add a csky-unknown-linux-gnuabiv2 target

This is the rustc side changes to support csky based Linux target(`csky-unknown-linux-gnuabiv2`).

Tier 3 policy:

> A tier 3 target must have a designated developer or developers (the "target maintainers") on record to be CCed when issues arise regarding the target. (The mechanism to track and CC such developers may evolve over time.)

I pledge to do my best maintaining it.

> Targets must use naming consistent with any existing targets; for instance, a target for the same CPU or OS as an existing Rust target should use the same name for that CPU or OS. Targets should normally use the same names and naming conventions as used elsewhere in the broader ecosystem beyond Rust (such as in other toolchains), unless they have a very good reason to diverge. Changing the name of a target can be highly disruptive, especially once the target reaches a higher tier, so getting the name right is important even for a tier 3 target.

This `csky`  section is the arch name and the `unknown-linux` section is the same as other linux target, and `gnuabiv2` is from the  cross-compile toolchain of  `gcc`

> Target names should not introduce undue confusion or ambiguity unless absolutely necessary to maintain ecosystem compatibility. For example, if the name of the target makes people extremely likely to form incorrect beliefs about what it targets, the name should be changed or augmented to disambiguate it.

I think the explanation in platform support doc is enough to make this aspect clear.

> Tier 3 targets may have unusual requirements to build or use, but must not create legal issues or impose onerous legal terms for the Rust project or for Rust developers or users.

It's using open source tools only.

> The target must not introduce license incompatibilities.

No new license

> Anything added to the Rust repository must be under the standard Rust license (MIT OR Apache-2.0).

Understood.

> The target must not cause the Rust tools or libraries built for any other host (even when supporting cross-compilation to the target) to depend on any new dependency less permissive than the Rust licensing policy. This applies whether the dependency is a Rust crate that would require adding new license exceptions (as specified by the tidy tool in the rust-lang/rust repository), or whether the dependency is a native library or binary. In other words, the introduction of the target must not cause a user installing or running a version of Rust or the Rust tools to be subject to any new license requirements.

There are no new dependencies/features required.

> Compiling, linking, and emitting functional binaries, libraries, or other code for the target (whether hosted on the target itself or cross-compiling from another target) must not depend on proprietary (non-FOSS) libraries. Host tools built for the target itself may depend on the ordinary runtime libraries supplied by the platform and commonly used by other applications built for the target, but those libraries must not be required for code generation for the target; cross-compilation to the target must not require such libraries at all. For instance, rustc built for the target may depend on a common proprietary C runtime library or console output library, but must not depend on a proprietary code generation library or code optimization library. Rust's license permits such combinations, but the Rust project has no interest in maintaining such combinations within the scope of Rust itself, even at tier 3.

As previously said it's using open source tools only.

> "onerous" here is an intentionally subjective term. At a minimum, "onerous" legal/licensing terms include but are not limited to: non-disclosure requirements, non-compete requirements, contributor license agreements (CLAs) or equivalent, "non-commercial"/"research-only"/etc terms, requirements conditional on the employer or employment of any particular Rust developers, revocable terms, any requirements that create liability for the Rust project or its developers or users, or any requirements that adversely affect the livelihood or prospects of the Rust project or its developers or users.

There are no such terms present/

> Neither this policy nor any decisions made regarding targets shall create any binding agreement or estoppel by any party. If any member of an approving Rust team serves as one of the maintainers of a target, or has any legal or employment requirement (explicit or implicit) that might affect their decisions regarding a target, they must recuse themselves from any approval decisions regarding the target's tier status, though they may otherwise participate in discussions.

I'm not the reviewer here.

> This requirement does not prevent part or all of this policy from being cited in an explicit contract or work agreement (e.g. to implement or maintain support for a target). This requirement exists to ensure that a developer or team responsible for reviewing and approving a target does not face any legal threats or obligations that would prevent them from freely exercising their judgment in such approval, even if such judgment involves subjective matters or goes beyond the letter of these requirements.

