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Sync from rust 2025/02/14 #631

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@antoyo antoyo commented Feb 14, 2025

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m-ou-se and others added 30 commits January 7, 2025 16:04
Combined with [1], this will change the overflowing multiplication
operations to return an `extern "C"`-safe type.

Link: rust-lang/compiler-builtins#735 [1]
Make missing_abi lint warn-by-default.

This makes the missing_abi lint warn-by-default, as suggested here: rust-lang/rfcs#3722 (comment)

This needs a lang FCP.
…ntoyo

Use a C-safe return type for `__rust_[ui]128_*` overflowing intrinsics

Combined with [1], this will change the overflowing multiplication operations to return an `extern "C"`-safe type.

Link: rust-lang/compiler-builtins#735 [1]
…tions with dummy spans instead of dropping them entirely

Revert most of #133194 (except the test and the comment fixes). Then refix
not emitting locations at all when the correct location discriminator value
exceeds LLVM's capacity.
remove support for the (unstable) #[start] attribute

As explained by `@Noratrieb:`
`#[start]` should be deleted. It's nothing but an accidentally leaked implementation detail that's a not very useful mix between "portable" entrypoint logic and bad abstraction.

I think the way the stable user-facing entrypoint should work (and works today on stable) is pretty simple:
- `std`-using cross-platform programs should use `fn main()`. the compiler, together with `std`, will then ensure that code ends up at `main` (by having a platform-specific entrypoint that gets directed through `lang_start` in `std` to `main` - but that's just an implementation detail)
- `no_std` platform-specific programs should use `#![no_main]` and define their own platform-specific entrypoint symbol with `#[no_mangle]`, like `main`, `_start`, `WinMain` or `my_embedded_platform_wants_to_start_here`. most of them only support a single platform anyways, and need cfg for the different platform's ways of passing arguments or other things *anyways*

`#[start]` is in a super weird position of being neither of those two. It tries to pretend that it's cross-platform, but its signature is  a total lie. Those arguments are just stubbed out to zero on ~~Windows~~ wasm, for example. It also only handles the platform-specific entrypoints for a few platforms that are supported by `std`, like Windows or Unix-likes. `my_embedded_platform_wants_to_start_here` can't use it, and neither could a libc-less Linux program.
So we have an attribute that only works in some cases anyways, that has a signature that's a total lie (and a signature that, as I might want to add, has changed recently, and that I definitely would not be comfortable giving *any* stability guarantees on), and where there's a pretty easy way to get things working without it in the first place.

Note that this feature has **not** been RFCed in the first place.

*This comment was posted [in May](rust-lang/rust#29633 (comment)) and so far nobody spoke up in that issue with a usecase that would require keeping the attribute.*

Closes rust-lang/rust#29633

try-job: x86_64-gnu-nopt
try-job: x86_64-msvc-1
try-job: x86_64-msvc-2
try-job: test-various
Co-authored-by: Oli Scherer <github35764891676564198441@oli-obk.de>
Separate Builder methods from tcx

As part of the autodiff upstreaming we noticed, that it would be nice to have various builder methods available without the TypeContext, which prevents the normal CodegenCx to be passed around between threads.
We introduce a SimpleCx which just owns the llvm module and llvm context, to encapsulate them.
The previous CodegenCx now implements deref and forwards access to the llvm module or context to it's SimpleCx sub-struct. This gives us a bit more flexibility, because now we can pass (or construct) the SimpleCx in locations where we don't have enough information to construct a CodegenCx, or are not able to pass it around due to the tcx lifetimes (and it not implementing send/sync).

This also introduces an SBuilder, similar to the SimpleCx. The SBuilder uses a SimpleCx, whereas the existing Builder uses the larger CodegenCx. I will push updates to make  implementations generic (where possible) to be implemented once and work for either of the two. I'll also clean up the leftover code.

`call` is a bit tricky, because it requires a tcx, I probably need to duplicate it after all.

Tracking:

- rust-lang/rust#124509
This has been unstably const since [1], but a tracking issue was never
created. Per discussion on Zulip [2], there should not be any blockers
to making this const-stable. The function does not provide any
functionality at compile time but does allow code reuse between const-
and non-const functions, so stabilize it here.

[1]: rust-lang/rust#92226
[2]: https://rust-lang.zulipchat.com/#narrow/channel/146212-t-compiler.2Fconst-eval/topic/const_black_box
Stabilize `const_black_box`

This has been unstably const since #92226, but a tracking issue was never created. Per [discussion on Zulip][zulip], there should not be any blockers to making this const-stable. The function does not provide any functionality at compile time but does allow code reuse between const- and non-const functions, so stabilize it here.

[zulip]: https://rust-lang.zulipchat.com/#narrow/channel/146212-t-compiler.2Fconst-eval/topic/const_black_box
Rollup of 8 pull requests

Successful merges:

 - #135414 (Stabilize `const_black_box`)
 - #136150 (ci: use windows 2025 for i686-mingw)
 - #136258 (rustdoc: rename `issue-\d+.rs` tests to have meaningful names (part 11))
 - #136270 (Remove `NamedVarMap`.)
 - #136278 (add constraint graph to polonius MIR dump)
 - #136287 (LLVM changed the nocapture attribute to captures(none))
 - #136291 (some test suite cleanups)
 - #136296 (float::min/max: mention the non-determinism around signed 0)

r? `@ghost`
`@rustbot` modify labels: rollup
tree-wide: parallel: Fully removed all `Lrc`, replaced with `Arc`

tree-wide: parallel: Fully removed all `Lrc`, replaced with `Arc`

This is continuation of rust-lang/rust#132282 .

I'm pretty sure I did everything right. In particular, I searched all occurrences of `Lrc` in submodules and made sure that they don't need replacement.

There are other possibilities, through.

We can define `enum Lrc<T> { Rc(Rc<T>), Arc(Arc<T>) }`. Or we can make `Lrc` a union and on every clone we can read from special thread-local variable. Or we can add a generic parameter to `Lrc` and, yes, this parameter will be everywhere across all codebase.

So, if you think we should take some alternative approach, then don't merge this PR. But if it is decided to stick with `Arc`, then, please, merge.

cc "Parallel Rustc Front-end" ( rust-lang/rust#113349 )

r? SparrowLii

`@rustbot` label WG-compiler-parallel
This is the same as Linkage::Internal except that it doesn't emit any
symbol. Some backends may not support it and it isn't all that useful
anyway.
It can only be used for certain LLVM internal variables like
llvm.global_ctors which users are not allowed to define.
… r=compiler-errors

compiler: mostly-finish `rustc_abi` updates

This almost-finishes all the updates in the compiler to use `rustc_abi` and removes some of the reexports of `rustc_abi` items in `rustc_target` that were previously available.

r? ```@compiler-errors```
Update bootstrap compiler and rustfmt

The rustfmt version we previously used formats things differently from what the latest nightly rustfmt does. This causes issues for subtrees that get formatted both in-tree and in their own repo. Updating the rustfmt used in-tree solves those issues. Also bumped the bootstrap compiler as the stage0 update command always updates both at the same
time.
jhpratt and others added 13 commits February 13, 2025 03:53
…4, r=SparrowLii

Parallel-compiler-related cleanup

Parallel-compiler-related cleanup

I carefully split changes into commits. Commit messages are self-explanatory. Squashing is not recommended.

cc "Parallel Rustc Front-end" rust-lang/rust#113349

r? SparrowLii

``@rustbot`` label: +WG-compiler-parallel
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