Remove hir::CrateItem.

The crate span is exactly the crate module's inner span. There is no need to store it twice.

rustdoc: Only look at blanket impls in `get_blanket_impls`

The idea here is that all the work in https://github.com/rust-lang/rust/blob/16156fb2787f745e57504197bd7fe38b69c6cbea/compiler/rustc_middle/src/ty/trait_def.rs#L172-L186 doesn't matter for `get_blanket_impls` - Rustdoc will already pick up on those blocks when it documents the item.

Run LLVM coverage instrumentation passes before optimization passes

This matches the behavior of Clang and allows us to remove several
hacks which were needed to ensure functions weren't optimized away
before reaching the instrumentation pass.

Fixes #83429

cc `@richkadel`

r? `@tmandry`

Rollup of 6 pull requests

Successful merges:

 - #80720 (Make documentation of which items the prelude exports more readable.)
 - #83654 (Do not emit a suggestion that causes the E0632 error)
 - #83671 (Add a regression test for issue-75801)
 - #83678 (Fix Self keyword doc URL conflict on case insensitive file systems (until definitely fixed on rustdoc))
 - #83680 (Update for loop desugaring docs)
 - #83683 (bootstrap: don't complain about linkcheck if it is excluded)

Failed merges:

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

bootstrap: don't complain about linkcheck if it is excluded

We don't need to complain to the user about linkcheck having different
hosts and targets when it is already excluded.

Resolves #83661

Update for loop desugaring docs

It looks like the documentation for `for` loops was not updated to match the new de-sugaring process.

Fix Self keyword doc URL conflict on case insensitive file systems (until definitely fixed on rustdoc)

This is just a hack to allow rustup to work on macOS and windows again to distribute std documentation (hopefully once https://github.com/rust-lang/rfcs/pull/3097 or an equivalent is merged).

Fixes https://github.com/rust-lang/rust/issues/80504. Prevents https://github.com/rust-lang/rust/issues/83154 and https://github.com/rust-lang/rustup/issues/2694 in future releases.

cc ``@kinnison``
r? ``@jyn514``

Add a regression test for issue-75801

Closes #75801
r? ``@Aaron1011``

Do not emit a suggestion that causes the E0632 error

Fixes #83606

Make documentation of which items the prelude exports more readable.

I recently figured out that rustdoc allows link inside of inline code blocks as long as they’re delimited with `<code> </code>` instead of `` ` ` ``. I think this applies nicely in the listing of prelude exports [in the docs](https://doc.rust-lang.org/std/prelude/index.html). There, currently unformatted `::` and `{ , }` is used in order to mimick import syntax while attatching links to individual identifiers.

## Rendered Comparison
### Currently (light)
![Screenshot_20210105_155801](https://user-images.githubusercontent.com/3986214/103661510-1a87be80-4f6f-11eb-8360-1dfb23f732e8.png)

### After this PR (light)
![Screenshot_20210105_155811](https://user-images.githubusercontent.com/3986214/103661533-1f4c7280-4f6f-11eb-89d4-874793937824.png)

### Currently (dark)
![Screenshot_20210105_155824](https://user-images.githubusercontent.com/3986214/103661571-2a9f9e00-4f6f-11eb-95f9-e291b5570b41.png)

### After this PR (dark)
![Screenshot_20210105_155836](https://user-images.githubusercontent.com/3986214/103661592-2ffce880-4f6f-11eb-977a-82afcb07d331.png)

### Currently (ayu)
![Screenshot_20210105_155917](https://user-images.githubusercontent.com/3986214/103661619-39865080-4f6f-11eb-9ca1-9045a107cddd.png)

### After this PR (ayu)
![Screenshot_20210105_155923](https://user-images.githubusercontent.com/3986214/103661652-3db26e00-4f6f-11eb-82b7-378e38f0c41f.png)

_Edit:_ I just noticed, the “current” screenshots are from stable, so there are a few more differences in the pictures than the ones from just this PR.

Disallow octal format in Ipv4 string

In its original specification, leading zero in Ipv4 string is interpreted
as octal literals. So a IP address 0127.0.0.1 actually means 87.0.0.1.

This confusion can lead to many security vulnerabilities. Therefore, in
[IETF RFC 6943], it suggests to disallow octal/hexadecimal format in Ipv4
string all together.

Existing implementation already disallows hexadecimal numbers. This commit
makes Parser reject octal numbers.

