Fixes #88701

Mmap the incremental data instead of reading it.

Instead of reading the full incremental state using `fs::read_file`, we memmap it using a private read-only file-backed map.
This allows the system to reclaim any memory we are not using, while ensuring we are not polluted by
outside modifications to the file.

Suggested in rust-lang/rust#83036 (comment) by `@bjorn3`

BTreeMap/BTreeSet::from_iter: use bulk building to improve the performance

Bulk building is a common technique to increase the performance of building a fresh btree map. Instead of inserting items one-by-one, we sort all the items beforehand then create the BtreeMap in bulk.

Benchmark
```
./x.py bench library/alloc --test-args btree::map::from_iter
```

* Before
```
test btree::map::from_iter_rand_100                      ... bench:       3,694 ns/iter (+/- 840)
test btree::map::from_iter_rand_10_000                   ... bench:   1,033,446 ns/iter (+/- 192,950)
test btree::map::from_iter_seq_100                       ... bench:       5,689 ns/iter (+/- 1,259)
test btree::map::from_iter_seq_10_000                    ... bench:     861,033 ns/iter (+/- 118,815)
```

* After
```
test btree::map::from_iter_rand_100                      ... bench:       3,033 ns/iter (+/- 707)
test btree::map::from_iter_rand_10_000                   ... bench:     775,958 ns/iter (+/- 105,152)
test btree::map::from_iter_seq_100                       ... bench:       2,969 ns/iter (+/- 336)
test btree::map::from_iter_seq_10_000                    ... bench:     258,292 ns/iter (+/- 29,364)
```

Move `confused_type_with_std_module` to `ResolverOutputs`

This eliminates untracked global state from `Session`.

Adapts clippy for fe1a7f7

Note that this incorrectly suggests a shared borrow,
but at least we know it's happening.

Add `TAU` to `approx_constant`

changelog: [`approx_constant`]: Add `TAU`

…r=petrochenkov

Fix handling of +whole-archive native link modifier.

This PR fixes a bug in `add_upstream_native_libraries` that led to the `+whole-archive` modifier being ignored when linking in native libs.

~~Note that the PR does not address the situation when `+whole-archive` is combined with `+bundle`.~~
`@wesleywiser's` commit adds validation code that turns combining `+whole-archive` with `+bundle` into an error.

Fixes rust-lang/rust#88085.

r? `@petrochenkov`
cc `@wesleywiser` `@gcoakes`

Use index newtyping for TyVid

This is useful for using TyVid in types like VecGraph, and just otherwise seems like a small win.

Bump RLS submodule

r? `@Mark-Simulacrum`

These were deleted in https://reviews.llvm.org/D108614, and in C++ I
definitely see the argument for their removal. I didn't try and
propagate the changes up into higher layers of rustc in this change
because my initial goal was to get rustc working against LLVM HEAD
promptly, but I'm happy to follow up with some refactoring to make the
API on the Rust side match the LLVM API more directly (though the way
the enum works in Rust makes the API less scary IMO).

r? @nagisa cc @nikic

Otherwise we're kind of reimplementing the inverse of the well-named
methods, and that's not a direction we want to go.

* Draft of initial RMC documentation

* revisions in response to feedback

Add -Z panic-in-drop={unwind,abort} command-line option

This PR changes `Drop` to abort if an unwinding panic attempts to escape it, making the process abort instead. This has several benefits:
- The current behavior when unwinding out of `Drop` is very unintuitive and easy to miss: unwinding continues, but the remaining drops in scope are simply leaked.
- A lot of unsafe code doesn't expect drops to unwind, which can lead to unsoundness:
  - servo/rust-smallvec#14
  - bluss/arrayvec#3
- There is a code size and compilation time cost to this: LLVM needs to generate extra landing pads out of all calls in a drop implementation. This can compound when functions are inlined since unwinding will then continue on to process drops in the callee, which can itself unwind, etc.
  - Initial measurements show a 3% size reduction and up to 10% compilation time reduction on some crates (`syn`).

One thing to note about `-Z panic-in-drop=abort` is that *all* crates must be built with this option for it to be sound since it makes the compiler assume that dropping `Box<dyn Any>` will never unwind.

cc rust-lang/lang-team#97

Introduce NullOp::AlignOf

This PR introduces `Rvalue::NullaryOp(NullOp::AlignOf, ty)`, which will be lowered from `align_of`, similar to `size_of` lowering to `Rvalue::NullaryOp(NullOp::SizeOf, ty)`.

The changes are originally part of #88700 but since it's not dependent on other changes and could have performance impact on its own, it's separated into its own PR.

Update Clippy dependencies without patch versions

Trial run for rust-lang/rust-clippy#7606

ARMv6K Nintendo 3DS Tier 3 target added

Addition of the target specifications to build .elf files for Nintendo 3DS (ARMv6K, Horizon). Requires devkitARM 3DS toolkit for system libraries and arm-none-eabi-gcc linker.