I'm not the reviewer here.

> Tier 3 targets should attempt to implement as much of the standard libraries as possible and appropriate (core for most targets, alloc for targets that can support dynamic memory allocation, std for targets with an operating system or equivalent layer of system-provided functionality), but may leave some code unimplemented (either unavailable or stubbed out as appropriate), whether because the target makes it impossible to implement or challenging to implement. The authors of pull requests are not obligated to avoid calling any portions of the standard library on the basis of a tier 3 target not implementing those portions.

It supports for std

> The target must provide documentation for the Rust community explaining how to build for the target, using cross-compilation if possible. If the target supports running binaries, or running tests (even if they do not pass), the documentation must explain how to run such binaries or tests for the target, using emulation if possible or dedicated hardware if necessary.

I have added the documentation, and I think it's clear.

> Tier 3 targets must not impose burden on the authors of pull requests, or other developers in the community, to maintain the target. In particular, do not post comments (automated or manual) on a PR that derail or suggest a block on the PR based on a tier 3 target. Do not send automated messages or notifications (via any medium, including via `@)` to a PR author or others involved with a PR regarding a tier 3 target, unless they have opted into such messages.

Understood.

> Backlinks such as those generated by the issue/PR tracker when linking to an issue or PR are not considered a violation of this policy, within reason. However, such messages (even on a separate repository) must not generate notifications to anyone involved with a PR who has not requested such notifications.

Understood.

> Patches adding or updating tier 3 targets must not break any existing tier 2 or tier 1 target, and must not knowingly break another tier 3 target without approval of either the compiler team or the maintainers of the other tier 3 target.

I believe I didn't break any other target.

> In particular, this may come up when working on closely related targets, such as variations of the same architecture with different features. Avoid introducing unconditional uses of features that another variation of the target may not have; use conditional compilation or runtime detection, as appropriate, to let each target run code supported by that target.

I think there are no such problems in this PR.

Rollup of 5 pull requests

Successful merges:

 - #114745 (Make Const more useful in smir)
 - #114752 (fixed *const [type error] does not implement the Copy trait)
 - #114760 (DebugInfo: Updates test cases that add method declarations.)
 - #114815 (Update books)
 - #114817 (Remove unnecessary FIXME)

r? `@ghost`
`@rustbot` modify labels: rollup

Remove unnecessary FIXME

Found this while browsing rustc, I traced it back to https://github.com/rust-lang/rust/pull/27893 when MIR first introduced, some time passed since then and I think this FIXME is no longer necessary.

Update books

## rust-lang/book

3 commits in 668c64760b5c7ea654facb4ba5fe9faddfda27cc..72187f5cd0beaaa9c6f584156bcd88f921871e83
2023-08-04 14:42:07 UTC to 2023-08-03 13:36:44 UTC

- redirects: change link for the `#![no_std]` tutorial (rust-lang/book#3705)
- [chpt10.2] - Small wording changes (rust-lang/book#3724)
- Improve sentence (rust-lang/book#3725)

## rust-embedded/book

1 commits in 1e5556dd1b864109985d5871616ae6b9164bcead..99ad2847b865e96d8ae7b333d3ee96963557e621
2023-08-11 06:31:04 UTC to 2023-08-11 06:31:04 UTC

- Fix a small typo in qemu.md (rust-embedded/book#359)

## rust-lang/nomicon

1 commits in 302b995bcb24b70fd883980fd174738c3a10b705..388750b081c0893c275044d37203f97709e058ba
2023-08-10 21:15:21 UTC to 2023-08-10 21:15:21 UTC

- Document thiscall abi (rust-lang/nomicon#311)

## rust-lang/reference

10 commits in 1ea0178266b3f3f613b0fabdaf16a83961c99cdb..d43038932adeb16ada80e206d4c073d851298101
2023-08-12 19:07:28 UTC to 2023-07-16 20:12:46 UTC

