Add non-`unsafe` `.get_mut()` for `Unsafecell`
- Tracking issue: https://github.com/rust-lang/rust/issues/76943
As discussed in: https://internals.rust-lang.org/t/add-non-unsafe-get-mut-for-unsafecell/12407
- ### [Rendered documentation](https://modest-dubinsky-1f9f47.netlify.app/core/cell/struct.unsafecell)
This PR tries to move the sound `&mut UnsafeCell<T> -> &mut T` projection that all the "downstream" constructions were already relying on, up to the root abstraction, where it rightfully belongs, and officially blessing it.
- this **helps reduce the amount of `unsafe` snippets out there** (_c.f._, the second commit of this PR: 09503fd1b3)
The fact that this getter is now expose for `UnsafeCell<T>` itself, will also help convey the idea that **`UnsafeCell` is not magical _w.r.t._ `&mut` accesses**, contrary to what some people incorrectly think.
- Even the standard library itself at some point had such a confusion, _c.f._ this comment where there is a mention of multi-threaded (and thus _shared_) access despite dealing with exclusive references over unique ownership: 59fb88d061/library/core/src/cell.rs (L498-L499)
r? @RalfJung
Remove DeclareMethods
Most of the `DeclareMethods` API was only used internally by rustc_codegen_llvm. As such, it makes no sense to require other backends to implement them.
(`get_declared_value` and `declare_cfn` were used, in one place, specific to the `main` symbol, which I've replaced with a more specialized function to allow more flexibility in implementation - the intent is that `declare_c_main` can go away once we do something more clever, e.g. @eddyb has ideas around having a MIR shim or somesuch we can explore in a follow-up PR)
Use intra-doc links in core/src/iter when possible
Helps with #75080.
I also updated lots of links to use `fn()` instead of `fn` when possible.
@rustbot modify labels: T-doc A-intra-doc-links
r? @jyn514
Add sample defaults for config.toml
- Allow including defaults in `src/bootstrap/defaults` using `profile = "..."`.
- Add default config files, with a README noting they're experimental and asking you to open an issue if you run into trouble. The config files have comments explaining why the defaults are set.
- Combine config files using the `merge` dependency.
This introduces a new dependency on `merge` that hasn't yet been vetted.
I want to improve the output when `include = "x"` isn't found:
```
thread 'main' panicked at 'fs::read_to_string(&file) failed with No such file or directory (os error 2) ("configuration file did not exist")', src/bootstrap/config.rs:522:28
note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace
failed to run: /home/joshua/rustc/build/bootstrap/debug/bootstrap test tidy
Build completed unsuccessfully in 0:00:00
```
However that seems like it could be fixed in a follow-up.
Closes#76619
Stabilize some Option methods as const
Stabilize the following methods of `Option` as const:
- `is_some`
- `is_none`
- `as_ref`
These methods are currently const under the unstable feature `const_option` (tracking issue: #67441).
I believe these methods to be eligible for stabilization because of the stabilization of #49146 (Allow if and match in constants) and the trivial implementations, see also: [PR#75463](https://github.com/rust-lang/rust/pull/75463).
Related: #76225
Avoid useless sift_down when std::collections::binary_heap::PeekMut is never mutably dereferenced
If `deref_mut` is never called then it's not possible for the element to be mutated without internal mutability, meaning there's no need to call `sift_down`.
This could be a little improvement in cases where you want to mutate the biggest element of the heap only if it satisfies a certain predicate that needs only read access to the element.
Remove MMX from Rust
Follow-up to https://github.com/rust-lang/stdarch/pull/890
This removes most of MMX from Rust (tests pass with small changes), keeping stable `is_x86_feature_detected!("mmx")` working.
De-couple Python and bootstrap slightly
This revises rustbuild's entry points from Python to rely less on magic environment variables, preferring to use Cargo-provided environment variables where feasible.
Notably, BUILD_DIR and BOOTSTRAP_CONFIG are *not* moved, because both more-or-less have some non-trivial discovery logic and replicating it in rustbuild seems unfortunate; if it moved to Cargo that would be a different story.
Best reviewed by-commit.
Stabilize the following methods of `Option` as const:
- `is_some`
- `is_none`
- `as_ref`
Possible because of stabilization of #49146 (Allow if and match in constants).
- Allow including defaults in `src/bootstrap/defaults` using `profile = "..."`
- Add default config files
- Combine config files using the merge dependency.
- Add comments to default config files
- Add a README asking to open an issue if the defaults are bad
- Give a loud error if trying to merge `.target`, since it's not
currently supported
- Use an exhaustive match
- Use `<none>` in config.toml.example to avoid confusion
- Fix bugs in `Merge` derives
Previously, it would completely ignore the profile defaults if there
were any settings in `config.toml`. I sent an email to the `merge` maintainer
asking them to make the behavior in this commit the default.
