Added project-specific Zed IDE settings
This repository currently has project-specific VS Code IDE settings in `.vscode` and `compiler/rustc_codegen_cranelift/.vscode`. Now there are equivalent project-specific Zed IDE settings alongside those.
This fixes `rust-analyzer` not being able to properly handle this project.
Note that:
1. The contents of `src/tools/rust-analyzer/.vscode` could not be translated to Zed, as they aren't basic IDE settings.
2. One of the VS Code settings in `.vscode` has no corresponding setting in Zed, and so this has been noted like this:
```json
"_settings_only_in_vs_code_not_yet_in_zed": {
"git.detectSubmodulesLimit": 20
},
```
Add profiling of bootstrap commands using Chrome events
Since we now have support for tracing in bootstrap, and the execution of most commands is centralized within a few functions, it's quite trivial to also trace command execution, and visualize it using the Chrome profiler. This can be helpful both to profile what takes time in bootstrap and also to get a visual idea of what happens in a given bootstrap invocation (since the execution of external commands is usually the most interesting thing).
This is how it looks:

I first tried to use [tracing-flame](https://github.com/tokio-rs/tracing/tree/master/tracing-flame), but the output wasn't very useful, because the event/stackframe names were bootstrap code locations, instead of the command contents.
r? ``@jieyouxu``
valtree performance tuning
Summary: This PR makes type checking of code with many type-level constants faster.
After https://github.com/rust-lang/rust/pull/136180 was merged, we observed a small perf regression (https://github.com/rust-lang/rust/pull/136318#issuecomment-2635562821). This happened because that PR introduced additional copies in the fast reject code path for consts, which is very hot for certain crates: 6c1d960d88/compiler/rustc_type_ir/src/fast_reject.rs (L486-L487)
This PR improves the performance again by properly interning the valtrees so that copying and comparing them becomes faster. This will become especially useful with `feature(adt_const_params)`, so the fast reject code doesn't have to do a deep compare of the valtrees.
Note that we can't just compare the interned consts themselves in the fast reject, because sometimes `'static` lifetimes in the type are be replaced with inference variables (due to canonicalization) on one side but not the other.
A less invasive alternative that I considered is simply avoiding copies introduced by https://github.com/rust-lang/rust/pull/136180 and comparing the valtrees it in-place (see commit: 9e91e50ac5 / perf results: https://github.com/rust-lang/rust/pull/136593#issuecomment-2642303245), however that was still measurably slower than interning.
There are some minor regressions in secondary benchmarks: These happen due to changes in memory allocations and seem acceptable to me. The crates that make heavy use of valtrees show no significant changes in memory usage.
Parallel-compiler-related cleanup
Parallel-compiler-related cleanup
I carefully split changes into commits. Commit messages are self-explanatory. Squashing is not recommended.
cc "Parallel Rustc Front-end" https://github.com/rust-lang/rust/issues/113349
r? SparrowLii
``@rustbot`` label: +WG-compiler-parallel
dev-guide: Link to `t-lang` procedures for new features
I was confused in https://github.com/rust-lang/rust/pull/136867, because while I did remember that such a procedure existed, but I couldn't seem to find it in the dev guide.
Improve documentation when adding a new target
https://github.com/rust-lang/rust/pull/133631#issuecomment-2607877936 shows that it can be a bit difficult process-wise to add a new target.
I've added a bit of text to the docs, suggesting that users add the target defintion/spec first, and later work on `std` support.
I also found that we have two places where we document how to add a new target. I've linked these for now, but they should probably be merged somehow in the future.
`@rustbot` label A-docs
r? compiler
CC `@workingjubilee` who's worked a lot on target specs IIRC.
Simplify and consolidate the way we handle construct `OutlivesEnvironment` for lexical region resolution
This is best reviewed commit-by-commit. I tried to consolidate the API for lexical region resolution *first*, then change the API when it was finally behind a single surface.
r? lcnr or reassign