- Document thiscall abi (rust-lang/reference#1092)
- add section about implied bounds (rust-lang/reference#1261)
- Clearly specify the `instruction_set` effects (rust-lang/reference#1307)
- Fix merge queue building twice. (rust-lang/reference#1383)
- Clarify UB around immutability & mutation (rust-lang/reference#1385)
- mention the extra const UB (rust-lang/reference#1273)
- Operator expressions: make the note about division by zero clearer. (rust-lang/reference#1384)
- Make unsafe keyword docs less confusing (rust-lang/reference#1379)
- Say that division by zero for primitive types panics (rust-lang/reference#1382)
- Add CI trigger for merge queues. (rust-lang/reference#1381)

## rust-lang/rust-by-example

3 commits in 8a87926a985ce32ca1fad1be4008ee161a0b91eb..07e0df2f006e59d171c6bf3cafa9d61dbeb520d8
2023-07-24 11:37:55 UTC to 2023-07-24 11:35:36 UTC

- Added attribute unused_labels - fixed warning. (rust-lang/rust-by-example#1729)
- more explanation about panic (rust-lang/rust-by-example#1728)
- chore: add the portuguese version of this project to `readme.md` (rust-lang/rust-by-example#1727)

## rust-lang/rustc-dev-guide

31 commits in b5a12d95e32ae53791cc6ab44417774667ed2ac6..b123ab4754127d822ffb38349ce0fbf561f1b2fd
2023-08-14 08:34:59 UTC to 2023-07-11 06:02:34 UTC

- fix: stabilize debugger_visualizer (rust-lang/rustc-dev-guide#1766)
- feat(part-5-intro): make "Part 5" obvious (rust-lang/rustc-dev-guide#1753)
- Update from `#[warn_]` to `#[warning]` diagnostic attributes (rust-lang/rustc-dev-guide#1765)
- Add RPITIT documentation (rust-lang/rustc-dev-guide#1764)
- fix(visitor.md): fix a type name in a code sample (rust-lang/rustc-dev-guide#1762)
- fix(name-resolution): remove unnecessary closing paranthesis (rust-lang/rustc-dev-guide#1760)
- fix(macro-expansion.md): fix the article `an` to `a` (rust-lang/rustc-dev-guide#1759)
- fix(serialization.md): fix the name of a derive macro (rust-lang/rustc-dev-guide#1756)
- fix(serialization.md): add a necessary plural suffix (rust-lang/rustc-dev-guide#1757)
- fix(salsa.md): add punctuation to prevent confusion (rust-lang/rustc-dev-guide#1754)
- fix(salsa.md): remove duplicate "To Be" verb (rust-lang/rustc-dev-guide#1755)
- feat(fuzzing.md): make `halfempty` word a link (rust-lang/rustc-dev-guide#1750)
- fix(about.md): use `a` instead of `an` (rust-lang/rustc-dev-guide#1751)
- refactor(git.md): make git-scm links clickable (rust-lang/rustc-dev-guide#1747)
- fix(walkthrough.md) add a comma operator to eliminate ambiguity (rust-lang/rustc-dev-guide#1749)
- fix(git.md): remove a confusing end of sentence character (rust-lang/rustc-dev-guide#1748)
- refactor(profiling/with_perf): remove a wrong to be verb (rust-lang/rustc-dev-guide#1746)
- refactor(tests/headers): remove duplicate list item (rust-lang/rustc-dev-guide#1745)
- refactor(test/headers.md): make the meaning more obvious (rust-lang/rustc-dev-guide#1744)
- refactor(tests/ui): remove unnecessary duplicate word (rust-lang/rustc-dev-guide#1743)
- refactor(compiletest): remove unnecessary duplicate word (rust-lang/rustc-dev-guide#1742)
- generic_arguments.md: substs -> GenericArgs (rust-lang/rustc-dev-guide#1741)
- fix(suggested): remove an unnecessary and confusing statement (rust-lang/rustc-dev-guide#1739)
- fix(how-to-build-and-run): fix a typo ("fromer" -> "former") (rust-lang/rustc-dev-guide#1736)
- fix(how-to-build-and-run): remove a wrong paragraph (rust-lang/rustc-dev-guide#1735)
- coverage code has moved (rust-lang/rustc-dev-guide#1728)
- linked issue is closed (rust-lang/rustc-dev-guide#1729)
- remove duplicate reference in about-this-guide.md (rust-lang/rustc-dev-guide#1734)
- Explain more in depth what early and late bound generic parameters are (rust-lang/rustc-dev-guide#1732)
- add section for normalization with the new solver (rust-lang/rustc-dev-guide#1731)
- Improve cleanup-crew.md with an example post (rust-lang/rustc-dev-guide#1730)