…eGomez

Allow missing code examples in trait impls.

Excludes Trait implementations from the items that need to have doc code examples when using the `rustdoc::missing_doc_code_examples` lint.

For details see #88741

fixes #88741

r? `@jyn514`

Update cargo

6 commits in 18751dd3f238d94d384a7fe967abfac06cbfe0b9..e515c3277bf0681bfc79a9e763861bfe26bb05db
2021-09-01 14:26:00 +0000 to 2021-09-08 14:32:15 +0000
- Remove log output that may leak tokens (rust-lang/cargo#9873)
- rev = "refs/pull/𑑛/head" (rust-lang/cargo#9859)
- Update suggestion message on bad project name error (rust-lang/cargo#9877)
- clarify what goes into "*-sys" crates (rust-lang/cargo#9871)
- Improve error message when unable to initialize git index repo (rust-lang/cargo#9869)
- Use serde_json to generate cargo_vcs_info.json (rust-lang/cargo#9865)

* Introduce the first section of the RMC tutorial

* add license boilerplate, correct typos

* fix formatting

Use smaller spans for some structured suggestions

Use more accurate suggestion spans for

* argument parse error
* fully qualified path
* missing code block type
* numeric casts

 * Add test for jump-to-def links background color

Add links for primitives in "jump to definition" feature

Follow-up of #84176.

I created a function `primitive_from_str` which is code that was originally in `collect_intra_doc_links::resolve_primitive` to prevent code duplication.

I also created the `primitive_link_url` function which is somewhat similar to `primitive_link` but too much different to merge both of them.

r? ``@jyn514``

…olnay

Make `UnsafeCell::get_mut` const

Fix duplicate bounds for const_trait_impl

Fixes #88383.

Compare the constness of the candidates before winnowing and removing a `~const` `BoundCandidate`.

interpreter PointerArithmetic: use new Size helper methods

…melid

Fix jump def background

Fixes #88870.

I somehow badly wrote the color in #88111.

r? ``@camelid``

Improve error message for missing trait in trait impl

Fixes #88818. For the following example:
```rust
struct S { }
impl for S { }
```
the current output is:
```
error: missing trait in a trait impl
 --> t1.rs:2:5
  |
2 | impl for S { }
  |     ^
```
With my changes, I get:
```
error: missing trait in a trait impl
 --> t1.rs:2:5
  |
2 | impl for S { }
  |     ^
  |
help: add a trait here
  |
2 | impl Trait for S { }
  |      +++++
help: for an inherent impl, drop this `for`
  |
2 - impl for S { }
2 + impl S { }
  |
```

Reduce possibility of flaky tests

As asked in rust-lang/rust#88885.

r? ``@camelid``

Enum should prefer discriminant zero for niche

Given an enum with unassigned zero-discriminant, rust should prefer it for niche selection.
Zero as discriminant for `Option<Enum>` makes it possible for LLVM to optimize resulting asm.

- Eliminate branch when expected value coincides.
- Use smaller instruction `test eax, eax` instead of `cmp eax, ?`
- Possible interaction with zeroed memory?

Example:
```rust

pub enum Size {
    One = 1,
    Two = 2,
    Three = 3,
}

pub fn handle(x: Option<Size>) -> u8 {
    match x {
        None => {0}
        Some(size) => {size as u8}
    }
}
```
In this case discriminant zero is available as a niche.

Above example on nightly:
```asm
 mov     eax, edi
 cmp     al, 4
 jne     .LBB0_2
 xor     eax, eax
.LBB0_2:
 ret
```

PR:
```asm
 mov     eax, edi
 ret
```

I created this PR because I had a performance regression when I tried to use an enum to represent legal grapheme byte-length for utf8.

Using an enum instead of `NonZeroU8` [here](https://github.com/bonega/yore/blob/d683304f5dfe2e99f769e6ab8adf8d60a0d1d9b3/src/internal/decoder_incomplete.rs#L90)
resulted in a performance regression of about 5%.
I consider this to be a somewhat realistic benchmark.

Thanks to `@ogoffart` for pointing me in the right direction!

Edit: Updated description

Rollup of 7 pull requests

Successful merges:

 - #88033 (Add links for primitives in "jump to definition" feature)
 - #88722 (Make `UnsafeCell::get_mut` const)
 - #88851 (Fix duplicate bounds for const_trait_impl)
 - #88859 (interpreter PointerArithmetic: use new Size helper methods)
 - #88885 (Fix jump def background)
 - #88894 (Improve error message for missing trait in trait impl)
 - #88896 (Reduce possibility of flaky tests)

Failed merges:

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

Rename "--display-warnings" to "--display-doctest-warnings"

Fixes #41574.

cc `@ollie27`
r? `@kinnison`

Conflicts:
    .github/workflows/ci.yml

A new NullOp was added in order to retrieve the minimum alignment
of a type in the rust compiler.

This change adds code generation for this operator in the gotoc codegen.