Use NonNull in slice::Iter and slice::IterMut.
`ptr` of `slice::Iter` and `slice::IterMut` can never be null, but this
fact wasn't exploited for layout optimizations. By changing `ptr` from
`*<mutability> T` to `NonNull<T>`, the compiler can now optimize layout
of `Option<Iter<'a, T>>`.
Closes#67228
Implement padding for IpAddr without heap alloc
Implements padding for `IpAddr`s without heap allocations.
This fixes issue #66810 .
cc @jethrogb @mzohreva
Add LLVM `skip-rebuild` option to `x.py`
This PR reimplements parts of @Walther's work from #65848, and closes#65612.
I decided not to implement the [arguments to override this setting](https://github.com/rust-lang/rust/issues/65612#issuecomment-544247546) in this PR. If there's strong feeling that this change shouldn't be merged without the overrides then I'm happy to close this until I've had a chance to add them in. Otherwise I'll aim to submit a second PR with those this weekend.
I'd have liked to have tested the change in `native.rs`, but there didn't seem to be any existing test infrastructure. I ran this a few times manually and it _worked on my machine_ though... 😬
Various const eval and pattern matching ICE fixes
r? @RalfJung
cc @spastorino
This PR does not change existing behaviour anymore and just fixes a bunch of ICEs reachable from user code (sometimes even on stable via obscure union transmutes).
`ptr` of `slice::Iter` and `slice::IterMut` can never be null, but this
fact wasn't exploited for layout optimizations. By changing `ptr` from
`*<mutability> T` to `NonNull<T>`, the compiler can now optimize layout
of `Option<Iter<'a, T>>`.
Prepare for lowering or-patterns
This is probably best reviewed commit-by-commit.
* Rustfmt `rustc_mir::build::{self, matches}`
* Remove `-Znll-dont-emit-read-for-match`
* Split `match_expr` into smaller functions
* Feature gate or-patterns in const contexts
cc https://github.com/rust-lang/rust/issues/54883
r? @Centril