Fixes #83648.

[IETF RFC 6943]: https://tools.ietf.org/html/rfc6943#section-3.1.1

We don't need to complain to the user about linkcheck having different
hosts and targets when it is already excluded. This can be achieved by
moving the check to when the step is run instead of in should_run.

Replace tabs in err messages before rendering

This is done in other call sites, but was missing in one place.

Fixes #83638

Simplify Command::spawn (no semantic change)

This minimizes the size of an unsafe block, and allows outdenting some
complex code.

Rollup of 7 pull requests

Successful merges:

 - #83568 (update comment at MaybeUninit::uninit_array)
 - #83571 (Constantify some slice methods)
 - #83579 (Improve pointer arithmetic docs)
 - #83645 (Wrap non-pre code blocks)
 - #83656 (Add a regression test for issue-82865)
 - #83662 (Update books)
 - #83667 (Suggest box/pin/arc ing receiver on method calls)

Failed merges:

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

Suggest box/pin/arc ing receiver on method calls

_Extracted from https://fasterthanli.me/articles/pin-and-suffering_

Update books

## reference

4 commits in d10a0af8dca25d9d548ca6a369fd66ad06acb3c9..fd97729e2d82f8b08d68a31c9bfdf0c37a7fd542
2021-03-21 11:14:06 -0700 to 2021-03-28 14:29:19 -0700
- Editorial cleanup on expressions (part 1) (rust-lang-nursery/reference#967)
- Update type casts section (rust-lang-nursery/reference#961)
- Add missing "?" notion (rust-lang-nursery/reference#989)
- Fix typo (rust-lang-nursery/reference#988)

## book

8 commits in fc2f690fc16592abbead2360cfc0a42f5df78052..b54090a99ec7c4b46a5203a9c927fdbc311bb1f5
2021-03-05 14:03:22 -0500 to 2021-03-24 11:21:46 -0500
- correct the signature of the `deref` method (rust-lang/book#2658)
- Clarify the immutability of a reference (rust-lang/book#2646)
- Tweak wording around Windows representation of enter
- Ch. 02 note - Enter results in CRLF on Windows (rust-lang/book#2648)
- Added an example of slicing result (rust-lang/book#2649)
- Fix word wrapping, mention dictionary.txt is also in the ci dir
- README: note that spellcheck.sh is in ci directory (rust-lang/book#2652)
- Change someurl.com to example.org (rust-lang/book#2655)

## rust-by-example

12 commits in eead22c6c030fa4f3a167d1798658c341199e2ae..29d91f591c90dd18fdca6d23f1a9caf9c139d0d7
2021-03-04 16:26:43 -0300 to 2021-03-23 09:03:39 -0300
- Unwrap some drinks. (rust-lang/rust-by-example#1431)
- doc(testcase_linked_list): add a little extra note about pattern (rust-lang/rust-by-example#1408)
- Update function name in comment (rust-lang/rust-by-example#1413)
- Fixes minor typo in src/types/cast.md (rust-lang/rust-by-example#1414)
- Add destructuring example to generics new type (rust-lang/rust-by-example#1416)
- update struct.md (rust-lang/rust-by-example#1419)
- fix name from rectangle to Rectangle (rust-lang/rust-by-example#1420)
- Typo "incures" in code comment (rust-lang/rust-by-example#1422)
- Changed impl to use Self::Item (rust-lang/rust-by-example#1425)
- Fix code highlighting in some places (rust-lang/rust-by-example#1427)
- Update multi_bounds.md (rust-lang/rust-by-example#1428)
- Reformulated text for redability (rust-lang/rust-by-example#1429)

## rustc-dev-guide

3 commits in 67ebd4b55dba44edfc351621cef6e5e758169c55..0687daac28939c476df51778f5a1d1aff1a3fddf
2021-03-11 13:36:25 -0800 to 2021-03-28 13:33:56 -0400
- Add notes about nightly rustc version for the rustc-driver examples
- Update rustc-driver-*.rs examples (rust-lang/rustc-dev-guide#1095)
- Fix rust compiler meeting info (rust-lang/rustc-dev-guide#1087)

## embedded-book

1 commits in f61685755fad7d3b88b4645adfbf461d500563a2..d3f2ace94d51610cf3e3c265705bb8416d37f8e4
2021-03-08 01:06:44 +0000 to 2021-03-17 07:53:09 +0000
- Add binary attribute to .jpeg files, closes rust-embedded/book#287  (rust-embedded/book#288)

