexplained lifetime errors, which it turned out were related to the `min_choice` algorithm.
Removing the indirection also solves a couple of cycle errors, large moves and makes async blocks support the `#[track_caller]`annotation.
Fixes https://github.com/rust-lang/rust/issues/104826.
Stabilize `atomic_as_ptr`
Fixes#66893
This stabilizes the `as_ptr` methods for atomics. The stabilization feature gate used here is `atomic_as_ptr` which supersedes `atomic_mut_ptr` to match the change in https://github.com/rust-lang/rust/pull/107736.
This needs FCP.
New stable API:
```rust
impl AtomicBool {
pub const fn as_ptr(&self) -> *mut bool;
}
impl AtomicI32 {
pub const fn as_ptr(&self) -> *mut i32;
}
// Includes all other atomic types
impl<T> AtomicPtr<T> {
pub const fn as_ptr(&self) -> *mut *mut T;
}
```
r? libs-api
``@rustbot`` label +needs-fcp
I keep forgetting that rust calls this `and_then` and trying to search for `flatmap`.
`and_then`'s docs even mention "Some languages call this operation flatmap",
but it doesn't show up as a result in the search at `https://doc.rust-lang.org/std/?search=flatmap`
Move `Option::as_slice` to an always-sound implementation
This approach depends on CSE to not have any branches or selects when the guessed offset is correct -- which it always will be right now -- but to also be *sound* (just less efficient) if the layout algorithms change such that the guess is incorrect.
The codegen test confirms that CSE handles this as expected, leaving the optimal codegen.
cc JakobDegen #108545
This approach depends on CSE to not have any branches or selects when the guessed offset is correct -- which it always will be right now -- but to also be *sound* (just less efficient) if the layout algorithms change such that the guess is incorrect.
I was looking into `array::IntoIter` optimization, and noticed that it wasn't annotating the loads with `noundef` for simple things like `array::IntoIter<i32, N>`.
Turned out to be a more general problem as `MaybeUninit::assume_init_read` isn't marking the load as initialized (<https://rust.godbolt.org/z/Mxd8TPTnv>), which is unfortunate since that's basically its reason to exist.
This PR lowers `ptr::read(p)` to `copy *p` in MIR, which fortuitiously also improves the IR we give to LLVM for things like `mem::replace`.
Stabilize `nonzero_min_max`
## Overall
Stabilizes `nonzero_min_max` to allow the "infallible" construction of ordinary minimum and maximum `NonZero*` instances.
The feature is fairly straightforward and already matured for some time in stable toolchains.
```rust
let _ = NonZeroU8::MIN;
let _ = NonZeroI32::MAX;
```
## History
* On 2022-01-25, implementation was [created](https://github.com/rust-lang/rust/pull/93293).
## Considerations
* This report is fruit of the inanition observed after two unsuccessful attempts at getting feedback.
* Other constant variants discussed at https://github.com/rust-lang/rust/issues/89065#issuecomment-923238190 are orthogonal to this feature.
Fixes https://github.com/rust-lang/rust/issues/89065
Fix the docs for pointer method with_metadata_of
The name of the argument to `{*const T, *mut T}::with_metadata_of` was changed from `val` to `meta` recently, but the docs weren't updated to match.
Relevant pull request: #103701
Rollup of 8 pull requests
Successful merges:
- #108754 (Retry `pred_known_to_hold_modulo_regions` with fulfillment if ambiguous)
- #108759 (1.41.1 supported 32-bit Apple targets)
- #108839 (Canonicalize root var when making response from new solver)
- #108856 (Remove DropAndReplace terminator)
- #108882 (Tweak E0740)
- #108898 (Set `LIBC_CHECK_CFG=1` when building Rust code in bootstrap)
- #108911 (Improve rustdoc-gui/tester.js code a bit)
- #108916 (Remove an unused return value in `rustc_hir_typeck`)
Failed merges:
r? `@ghost`
`@rustbot` modify labels: rollup
Guide `panic_immediate_abort` users away from `-Cpanic=unwind` and
towards `-Cpanic=abort` to avoid an accidental use of the feature with
the unwind strategy, e.g., on a targets where unwind is the default.
