This has been verified by kani as a correct optimization
see: https://github.com/rust-lang/rust/issues/110840#issuecomment-1942587398
The new implementation is branchless, and only differs in which NaN
values are produced (if any are produced at all). Which is fine to change.
Aside from NaN handling, this implementation produces bitwise identical
results to the original implementation.
The new implementation is gated on targets that have a fast 64-bit
floating point implementation in hardware, and on WASM.
Unroll first iteration of checked_ilog loop
This follows the optimization of #115913. As shown in https://github.com/rust-lang/rust/pull/115913#issuecomment-2066788006, the performance was improved in all important cases, but some regressions were introduced for the benchmarks `u32_log_random_small`, `u8_log_random` and `u8_log_random_small`.
Basically, #115913 changed the implementation from one division per iteration to one multiplication per iteration plus one division. When there are zero iterations, this is a regression from zero divisions to one division.
This PR avoids this by avoiding the division if we need zero iterations by returning `Some(0)` early. It also reduces the number of multiplications by one in all other cases.
Implement `needs_async_drop` in rustc and optimize async drop glue
This PR expands on #121801 and implements `Ty::needs_async_drop` which works almost exactly the same as `Ty::needs_drop`, which is needed for #123948.
Also made compiler's async drop code to look more like compiler's regular drop code, which enabled me to write an optimization where types which do not use `AsyncDrop` can simply forward async drop glue to `drop_in_place`. This made size of the async block from the [async_drop test](67980dd6fb/tests/ui/async-await/async-drop.rs) to decrease by 12%.
drop_in_place: weaken the claim of equivalence with drop(ptr.read())
The two are *not* semantically equivalent in all cases, so let's not be so definite about this.
Fixes https://github.com/rust-lang/rust/issues/112015
Add lang items for `AsyncFn*`, `Future`, `AsyncFnKindHelper`'s associated types
Adds lang items for `AsyncFnOnce::Output`, `AsyncFnOnce::CallOnceFuture`, `AsyncFnMut::CallRefFuture`, and uses them in the new solver. I'm mostly interested in doing this to help accelerate uplifting the new trait solver into a separate crate.
The old solver is kind of spaghetti, so I haven't moved that to use these lang items (i.e. it still uses `item_name`-based comparisons).
update: Also adds lang items for `Future::Output` and `AsyncFnKindHelper::Upvars`.
cc ``@lcnr``
This is create symmetry between the already existing TAU constant (2pi)
and the newly-introduced FRAC_1_SQRT_2PI, keeping the more common
name while increasing visibility.
rustfmt fixes
The `rmake.rs` entries in `rustfmt.toml` are causing major problems for `x fmt`. This PR removes them and does some minor related cleanups.
r? ``@GuillaumeGomez``
It's reasonable to want to, but in the current implementation this
causes multiple problems.
- All the `rmake.rs` files are formatted every time even when they
haven't changed. This is because they get whitelisted unconditionally
in the `OverrideBuilder`, before the changed files get added.
- The way `OverrideBuilder` works, if any files gets whitelisted then no
unmentioned files will get traversed. This is surprising, and means
that the `rmake.rs` entries broke the use of explicit paths to `x
fmt`, and also broke `GITHUB_ACTIONS=true git check --fmt`.
The commit removes the `rmake.rs` entries, fixes the formatting of a
couple of files that were misformatted (not previously caught due to the
`GITHUB_ACTIONS` breakage), and bans `!`-prefixed entries in
`rustfmt.toml` because they cause all these problems.
update tracking issue for lazy_cell_consume
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Always use the general case char count with `optimize_for_size`
The faster algo is really expensive, over a kilobyte if the full algo is present in a binary.
With this PR the general case algo is picked always instead of only for small strings.
In a test of mine this change makes the total binary go from 3116 bytes to 2032 bytes in opt-level 3 and from 1652 bytes to 1428 bytes in opt-level z. I've seen it much worse in real application, so the savings (especially on 'z') will be higher in many cases.
This is the second pr of this kind after #125606
Stabilize `LazyCell` and `LazyLock`
Closes#109736
This stabilizes the [`LazyLock`](https://doc.rust-lang.org/stable/std/sync/struct.LazyLock.html) and [`LazyCell`](https://doc.rust-lang.org/stable/std/cell/struct.LazyCell.html) types:
```rust
static HASHMAP: LazyLock<HashMap<i32, String>> = LazyLock::new(|| {
println!("initializing");
let mut m = HashMap::new();
m.insert(13, "Spica".to_string());
m.insert(74, "Hoyten".to_string());
m
});
let lazy: LazyCell<i32> = LazyCell::new(|| {
println!("initializing");
92
});
```
r? libs-api
Add assert_unsafe_precondition to unchecked_{add,sub,neg,mul,shl,shr} methods
(Old PR is haunted, opening a new one. See #117494 for previous discussion.)
This ensures that these preconditions are actually checked in debug mode, and hopefully should let people know if they messed up. I've also replaced the calls (I could find) in the code that use these intrinsics directly with those that use these methods, so that the asserts actually apply.
More discussions on people misusing these methods in the tracking issue: https://github.com/rust-lang/rust/issues/85122.
Bump bootstrap compiler to the latest beta compiler
This PR updates the bootstrap compiler, aka stage0 to the latest beta version, since it contains rust-lang/cargo#13925.
It removes those unconditional Cargo warnings:
```
warning: [...]/rust/library/core/Cargo.toml: unused manifest key: lints.rust.unexpected_cfgs.check-cfg
warning: [...]/rust/library/std/Cargo.toml: unused manifest key: lints.rust.unexpected_cfgs.check-cfg
warning: [...]/rust/library/alloc/Cargo.toml: unused manifest key: lints.rust.unexpected_cfgs.check-cfg
```
for all contributors/users of this repository (including CI).
I don't know if that's something we do, or if it's even advisable, feel free to close.
r? `@Mark-Simulacrum`