Add a regression test for issue-82865

Closes #82865
r? `@petrochenkov`

Wrap non-pre code blocks

Fix #83550 regression

```
$ cargo new --lib whitespace && cd whitespace && echo '//! `"   foo   "`' > src/lib.rs && cargo doc --open
```

Before

![](https://user-images.githubusercontent.com/89623/112713498-c0dfc200-8ed5-11eb-8c57-efdf26372e74.png)

After

![](https://user-images.githubusercontent.com/89623/112713538-f08eca00-8ed5-11eb-8a98-675179f60ae2.png)

r? ``@GuillaumeGomez``
cc ``@mgeisler``

Improve pointer arithmetic docs

* Add slightly more detailed definition of "allocated object" to the module docs, and link it from everywhere.
* Clarify the "remains attached" wording a bit (at least I hope this is clearer).
* Remove the sentence about using integer arithmetic; this seems to confuse people even if it is technically correct.

As usual, the edit needs to be done in a dozen places to remain consistent, I hope I got them all.

Constantify some slice methods

Tracking issue: #83570

This PR constantifies the following functions under feature `const_slice_first_last`:
- `slice::first`
- `slice::split_first`
- `slice::last`
- `slice::split_last`

Blocking on `#![feature(const_mut_refs)]`:
- `slice::first_mut`
- `slice::split_first_mut`
- `slice::last_mut`
- `slice::split_last_mut`

update comment at MaybeUninit::uninit_array

https://github.com/rust-lang/rust/issues/49147 is closed; this now instead needs inline const expressions (#76001).

Clean up Vec's benchmarks

The Vec benchmarks need a lot of love. I sort of noticed this in https://github.com/rust-lang/rust/pull/83357 but the overall situation is much less awesome than I thought at the time. The first commit just removes a lot of asserts and does a touch of other cleanup.

A number of these benchmarks are poorly-named. For example, `bench_map_fast` is not in fact fast, `bench_rev_1` and `bench_rev_2` are vague, `bench_in_place_zip_iter_mut` doesn't call `zip`, `bench_in_place*` don't do anything in-place... Should I fix these, or is there tooling that depend on the names not changing?

I've also noticed that `bench_rev_1` and `bench_rev_2` are remarkably fragile. It looks like poking other code in `Vec` can cause the codegen of this benchmark to switch to a version that has almost exactly half its current throughput and I have absolutely no idea why.

Here's the fast version:
```asm
  0.69 │110:   movdqu -0x20(%rbx,%rdx,4),%xmm0
  1.76 │       movdqu -0x10(%rbx,%rdx,4),%xmm1
  0.71 │       pshufd $0x1b,%xmm1,%xmm1
  0.60 │       pshufd $0x1b,%xmm0,%xmm0
  3.68 │       movdqu %xmm1,-0x30(%rcx)
 14.36 │       movdqu %xmm0,-0x20(%rcx)
 13.88 │       movdqu -0x40(%rbx,%rdx,4),%xmm0
  6.64 │       movdqu -0x30(%rbx,%rdx,4),%xmm1
  0.76 │       pshufd $0x1b,%xmm1,%xmm1
  0.77 │       pshufd $0x1b,%xmm0,%xmm0
  1.87 │       movdqu %xmm1,-0x10(%rcx)
 13.01 │       movdqu %xmm0,(%rcx)
 38.81 │       add    $0x40,%rcx
  0.92 │       add    $0xfffffffffffffff0,%rdx
  1.22 │     ↑ jne    110
```
And the slow one:
```asm
  0.42 │9a880:   movdqa     %xmm2,%xmm1
  4.03 │9a884:   movq       -0x8(%rbx,%rsi,4),%xmm4
  8.49 │9a88a:   pshufd     $0xe1,%xmm4,%xmm4
  2.58 │9a88f:   movq       -0x10(%rbx,%rsi,4),%xmm5
  7.02 │9a895:   pshufd     $0xe1,%xmm5,%xmm5
  4.79 │9a89a:   punpcklqdq %xmm5,%xmm4
  5.77 │9a89e:   movdqu     %xmm4,-0x18(%rdx)
 15.74 │9a8a3:   movq       -0x18(%rbx,%rsi,4),%xmm4
  3.91 │9a8a9:   pshufd     $0xe1,%xmm4,%xmm4
  5.04 │9a8ae:   movq       -0x20(%rbx,%rsi,4),%xmm5
  5.29 │9a8b4:   pshufd     $0xe1,%xmm5,%xmm5
  4.60 │9a8b9:   punpcklqdq %xmm5,%xmm4
  9.81 │9a8bd:   movdqu     %xmm4,-0x8(%rdx)
 11.05 │9a8c2:   paddq      %xmm3,%xmm0
  0.86 │9a8c6:   paddq      %xmm3,%xmm2
  5.89 │9a8ca:   add        $0x20,%rdx
  0.12 │9a8ce:   add        $0xfffffffffffffff8,%rsi
  1.16 │9a8d2:   add        $0x2,%rdi
  2.96 │9a8d6: → jne        9a880 <<alloc::vec::Vec<T,A> as core::iter::traits::collect::Extend<&T>>::extend+0xd0>
```