This introduces a new dependency on `merge` that hasn't yet been vetted.
I want to improve the output when `include = "x"` isn't found:
```
thread 'main' panicked at 'fs::read_to_string(&file) failed with No such file or directory (os error 2) ("configuration file did not exist")', src/bootstrap/config.rs:522:28
note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace
failed to run: /home/joshua/rustc/build/bootstrap/debug/bootstrap test tidy
Build completed unsuccessfully in 0:00:00
```
However that seems like it could be fixed in a follow-up.
This requires that bootstrap is run from the same worktree as the sources it'll
build, but this is basically required for the build to work anyway. You can
still run it from a different directory, just that the files it builds must be
beside it.
This moves build triple discovery for rustbuild from bootstrap.py into a build
script, meaning it will "just work" if building rustbuild via Cargo rather than
Python.
New MIR optimization pass to reduce branches on match of tuples of enums
Fixes#68867 by adding a new pass that turns something like
```rust
let x: Option<()>;
let y: Option<()>;
match (x,y) {
(Some(_), Some(_)) => {0},
_ => {1}
}
```
into something like
```rust
let x: Option<()>;
let y: Option<()>;
let discriminant_x = // get discriminant of x
let discriminant_y = // get discriminant of x
if discriminant_x != discriminant_y {1} else {0}
```
The opt-diffs still have the old basic blocks like
```
bb3: {
_8 = discriminant((*(_4.1: &ViewportPercentageLength))); // scope 0 at $DIR/early-otherwise-branch-68867.rs:21:21: 21:30
switchInt(move _8) -> [1_isize: bb7, otherwise: bb2]; // scope 0 at $DIR/early-otherwise-branch-68867.rs:21:21: 21:30
}
bb4: {
_9 = discriminant((*(_4.1: &ViewportPercentageLength))); // scope 0 at $DIR/early-otherwise-branch-68867.rs:22:23: 22:34
switchInt(move _9) -> [2_isize: bb8, otherwise: bb2]; // scope 0 at $DIR/early-otherwise-branch-68867.rs:22:23: 22:34
}
bb5: {
_10 = discriminant((*(_4.1: &ViewportPercentageLength))); // scope 0 at $DIR/early-otherwise-branch-68867.rs:23:23: 23:34
switchInt(move _10) -> [3_isize: bb9, otherwise: bb2]; // scope 0 at $DIR/early-otherwise-branch-68867.rs:23:23: 23:34
}
```
These do get removed on later passes. I'm not sure if I should include those passes in the test to make it clear?
Rollup of 15 pull requests
Successful merges:
- #76732 (Add docs for `BasicBlock`)
- #76832 (Let backends define custom targets)
- #76866 (Remove unused feature gates from library/ crates)
- #76875 (Move to intra-doc links in library/alloc/src/collections/binary_heap.rs)
- #76876 (Move to intra-doc links in collections/btree/map.rs and collections/linked_list.rs)
- #76877 (Move to intra-doc links in collections/vec_deque.rs and collections/vec_deque/drain.rs)
- #76878 (Move the version number to a plaintext file)
- #76883 (README.md: Remove prompts from code blocks)
- #76887 (Add missing examples on HashSet iter types)
- #76890 (use matches!() macro for simple if let conditions)
- #76891 (don't take `TyCtxt` by reference)
- #76910 (transmute: use diagnostic item)
- #76924 (Add tracking issue for feature(unix_socket_peek))
- #76926 (BTreeMap: code readability tweaks)
- #76940 (Don't allow implementing trait directly on type-alias-impl-trait)
Failed merges:
r? `@ghost`
Don't allow implementing trait directly on type-alias-impl-trait
This is specifically disallowed by the RFC, but we never added a check
for it.
Fixes#76202
transmute: use diagnostic item
closes#66075, we now have no remaining uses of `match_def_path` in the compiler while some uses still remain in `clippy`.
cc @RalfJung
Move the version number to a plaintext file
The Rust version number is currently embedded in bootstrap's source code, which makes it hard to update it automatically or access it outside of ./x.py (as you'd have to parse the source code).
This PR moves the version number to a standalone plaintext file, which makes accessing or updating it trivial.
r? @Mark-Simulacrum
Move to intra-doc links in collections/vec_deque.rs and collections/vec_deque/drain.rs
Helps with #75080.
@rustbot modify labels: T-doc, A-intra-doc-links
Remove unused feature gates from library/ crates
Removes some unused feature gates from library crates. It's likely not a complete list as I only tested a subset for which it's more likely that it is unused.
