…owedBuf` and `BorrowedCursor`)

This caused several performance regressions because of existing code
which uses `Read::read` and therefore requires full buffer
initialization. This is particularly a problem when the same buffer is
re-used for multiple read calls since this means it needs to be fully
re-initialized each time.

There is still some benefit to landing the API changes, but we will have
to add private APIs so that the existing infrastructure can
track and avoid redundant initialization.

…ng, r=lqd

Correctly encode doc attribute metadata

Follow-up of rust-lang#149645.

The change I made was slightly wrong. [Originally](https://github.com/rust-lang/rust/pull/149645/changes#diff-72bf3e63aae0c5f24a5ce78a560db321ac6ead9df5ada3e33462a7f7d6218a55) the check was:

```rust
        if let Some(item_list) = attr.meta_item_list() {
            for item in item_list {
                if !item.has_name(sym::inline) {
```

So we were checking that there was no `doc(inline)` attribute. This PR should fix it.

r? ``@lqd``

mir_build: Rename `TestCase` to `TestableCase`

In the spirit of rust-lang#149946, this is another renaming of something I've always found confusing.

When lowering match conditions, there is a subtle distinction between the kind of *test* being performed (on a scrutinee place), the possible outcomes of that test, and the different “cases” (corresponding to pattern nodes) that the test is distinguishing. Cases imply a particular preferred test, but once a test is chosen it can also interact with other cases as well.

I have often mixed up `TestKind` and `TestCase`, since the names are so similar, and they share several variant names. Therefore, this PR renames `TestCase` to `TestableCase`, to emphasise that these are the things selected by whatever test is being performed.

There should be no change to compiler behaviour.

…fJung

miri: add `miri_spin_loop` to make `hint::spin_loop` work consistently

fixes rust-lang#150050

Always use the same implementation when running miri (regardless of target, for consistency). This implementation yields the current thread to try find actual bugs.

r? RalfJung

…sDenton

Revert rust-lang#148937

rust-lang#148937:  Remove initialized-bytes tracking from `BorrowedBuf` and `BorrowedCursor`

This caused several performance regressions because of existing code which uses `Read::read` and therefore requires full buffer initialization. This is particularly a problem when the same buffer is re-used for multiple read calls since this means it needs to be fully re-initialized each time.

There is still some benefit to landing the API changes, but we will have to add private APIs so that the existing infrastructure can track and avoid redundant initialization.