Don't duplicate the extern providers once for each crate

This should give a small perf improvement for small crates by avoiding a memcpy of a pretty big struct for each loaded crate. In addition would be useful for replacing the sequential `CrateNum` everywhere with the hash based `StableCrateId` introduced in #81635, which would allow avoiding remapping of `CrateNum`'s when loading crate metadata. While this PR is not strictly needed for that, it is necessary to prevent a performance loss due to it.

I think this duplication was done in https://github.com/rust-lang/rust/pull/40008 (which introduced the query system) to make it possible to compile multiple crates in a single session in the future. I think this is unlikely to be implemented any time soon. In addition this PR can easily be reverted if necessary to implement this.

Reduce the impact of Vec::reserve calls that do not cause any allocation

I think a lot of callers expect `Vec::reserve` to be nearly free when no resizing is required, but unfortunately that isn't the case. LLVM makes remarkably poor inlining choices (along the path from `Vec::reserve` to `RawVec::grow_amortized`), so depending on the surrounding context you either get a huge blob of `RawVec`'s resizing logic inlined into some seemingly-unrelated function, or not enough inlining happens and/or the actual check in `needs_to_grow` ends up behind a function call. My goal is to make the codegen for `Vec::reserve` match the mental that callers seem to have: It's reliably just a `sub cmp ja` if there is already sufficient capacity.

This patch has the following impact on the serde_json benchmarks: https://github.com/serde-rs/json-benchmark/tree/ca3efde8a5b75ff59271539b67452911860248c7 run with `cargo +stage1 run --release -- -n 1024`

Before:
```
                                DOM                  STRUCT
======= serde_json ======= parse|stringify ===== parse|stringify ====
data/canada.json         340 MB/s   490 MB/s   630 MB/s   370 MB/s
data/citm_catalog.json   460 MB/s   540 MB/s  1010 MB/s   550 MB/s
data/twitter.json        330 MB/s   840 MB/s   640 MB/s   630 MB/s

======= json-rust ======== parse|stringify ===== parse|stringify ====
data/canada.json         580 MB/s   990 MB/s
data/citm_catalog.json   720 MB/s   660 MB/s
data/twitter.json        570 MB/s   960 MB/s
```

After:
```
                                DOM                  STRUCT
======= serde_json ======= parse|stringify ===== parse|stringify ====
data/canada.json         330 MB/s   510 MB/s   610 MB/s   380 MB/s
data/citm_catalog.json   450 MB/s   640 MB/s   970 MB/s   830 MB/s
data/twitter.json        330 MB/s   880 MB/s   670 MB/s   960 MB/s

======= json-rust ======== parse|stringify ===== parse|stringify ====
data/canada.json         560 MB/s  1130 MB/s
data/citm_catalog.json   710 MB/s   880 MB/s
data/twitter.json        530 MB/s  1230 MB/s

```

That's approximately a one-third increase in throughput on two of the benchmarks, and no effect on one (The benchmark suite has sufficient jitter that I could pick a run where there are no regressions, so I'm not convinced they're meaningful here).

This also produces perf increases on the order of 3-5% in a few other microbenchmarks that I'm tracking. It might be useful to see if this has a cascading effect on inlining choices in some large codebases.

