Sometimes an obligation depends on a later one, so we can't just process them in order like it was done previously.

This is not a problem in our test suite, but there may be ICEs out there and it will definitely be a problem with lazy TAIT.

The issue here is that the logic used to determine which CGU to put the
dead function stubs in doesn't handle cases where a module is never
assigned to a CGU.

The partitioning logic also caused issues in rust-lang#85461 where inline
functions were duplicated into multiple CGUs resulting in duplicate
symbols.

This commit fixes the issue by removing the complex logic used to assign
dead code stubs to CGUs and replaces it with a much simplier model: we
pick one CGU to hold all the dead code stubs. We pick a CGU which has
exported items which increases the likelihood the linker won't throw
away our dead functions and we pick the smallest to minimize the impact
on compilation times for crates with very large CGUs.

Fixes rust-lang#86177
Fixes rust-lang#85718
Fixes rust-lang#79622

Because MIPSr6 has many differences with previous MIPSr2 arch, the previous rlib metadata stripping code in `rustc_codegen_ssa` is only for MIPSr2/r3/r5 (which share the same elf e_flags).
This commit fixed this problem. It makes `rustc_codegen_ssa` happy when compiling rustc for MIPSr6 target or hosts.

It's already a (fat) reference.
Double referencing it creates lifetime issues for its methods that want to return iterators.

As discussed in
rust-lang#92142 (comment),
tests that contain multiple files order their results differently on
Windows and Linux which the test runner currently can't handle
correctly. For now, ignore the "bin" part of the test and only include
the unused library dependency which is what the test really cares about
anyway.

Make rlib metadata strip works with MIPSr6 architecture

Because MIPSr6 has many differences with previous MIPSr2 arch, the previous rlib metadata stripping code in `rustc_codegen_ssa` is only for MIPSr2/r3/r5 (which share the same elf e_flags).

This commit fixed this problem. It makes `rustc_codegen_ssa` happy when compiling rustc for MIPSr6 target or hosts.

e_flags REF: https://github.com/llvm/llvm-project/blob/e356027016c6365b3d8924f54c33e2c63d931492/llvm/include/llvm/BinaryFormat/ELF.h#L562

… r=GuillaumeGomez

rustdoc: do not emit tuple variant fields if none are documented

Fixes rust-lang#90824.

Before:

![2021-12-15T22:26:41](https://user-images.githubusercontent.com/1372438/146302871-4d265433-b9aa-4e53-adfb-e7cb92107180.png)

After:

![2021-12-15T22:27:01](https://user-images.githubusercontent.com/1372438/146302872-e39eda3d-2fb2-4fb9-aae7-2008e4e1b4dd.png)

Add `std::error::Report` type

This is a continuation of rust-lang#90174, split into a separate PR since I cannot push to ```````@seanchen1991``````` 's fork

…he_fold, r=nikomatsakis

Welcome opaque types into the fold

r? ```@nikomatsakis``` because idk who else to bug on the type_op changes

The commits have explanations in them. The TLDR is that

* 5c46002 stops the "recurse and replace" scheme that replaces opaque types with their canonical inference var by just doing that ahead of time
* bdeeb07 does not affect anything on master afaict, but since opaque types generate obligations when instantiated, and lazy TAIT instantiates opaque types *everywhere*, we need to properly handle obligations here instead of just hoping no problematic obligations ever come up.

…ioning, r=tmandry

[code coverage] Fix missing dead code in modules that are never called

The issue here is that the logic used to determine which CGU to put the dead function stubs in doesn't handle cases where a module is never assigned to a CGU (which is what happens when all of the code in the module is dead).

The partitioning logic also caused issues in rust-lang#85461 where inline functions were duplicated into multiple CGUs resulting in duplicate symbols.

This commit fixes the issue by removing the complex logic used to assign dead code stubs to CGUs and replaces it with a much simpler model: we pick one CGU to hold all the dead code stubs. We pick a CGU which has exported items which increases the likelihood the linker won't throw away our dead functions and we pick the smallest to minimize the impact on compilation times for crates with very large CGUs.

Fixes rust-lang#91661
Fixes rust-lang#86177
Fixes rust-lang#85718
Fixes rust-lang#79622

r? ```@tmandry```
cc ```@richkadel```

This PR is not urgent so please don't let it interrupt your holidays! 🎄 🎁

rustc_metadata: Stop passing `CrateMetadataRef` by reference (step 1)

It's already a (fat) reference.
Double referencing it creates lifetime issues for its methods that want to return iterators.

---
Extracted from rust-lang#92245 for a perf run.
The PR changes a lot of symbol names due to function signature changes, so it's hard to do differential profiling, let's spend some machine time instead.

…uillaumeGomez

rustdoc: Preserve rendering of macro_rules matchers when possible

Fixes rust-lang#92331. This approach restores the behavior prior to rust-lang#86282 **if** the matcher token held by the compiler **and** the matcher token found in the source code are identical TokenTrees. Thus rust-lang#86208 remains fixed, but without regressing formatting for the vast majority of macros which are not macro-generated.

Update cargo

6 commits in 358e79fe56fe374649275ca7aebaafd57ade0e8d..06b9d31743210b788b130c8a484c2838afa6fc27
2022-01-04 18:39:45 +0000 to 2022-01-11 23:47:29 +0000
- Port cargo to clap3 (rust-lang/cargo#10265)
- feat: support rustflags per profile (rust-lang/cargo#10217)
- Make bors ignore the PR template so it doesn't end up in merge messages (rust-lang/cargo#10267)
- Be resilient to most IO error and filesystem loop while walking dirs (rust-lang/cargo#10214)
- Remove the option to disable pipelining (rust-lang/cargo#10258)
- Always ask rustc for messages about artifacts, and always process them (rust-lang/cargo#10255)

Update RELEASES for 1.58.

From what I can tell:

* `NonZero{unsigned}::is_power_of_two` was stabilized in 1.59: rust-lang#91301
* `MaybeUninit` const was added in 1.59: rust-lang#90896