DebugInfo: Updates test cases that add method declarations.

We've investigated one reason why debugging information often goes wrong at https://reviews.llvm.org/D152095.
> LLVM can't handle IR where subprogram definitions are nested within DICompositeType when doing LTO builds, because there's no good way to cross the CU boundary to insert a nested DISubprogram definition in one CU into a type defined in another CU.

In #111167, we added a declaration for the DISubprogram for the method. This PR completes this test case.

stream history: https://rust-lang.zulipchat.com/#narrow/stream/187780-t-compiler.2Fwg-llvm/topic/Dwarf.20CUs/near/384269475.

fixed *const [type error] does not implement the Copy trait

Removes "error: arguments for inline assembly must be copyable" when moving an unknown type

Fixes: #113788

Make Const more useful in smir

Since https://github.com/rust-lang/rust/pull/114587 is merged, we can make use of what we built and make Const more useful by making it not `Opaque`

r? `@spastorino`

core/any: remove Provider trait, rename Demand to Request

This touches on two WIP features:

* `error_generic_member_access`
  * tracking issue: https://github.com/rust-lang/rust/issues/99301
  * RFC (WIP): https://github.com/rust-lang/rfcs/pull/2895
* `provide_any`
  * tracking issue: https://github.com/rust-lang/rust/issues/96024
  * RFC: https://github.com/rust-lang/rfcs/pull/3192

The changes in this PR are intended to address libs meeting feedback summarized by `@Amanieu` in https://github.com/rust-lang/rust/issues/96024#issuecomment-1554773172

The specific items this PR addresses so far are:

> We feel that the names "demand" and "request" are somewhat synonymous and would like only one of those to be used for better consistency.

I went with `Request` here since it sounds nicer, but I'm mildly concerned that at first glance it could be confused with the use of the word in networking context.

> The Provider trait should be deleted and its functionality should be merged into Error. We are happy to only provide an API that is only usable with Error. If there is demand for other uses then this can be provided through an external crate.

The net impact this PR has is that examples which previously looked like
```
    core::any::request_ref::<String>(&err).unwramp()
```

now look like
```
    (&err as &dyn core::error::Error).request_value::<String>().unwrap()
```

These are methods that based on the type hint when called return an `Option<T>` of that type. I'll admit I don't fully understand how that's done, but it involves `core::any::tags::Type` and `core::any::TaggedOption`, neither of which are exposed in the public API, to construct a `Request` which is then passed to the `Error.provide` method.

Something that I'm curious about is whether or not they are essential to the use of `Request` types (prior to this PR referred to as `Demand`) and if so does the fact that they are kept private imply that `Request`s are only meant to be constructed privately within the standard library? That's what it looks like to me.