Compiling this simple program demonstrates the change in codegen that causes the perf impact:
```rust
fn main() {
    reserve(&mut Vec::new());
}

#[inline(never)]
fn reserve(v: &mut Vec<u8>) {
    v.reserve(1234);
}
```

Before:
```rust
00000000000069b0 <scratch::reserve>:
    69b0:       53                      push   %rbx
    69b1:       48 83 ec 30             sub    $0x30,%rsp
    69b5:       48 8b 47 08             mov    0x8(%rdi),%rax
    69b9:       48 8b 4f 10             mov    0x10(%rdi),%rcx
    69bd:       48 89 c2                mov    %rax,%rdx
    69c0:       48 29 ca                sub    %rcx,%rdx
    69c3:       48 81 fa d1 04 00 00    cmp    $0x4d1,%rdx
    69ca:       77 73                   ja     6a3f <scratch::reserve+0x8f>
    69cc:       48 81 c1 d2 04 00 00    add    $0x4d2,%rcx
    69d3:       72 75                   jb     6a4a <scratch::reserve+0x9a>
    69d5:       48 89 fb                mov    %rdi,%rbx
    69d8:       48 8d 14 00             lea    (%rax,%rax,1),%rdx
    69dc:       48 39 ca                cmp    %rcx,%rdx
    69df:       48 0f 47 ca             cmova  %rdx,%rcx
    69e3:       48 83 f9 08             cmp    $0x8,%rcx
    69e7:       be 08 00 00 00          mov    $0x8,%esi
    69ec:       48 0f 47 f1             cmova  %rcx,%rsi
    69f0:       48 85 c0                test   %rax,%rax
    69f3:       74 17                   je     6a0c <scratch::reserve+0x5c>
    69f5:       48 8b 0b                mov    (%rbx),%rcx
    69f8:       48 89 0c 24             mov    %rcx,(%rsp)
    69fc:       48 89 44 24 08          mov    %rax,0x8(%rsp)
    6a01:       48 c7 44 24 10 01 00    movq   $0x1,0x10(%rsp)
    6a08:       00 00
    6a0a:       eb 08                   jmp    6a14 <scratch::reserve+0x64>
    6a0c:       48 c7 04 24 00 00 00    movq   $0x0,(%rsp)
    6a13:       00
    6a14:       48 8d 7c 24 18          lea    0x18(%rsp),%rdi
    6a19:       48 89 e1                mov    %rsp,%rcx
    6a1c:       ba 01 00 00 00          mov    $0x1,%edx
    6a21:       e8 9a fe ff ff          call   68c0 <alloc::raw_vec::finish_grow>
    6a26:       48 8b 7c 24 20          mov    0x20(%rsp),%rdi
    6a2b:       48 8b 74 24 28          mov    0x28(%rsp),%rsi
    6a30:       48 83 7c 24 18 01       cmpq   $0x1,0x18(%rsp)
    6a36:       74 0d                   je     6a45 <scratch::reserve+0x95>
    6a38:       48 89 3b                mov    %rdi,(%rbx)
    6a3b:       48 89 73 08             mov    %rsi,0x8(%rbx)
    6a3f:       48 83 c4 30             add    $0x30,%rsp
    6a43:       5b                      pop    %rbx
    6a44:       c3                      ret
    6a45:       48 85 f6                test   %rsi,%rsi
    6a48:       75 08                   jne    6a52 <scratch::reserve+0xa2>
    6a4a:       ff 15 38 c4 03 00       call   *0x3c438(%rip)        # 42e88 <_GLOBAL_OFFSET_TABLE_+0x490>
    6a50:       0f 0b                   ud2
    6a52:       ff 15 f0 c4 03 00       call   *0x3c4f0(%rip)        # 42f48 <_GLOBAL_OFFSET_TABLE_+0x550>
    6a58:       0f 0b                   ud2
    6a5a:       66 0f 1f 44 00 00       nopw   0x0(%rax,%rax,1)
```

After:
```asm
0000000000006910 <scratch::reserve>:
    6910:       48 8b 47 08             mov    0x8(%rdi),%rax
    6914:       48 8b 77 10             mov    0x10(%rdi),%rsi
    6918:       48 29 f0                sub    %rsi,%rax
    691b:       48 3d d1 04 00 00       cmp    $0x4d1,%rax
    6921:       77 05                   ja     6928 <scratch::reserve+0x18>
    6923:       e9 e8 fe ff ff          jmp    6810 <alloc::raw_vec::RawVec<T,A>::reserve::do_reserve_and_handle>
    6928:       c3                      ret
    6929:       0f 1f 80 00 00 00 00    nopl   0x0(%rax)
```