The `-Cpanic=unwind` combination doesn't offer the same benefits, since
the code would still be generated under the assumption that functions
implemented in Rust can unwind.
This was previously needed because the indirection used to hide some unexplained lifetime errors, which it turned out were related to the `min_choice` algorithm.
Removing the indirection also solves a couple of cycle errors, large moves and makes async blocks support the `#[track_caller]` annotation.
Use `nuw` when calculating slice lengths from `Range`s
An `assume` would definitely not be worth it, but since the flag is almost free we might as well tell LLVM this, especially on `_unchecked` calls where there's no obvious way for it to deduce it.
(Today neither safe nor unsafe indexing gets it: <https://rust.godbolt.org/z/G1jYT548s>)
Add `round_ties_even` to `f32` and `f64`
Tracking issue: #96710
Redux of #82273. See also #55107
Adds a new method, `round_ties_even`, to `f32` and `f64`, that rounds the float to the nearest integer , rounding halfway cases to the number with an even least significant bit. Uses the `roundeven` LLVM intrinsic to do this.
Of the five IEEE 754 rounding modes, this is the only one that doesn't already have a round-to-integer function exposed by Rust (others are `round`, `floor`, `ceil`, and `trunc`). Ties-to-even is also the rounding mode used for int-to-float and float-to-float `as` casts, as well as float arithmentic operations. So not having an explicit rounding method for it seems like an oversight.
Bikeshed: this PR currently uses `round_ties_even` for the name of the method. But maybe `round_ties_to_even` is better, or `round_even`, or `round_to_even`?
An `assume` would definitely not be worth it, but since the flag is almost free we might as well tell LLVM this, especially on `_unchecked` calls where there's no obvious way for it to deduce it.
(Today neither safe nor unsafe indexing gets it: <https://rust.godbolt.org/z/G1jYT548s>)
Use `partial_cmp` to implement tuple `lt`/`le`/`ge`/`gt`
In today's implementation, `(A, B)::gt` contains calls to *both* `A::eq` *and* `A::gt`.
That's fine for primitives, but for things like `String`s it's kinda weird -- `(String, usize)::gt` has a call to both `bcmp` and `memcmp` (<https://rust.godbolt.org/z/7jbbPMesf>) because when `bcmp` says the `String`s aren't equal, it turns around and calls `memcmp` to find out which one's bigger.
This PR changes the implementation to instead implement `(A, …, C, Z)::gt` using `A::partial_cmp`, `…::partial_cmp`, `C::partial_cmp`, and `Z::gt`. (And analogously for `lt`, `le`, and `ge`.) That way expensive comparisons don't need to be repeated.
Technically this is an observable change on stable, so I've marked it `needs-fcp` + `T-libs-api` and will
r? rust-lang/libs-api
I'm hoping that this will be non-controversial, however, since it's very similar to the observable changes that were made to the derives (#81384#98655) -- like those, this only changes behaviour if a type overrode behaviour in a way inconsistent with the rules for the various traits involved.
(The first commit here is #108156, adding the codegen test, which I used to make sure this doesn't regress behaviour for primitives.)
Zulip conversation about this change: <https://rust-lang.zulipchat.com/#narrow/stream/219381-t-libs/topic/.60.3E.60.20on.20Tuples/near/328392927>.
Match unmatched backticks in library/
Found with GNU grep:
```
grep -rEn '^(([^`]*`){2})*[^`]*`[^`]*$' library/ | rg -v '\s*[//]?.{1,2}```'
```
split out from #108685 as per advice.
Add `Atomic*::from_ptr`
This PR adds functions in the following form to all atomic types:
```rust
impl AtomicT {
pub const unsafe fn from_ptr<'a>(ptr: *mut T) -> &'a AtomicT;
}
```
r? `@m-ou-se` (we've talked about it before)
I'm not sure about docs & safety requirements, I'd appreciate some feedback on them.