These methods ultimately call into code that looks like:
```
/// Request a specific value by tag from the `Error`.
fn request_by_type_tag<'a, I>(err: &'a (impl Error + ?Sized)) -> Option<I::Reified>
where
    I: tags::Type<'a>,
{
    let mut tagged = core::any::TaggedOption::<'a, I>(None);
    err.provide(tagged.as_request());
    tagged.0
}
```

As far as the `Request` API is concerned, one suggestion I would like to make is that the previous example should look more like this:
```
/// Request a specific value by tag from the `Error`.
fn request_by_type_tag<'a, I>(err: &'a (impl Error + ?Sized)) -> Option<I::Reified>
where
    I: tags::Type<'a>,
{
    let tagged_request = core::any::Request<I>::new_tagged();
    err.provide(tagged_request);
    tagged.0
}
```
This makes it possible for anyone to construct a `Request` for use in their own projects without exposing an implementation detail like `TaggedOption` in the API surface.

Otherwise noteworthy is that I had to add `pub(crate)` on both `core::any::TaggedOption` and `core::any::tags` since `Request`s now need to be constructed in the `core::error` module. I considered moving `TaggedOption` into the `core::error` module but again I figured it's an implementation detail of `Request` and belongs closer to that.

At the time I am opening this PR, I have not yet looked into the following bit of feedback:

> We took a look at the generated code and found that LLVM is unable to optimize multiple .provide_* calls into a switch table because each call fetches the type id from Erased::type_id separately each time and the compiler doesn't know that these calls all return the same value. This should be fixed.

This is what I'll focus on next while waiting for feedback on the progress so far. I suspect that learning more about the type IDs will help me understand the need for `TaggedOption` a little better.

Co-authored-by: Nklensy <klensy@users.noreply.github.com>

Remove constness from `ImplSource::Param`

Co-authored-by: Nbjorn3 <17426603+bjorn3@users.noreply.github.com>

check for non-defining uses of RPIT

This PR requires defining uses of RPIT and the async functions return type to use unique generic parameters as type and const arguments, (mostly) fixing #111935. This changes the following snippet to an error (it compiled since 1.62):
```rust
fn foo<T>() -> impl Sized {
    let _: () = foo::<u8>(); //~ ERROR non-defining use of `impl Sized`
}
```
Since 1.62 we only checked that the generic arguments of opaque types are unique parameters for TAIT and ignored RPITs, so this PR changes the behavior here to be consistent.

For defining uses which do not have unique params as arguments it is unclear how the hidden type should map to the generic params of the opaque. In the following snippet, should the hidden type of `foo<T>::opaque` be `T` or `u32`.
```rust
fn foo<T>() -> impl Sized {
    let _: u32 = foo::<u32>();
    foo::<T>()
}
```
There are no crater regressions caused by this change.

---

The same issue exists for lifetime arguments which is not fixed by this PR, currently resulting in an ICE in mir borrowck (I wasn't able to get an example which didn't ICE, it might be possible):
```rust
fn foo<'a: 'a>() -> impl Sized {
    let _: &'static () = foo::<'static>();
    //~^ ICE opaque type with non-universal region substs
    foo::<'a>()
}
```
Fixing this for lifetimes as well is blocked on https://github.com/rust-lang/rust/issues/113916. Due to this issue, functions returning an RPIT with lifetime parameters equal in the region constraint graph would always result in an error, resulting in breakage found via crater: https://github.com/rust-lang/rust/pull/112842#issuecomment-1610057887
```rust
trait Trait<'a, 'b> {}
impl Trait<'_, '_> for () {}

struct Type<'a>(&'a ());
impl<'a> Type<'a> {
    // `'b == 'a`
    fn do_stuff<'b: 'a>(&'b self) -> impl Trait<'a, 'b> {
        // This fails as long there is something in the body
        // which adds the outlives constraints to the constraint graph.
        //
        // This is the case for nested closures.
        (|| ())()

    }
}
```

Select obligations before processing wf obligation in `compare_method_predicate_entailment`

We need to select obligations before processing the WF obligation for the `IMPLIED_BOUNDS_ENTAILMENT` lint, since it skips over type variables.

