Co-authored-by: Janusz Marcinkiewicz <virrages@gmail.com>

…er writes do

… into_pointer_or_addr

Previously we only exposed a kreg register class which excludes the k0
register since it can't be used in many instructions. However k0 is a
valid register and we need to have a way of marking it as clobbered for
clobber_abi.

Fixes rust-lang#94977

asm: Add a kreg0 register class on x86 which includes k0

Previously we only exposed a kreg register class which excludes the k0
register since it can't be used in many instructions. However k0 is a
valid register and we need to have a way of marking it as clobbered for
clobber_abi.

Fixes rust-lang#94977

…=GuillaumeGomez

Remove extra space before a where clause

Remove extra space before where clause in the generated documentation.

The fix is to move the space before the break-line so that it doesn't appear visually but is still here. Removing it completely would create things like this `impl<D> Delta<D>where D: MyTrait` (missing a space before the where) which I don't think we want.

Added two regression test, first one test that the `<br>` is after the space and the second check that the `<br>` is before the spaces.

Before:
![image](https://user-images.githubusercontent.com/3616612/162475212-d4bb6727-ed66-4a55-a4a2-4f55189bf8bd.png)

After:
![image](https://user-images.githubusercontent.com/3616612/162475467-508fd082-60a7-4a8c-b693-8b188e8843e6.png)

r? ``@GuillaumeGomez``

…lan-DPC

Refactor loop into iterator; simplify negation logic.

is_dummy should return when a non-dummy is found, but instead is iterated until completion. With some inspiration from line 323 this was refactored to a single line that returns once a single counterexample is found.

interpret: Fix writing uninit to an allocation

When calling `mark_init`, we need to also be mindful of what happens with the relocations! Specifically, when we de-init memory, we need to clear relocations in that range as well or else strange things will happen (and printing will not show the de-init, since relocations take precedence there).

Fixes rust-lang/miri#2068.

Here's the Miri testcase that this fixes (requires `-Zmiri-disable-validation`):
```rust
use std::mem::MaybeUninit;

fn main() { unsafe {
    let mut x = MaybeUninit::<i64>::uninit();
    // Put in a ptr.
    x.as_mut_ptr().cast::<&i32>().write_unaligned(&0);
    // Overwrite parts of that pointer with 'uninit' through a Scalar.
    let ptr = x.as_mut_ptr().cast::<i32>();
    *ptr = MaybeUninit::uninit().assume_init();
    // Reading this back should hence work fine.
    let _c = *ptr;
} }
```
Previously this failed with
```
error: unsupported operation: unable to turn pointer into raw bytes
  --> ../miri/uninit.rs:11:14
   |
11 |     let _c = *ptr;
   |              ^^^^ unable to turn pointer into raw bytes
   |
   = help: this is likely not a bug in the program; it indicates that the program performed an operation that the interpreter does not support

   = note: inside `main` at ../miri/uninit.rs:11:14
```

…=oli-obk

Miri provenance cleanup

Reviewing rust-lang#95826 by ``@carbotaniuman`` made me realize that we could clean things up a little here.

``@carbotaniuman`` please let me know if you're okay with landing this (it will create a lot of conflicts with your PR), or if you'd prefer incorporating the ideas from this PR into yours. I think we want to end up in a situation where the function you called `ptr_reify_alloc` returns just two things, a concrete tag and an offset. Getting an `AllocId` from a concrete tag should be infallible like now. However a concrete tag and `Tag` don't have to be the same type.

r? ``@oli-obk``

…homcc

Use futex locks on emscripten.

This switches Emscripten to the futex-based lock implementations, away from pthread.

Tracking issue: rust-lang#93740