…ers and Rust plans to set Windows 10 as the minimum supported OS for target x86_64-pc-windows-msvc, I have added the cmpxchg16b and sse3 feature (as CPUs that meet the Windows 10 64-bit requirement also support SSE3. See https://walbourn.github.io/directxmath-sse3-and-ssse3/ )

Fixed a bug where adding CMPXCHG16B would fail due to different names in Rustc and LLVM

As CMPXCHG16B is supported, I updated the max atomic width to 128-bits from 64-bits

Updated x86_64-uwp-windows-gnu to use CMPXCHG16B and SSE3

…rdins!)

This gives one extra error message on one test, but is necessary to fix
bigger problems caused by the cancellation of stashed errors.

(Note: why not just avoid stashing altogether? Because that resulted in
additional output changes.)

This gives one extra error message on two tests, but is necessary to fix
bigger problems caused by the cancellation of stashed errors.

(Note: why not just avoid stashing altogether? Because that resulted in
additional output changes.)

Stashed errors used to be counted as errors, but could then be
cancelled, leading to `ErrorGuaranteed` soundness holes. rust-lang#120828 changed
that, closing the soundness hole. But it introduced other difficulties
because you sometimes have to account for pending stashed errors when
making decisions about whether errors have occured/will occur and it's
easy to overlook these.

This commit aims for a middle ground.
- Stashed errors (not warnings) are counted immediately as emitted
  errors, avoiding the possibility of forgetting to consider them.
- The ability to cancel (or downgrade) stashed errors is eliminated, by
  disallowing the use of `steal_diagnostic` with errors, and introducing
  the more restrictive methods `try_steal_{modify,replace}_and_emit_err`
  that can be used instead.

Other things:
- `DiagnosticBuilder::stash` and `DiagCtxt::stash_diagnostic` now both
  return `Option<ErrorGuaranteed>`, which enables the removal of two
  `delayed_bug` calls and one `Ty::new_error_with_message` call. This is
  possible because we store error guarantees in
  `DiagCtxt::stashed_diagnostics`.
- Storing the guarantees also saves us having to maintain a counter.
- Calls to the `stashed_err_count` method are no longer necessary
  alongside calls to `has_errors`, which is a nice simplification, and
  eliminates two more `span_delayed_bug` calls and one FIXME comment.
- Tests are added for three of the four fixed PRs mentioned below.
- `issue-121108.rs`'s output improved slightly, omitting a non-useful
  error message.

Fixes rust-lang#121451.
Fixes rust-lang#121477.
Fixes rust-lang#121504.
Fixes rust-lang#121508.

This undoes the changes from rust-lang#121482 and rust-lang#121586, now that stashed errors
will trigger more early aborts.

Seems wise, since it shouldn't proceed in that case.

I removed it in rust-lang#121206 because I thought thought it wasn't necessary.
But then I had to add an `emit_stashed_diagnostics` call elsewhere in
rustfmt to avoid the assertion failure (which took two attempts to get
right, rust-lang#121487 and rust-lang#121615), and now there's an assertion failure in
clippy as well (rust-lang/rust-clippy#12364).

So this commit just reinstates the call in `DiagCtxtInner::drop`. It
also reverts the rustfmt changes from rust-lang#121487 and rust-lang#121615, though it
keeps the tests added for those PRs.

In practice, 'a and 'b and 'c are always the same. This change makes
`UnusedExterns` more like `ArtifactNotification`, which uses a single
lifetime 'a in multiple ways.

This `HumanEmitter` is only created to test if it supports colour. The
diagnostic width isn't relevant.

It only has two call sites, and one of those doesn't set the source map.

Because it's now the only constructor.

They have the same signature, and the former just calls the latter.

And likewise with `ColorConfig::suggests_using_colors`. They both have a
single call site. And note that `BufWriter::supports_color()` always
returns false, which enables a small bit of constant folding along the
way.