Fixes #114783

r? `@jackh726`

TAITs do not constrain generic params

Fixes #108425

Not sure if I should rework those two failing tests. I guess `tests/ui/type-alias-impl-trait/coherence.rs` could just have the type parameter removed from it? IDK what `tests/ui/type-alias-impl-trait/coherence_generalization.rs` is even testing, though.

r? `@aliemjay`
cc `@lcnr` `@oli-obk` (when he's back from 🌴)

Rollup of 5 pull requests

Successful merges:

 - #94667 (Add `Iterator::map_windows`)
 - #114069 (Allow using external builds of the compiler-rt profile lib)
 - #114354 (coverage: Store BCB counter info externally, not directly in the BCB graph)
 - #114625 (CI: use smaller machines in PR runs)
 - #114777 (Migrate GUI colors test to original CSS color format)

r? `@ghost`
`@rustbot` modify labels: rollup

* remove `impl Provider for Error`
* rename `Demand` to `Request`
* update docstrings to focus on the conceptual API provided by `Request`
* move `core::any::{request_ref, request_value}` functions into `core::error`
* move `core::any::tag`, `core::any::Request`, an `core::any::TaggedOption` into `core::error`
* replace `provide_any` feature name w/ `error_generic_member_access`
* move `core::error::request_{ref,value} tests into core::tests::error module
* update unit and doc tests

Migrate GUI colors test to original CSS color format

Follow-up of https://github.com/rust-lang/rust/pull/111459.

r? `@notriddle`

CI: use smaller machines in PR runs

mingw-check job-linux-16c -> job-linux-4c
~job-linux-4c 20 min in auto job
~job-linux-16c 13 min in pr job
with current pr regressed to almost 21 min, it's ok.

mingw-check-tidy job-linux-16c -> job-linux-4c small enough, so reduce to minimal
~ job-linux-16c 3 min
with current pr regressed to almost 5 min, it's ok.

x86_64-gnu-tools job-linux-16c this is top job by time in PR, so don't touch it
~ job-linux-8c 1.30 hour in auto job
~ job-linux-16c 1 hour in pr job (affected by #114613, actual time ~ 30 min)

x86_64-gnu-llvm-15 job-linux-16c don't change too
~ job-linux-8c 1.30 hour in auto job
~ job-linux-16c 30 min in pr job

Noticed while working on https://github.com/rust-lang/rust/pull/114621, so current time affected by always rebuilded docker images (but pr images always rebuilded before too, so nvm)

coverage: Store BCB counter info externally, not directly in the BCB graph

When deciding how to instrument the underlying MIR for coverage, the `InstrumentCoverage` pass builds a simplified “Basic Counter Block” graph, and then allocates coverage counters/expressions to various nodes/edges in the BCB graph as necessary. Those counters/expressions are then injected into the function's MIR.

The awkward thing here is that the code for doing this needs `&mut` access to the graph, in order to associate coverage info with individual nodes, even though it isn't making any structural changes to the graph itself. That makes it harder to understand and modify the instrumentation code.

In addition, the graph alone can't hold all the information that is needed. There ends up being an extra vector of “intermediate expressions” that needs to be passed around separately anyway.

---

This PR simplifies things by instead storing all of that temporary coverage information in a number of side-tables inside `CoverageCounters`.

This makes it easier to see all of the information produced by the make-counters step, and how it is used by the inject-into-mir step.

---

Looking at the combined changes is possible, but I recommend reviewing the commits individually, because the big changes are mostly independent of each other (despite being conceptually related).

Allow using external builds of the compiler-rt profile lib

This changes the bootstrap config `target.*.profiler` from a plain bool
to also allow a string, which will be used as a path to the pre-built
profiling runtime for that target. Then `profiler_builtins/build.rs`
reads that in a `LLVM_PROFILER_RT_LIB` environment variable.