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2023-04-16ci: add a runner for vanilla LLVM 16Josh Stone-0/+2
Like #107044, this will let us track compatibility with LLVM 16 going forward, especially after we eventually upgrade our own to the next. This also drops `tidy` here and in `x86_64-gnu-llvm-15`, syncing with that change in #106085.
2023-03-11Move `Option::as_slice` to an always-sound implementationScott McMurray-5/+13
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.
2023-03-01Add `Option::as_slice`(`_mut`)Andre Bogus-0/+28
This adds the following functions: * `Option<T>::as_slice(&self) -> &[T]` * `Option<T>::as_slice_mut(&mut self) -> &[T]` The `as_slice` and `as_slice_mut` functions benefit from an optimization that makes them completely branch-free. 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>>`.