Because `HumanEmitter::new` is enough, in conjunction with the (renamed)
`stderr_destination` function.

They are so similar to `JsonEmitter::new` it's not worth having separate
functions, it makes the code harder to read.

Use `derive(Setters)` to derive setters, and then change
`JsonEmitter::new` to only have the arguments that are always used.

It took me a while to work this out.

…enkov,ChrisDenton

Enable CMPXCHG16B, SSE3, SAHF/LAHF and 128-bit Atomics (in nightly) in Windows x64

As Rust plans to set Windows 10 as the minimum supported OS for target x86_64-pc-windows-msvc, I have added the cmpxchg16b and sse3 feature. Windows 10 requires CMPXCHG16B, LAHF/SAHF, and PrefetchW as stated in the requirements [here](https://download.microsoft.com/download/c/1/5/c150e1ca-4a55-4a7e-94c5-bfc8c2e785c5/Windows%2010%20Minimum%20Hardware%20Requirements.pdf). Furthermore, CPUs that meet these requirements also have SSE3 ([see](https://walbourn.github.io/directxmath-sse3-and-ssse3/))

…ler-errors

pattern_analysis: rework how we hide empty private fields

Consider this:
```rust
mod foo {
  pub struct Bar {
    pub a: bool,
    b: !,
  }
}

fn match_a_bar(bar: foo::Bar) -> bool {
  match bar {
    Bar { a, .. } => a,
  }
}
```

Because the field `b` is private, matches outside the module are not allowed to observe the fact that `Bar` is empty. In particular `match bar {}` is valid within the module `foo` but an error outside (assuming `exhaustive_patterns`).

We currently handle this by hiding the field `b` when it's both private and empty. This means that the pattern `Bar { a, .. }` is lowered to `Bar(a, _)` if we're inside of `foo` and to `Bar(a)` outside. This involves a bit of a dance to keep field indices straight. But most importantly this makes pattern lowering depend on the module.

In this PR, I instead do nothing special when lowering. Only during analysis do we track whether a place must be skipped.

r? `@compiler-errors`

Skip unnecessary comparison with half-open range patterns

This is the last remaining detail in the implementation of half-open range patterns. Until now, a half-open range pattern like `10..` was converted to `10..T::MAX` before lowering to MIR, which generated an extra pointless comparison. With this PR we don't generate it.

Use volatile access instead of `#[used]` for `on_tls_callback`

The first commit adds a volatile load of `p_thread_callback` when registering a dtor so that the compiler knows if the callback is used or not. I don't believe the added volatile instruction is otherwise significant in the context. In my testing using the volatile load allowed the compiler to correctly reason about whether `on_tls_callback` is used or not, allowing it to be omitted entirely in some cases. Admittedly it usually is used due to `Thread` but that can be avoided (e.g. in DLLs or with custom entry points that avoid the offending APIs). Ideally this would be something the compiler could help a bit more with so we didn't have to use tricks like `#[used]` or volatile. But alas.

I also used this as an opportunity to clean up the `unused` lints which I don't think serve a purpose any more.

The second commit removes the volatile load of `_tls_used` with `#cfg[target_thread_local]` because `#[thread_local]` already implies it. And if it ever didn't then `#[thread_local]` would be broken when there aren't any dtors.

…in, r=estebank

Count stashed errors again

Stashed diagnostics are such a pain. Their "might be emitted, might not" semantics messes with lots of things.

rust-lang#120828 and rust-lang#121206 made some big changes to how they work, improving some things, but still leaving some problems, as seen by the issues caused by rust-lang#121206. This PR aims to fix all of them by restricting them in a way that eliminates the "might be emitted, might not" semantics while still allowing 98% of their benefit. Details in the individual commit logs.

r? `@oli-obk`

…i-obk

Emitter cleanups

Some cleanups I made when reading emitter code. In particular, `HumanEmitter` and `JsonEmitter` have gone from three constructors to one.

r? `@oli-obk`