…clif-2023-11-25

…orn3

Subtree sync for rustc_codegen_cranelift

The main highlights this time are implementing a bunch of new vendor intrinsics and fixing some existing ones. And fixing polymorphization for coroutines.

r? `@ghost`

`@rustbot` label +A-codegen +A-cranelift +T-compiler

Add Windows wrappers for ./y

Currently, `Handler::fatal` returns `FatalError`. But `Session::fatal`
returns `!`, because it calls `Handler::fatal` and then calls `raise` on
the result. This inconsistency is unfortunate.

This commit changes `Handler::fatal` to do the `raise` itself, changing
its return type to `!`. This is safe because there are only two calls to
`Handler::fatal`, one in `rustc_session` and one in
`rustc_codegen_cranelift`, and they both call `raise` on the result.

`HandlerInner::fatal` still returns `FatalError`, so I renamed it
`fatal_no_raise` to emphasise the return type difference.

…inter is immutable

…saethlin

compile-time evaluation: detect writes through immutable pointers

This has two motivations:
- it unblocks rust-lang#116745 (and therefore takes a big step towards `const_mut_refs` stabilization), because we can now detect if the memory that we find in `const` can be interned as "immutable"
- it would detect the UB that was uncovered in rust-lang#117905, which was caused by accidental stabilization of `copy` functions in `const` that can only be called with UB

When UB is detected, we emit a future-compat warn-by-default lint. This is not a breaking change, so completely in line with [the const-UB RFC](https://rust-lang.github.io/rfcs/3016-const-ub.html), meaning we don't need t-lang FCP here. I made the lint immediately show up for dependencies since it is nearly impossible to even trigger this lint without `const_mut_refs` -- the accidentally stabilized `copy` functions are the only way this can happen, so the crates that popped up in rust-lang#117905 are the only causes of such UB (in the code that crater covers), and the three cases of UB that we know about have all been fixed in their respective crates already.

The way this is implemented is by making use of the fact that our interpreter is already generic over the notion of provenance. For CTFE we now use the new `CtfeProvenance` type which is conceptually an `AllocId` plus a boolean `immutable` flag (but packed for a more efficient representation). This means we can mark a pointer as immutable when it is created as a shared reference. The flag will be propagated to all pointers derived from this one. We can then check the immutable flag on each write to reject writes through immutable pointers.

I just hope perf works out.

This maps to the LLVM intrinsics: llvm.masked.load and llvm.masked.store

detects redundant imports that can be eliminated.

for rust-lang#117772 :

In order to facilitate review and modification, split the checking code and
removing redundant imports code into two PR.

…, r=davidtwco

Add lint against ambiguous wide pointer comparisons

This PR is the resolution of rust-lang#106447 decided in rust-lang#117717 by T-lang.

## `ambiguous_wide_pointer_comparisons`

*warn-by-default*

The `ambiguous_wide_pointer_comparisons` lint checks comparison of `*const/*mut ?Sized` as the operands.

### Example

```rust
let ab = (A, B);
let a = &ab.0 as *const dyn T;
let b = &ab.1 as *const dyn T;

let _ = a == b;
```

### Explanation

The comparison includes metadata which may not be expected.

-------

This PR also drops `clippy::vtable_address_comparisons` which is superseded by this one.

~~One thing: is the current naming right? `invalid` seems a bit too much.~~

Fixes rust-lang#117717

…WaffleLapkin

codegen: panic when trying to compute size/align of extern type

The alignment is also computed when accessing a field of extern type at non-zero offset, so we also panic in that case.

Previously `size_of_val` worked because the code path there assumed that "thin pointer" means "sized". But that's not true any more with extern types. The returned size and align are just blatantly wrong, so it seems better to panic than returning wrong results. We use a non-unwinding panic since code probably does not expect size_of_val to panic.

This matches type_has_metadata in cg_ssa and doesn't require computing
the layout of the type. It is also a bit faster.

…ait tail

cc rust-lang#118538

cc rust-lang#118540
Fixes rust-lang/rustc_codegen_cranelift#1435

…clif-2023-12-19