bors 5423745db8 Auto merge of #105871 - llogiq:option-as-slice, r=scottmcm ... Add `Option::as_`(`mut_`)`slice` This adds the following functions: * `Option<T>::as_slice(&self) -> &[T]` * `Option<T>::as_mut_slice(&mut self) -> &[T]` The `as_slice` and `as_mut_slice_mut` functions benefit from an optimization that makes them completely branch-free. ~~Unfortunately, this optimization is not available on by-value Options, therefore the `into_slice` implementations use the plain `match` + `slice::from_ref` approach.~~ Note that the optimization's soundness hinges on the fact that either the niche optimization makes the offset of the `Some(_)` contents zero or the mempory layout of `Option<T>` is equal to that of `Option<MaybeUninit<T>>`. The idea has been discussed on [Zulip](https://rust-lang.zulipchat.com/#narrow/stream/219381-t-libs/topic/Option.3A.3Aas_slice). Notably the idea for the `as_slice_mut` and `into_slice´ methods came from `@cuviper` and `@Sp00ph` hardened the optimization against niche-optimized Options. The [rust playground](https://play.rust-lang.org/?version=nightly&mode=release&edition=2021&gist=74f8e4239a19f454c183aaf7b4a969e0) shows that the generated assembly of the optimized method is basically only a copy while the naive method generates code containing a `test dx, dx` on x86_64. --- EDIT from reviewer: ACP is https://github.com/rust-lang/libs-team/issues/150		2023-03-01 12:32:57 +00:00
..
benches	Shrink size of array benchmarks	2023-02-14 05:01:24 +00:00
primitive_docs	Add primitive documentation to libcore	2021-09-12 02:23:08 +00:00
src	Auto merge of #105871 - llogiq:option-as-slice, r=scottmcm	2023-03-01 12:32:57 +00:00
tests	add missing feature in core/tests	2023-02-28 10:07:57 +01:00
Cargo.toml	Update rand in the stdlib tests, and remove the getrandom feature from it	2023-01-04 14:52:41 -08:00