Add tracing to `InterpCx::fn_abi_of_instance/fn_abi_of_fn_ptr`
This PR adds tracing to the `InterpCx::fn_abi_of_instance`/`::fn_abi_of_fn_ptr` functions by shadowing `FnAbiOf`'s trait methods with inherent methods on `InterpCx`, like done in rust-lang/rust#142721. The reason why I am targeting these two functions is because they are used for Miri interpretation, and they make a `layout_of` query down the line without passing through the `layout_of` that was traced in rust-lang/rust#142721.
There are other places where `layout_of` is called without being traced (see the analysis below), but that's because the `Machine` used there is not `MiriMachine` but rather `CompileTimeMachine` which does not implement `enter_trace_span()`. But after discussing with ```````@RalfJung``````` we agreed that the const-eval part should not be traced together with Miri, that's why I am ignoring the other places where `layout_of` is called.
r? ```````@RalfJung```````
<details><summary>Analysis of the places where <code>layout_of</code> is called</summary>
I did some analysis for https://github.com/rust-lang/rust/pull/142721#discussion_r2171494841, and these are all the places where the query `tcx.layout_of` is called (directly or indirectly) outside of a traced `InterpCx::layout_of` while a program is being interpreted by Miri:
```
adjust_for_rust_scalar at ./compiler/rustc_ty_utils/src/abi.rs:302:35
{closure#2} at ./compiler/rustc_ty_utils/src/abi.rs:522:25
eval_body_using_ecx<> at ./compiler/rustc_const_eval/src/const_eval/eval_queries.rs:49:22
{closure#1}<> at ./compiler/rustc_const_eval/src/interpret/operand.rs:851:76
{closure#0}<> at ./compiler/rustc_const_eval/src/interpret/stack.rs:612:18
size_and_align at ./compiler/rustc_middle/src/mir/interpret/mod.rs:387:38
```
I got these by:
- patching rustc with this patch that adds a span to the `layout_of` query which prints the backtrace:
[layout_of_other_places.diff.txt](https://github.com/user-attachments/files/21235523/layout_of_other_places.diff.txt)
- adding this to my bootstrap.toml to have debug symbols inside the Miri binary: `rust.debuginfo-level = "line-tables-only"` and also `build.tool.miri.features = ["tracing"]`
- obtaining a trace file with `MIRI_TRACING=1 ./x.py run miri --stage 1 --warnings warn --args src/tools/miri/tests/pass/hello.rs` (note: maybe using a file different than "src/tools/miri/tests/pass/hello.rs" would lead to more places where layout_of is called?)
- running this query in Perfetto to select all `layout_of` spans that have as a direct parent a span named "frame" (as opposed to the parent being `InterpCx::layout_of`) and extract their backtrace: `select args.string_value from slice left join args on slice.arg_set_id = args.id where slice.name = "tcx.layout_of" and slice.parent_id in (select slice2.id from slice as slice2 where slice2.name = "frame") group by args.string_value`
- exporting the data as `.tsv` and processing that file through this Python script. It finds the first path in the backtraces where "layout" isn't mentioned, which imo is a good heuristic to not consider `layout_of` wrappers/friends as call places, but rather go down the backtrace until an actual call place is reached. [layout_of_other_places.py.txt](https://github.com/user-attachments/files/21235529/layout_of_other_places.py.txt)
</details>
update `cfg_select!` documentation
tracking issue: https://github.com/rust-lang/rust/issues/115585
After rust-lang/rust#143461, and with an eye on a soon(ish) stabilization, I think the docs need some work.
The existing text read more like a motivation for the feature existing to me, so I've tried to now be a bit more descriptive. Still, suggestions are very welcome.
I also added a test for an empty `select! {}` because it's just the sort of thing that might break.
r? ``@traviscross``
Preserve constness in trait objects up to hir ty lowering
r? ``@compiler-errors``
While we don't support `dyn const Trait`, we can at least also inform the user that `const Trait` is only legal for `#[const_trait] trait Trait {}`
Rename `stable_mir` and `rustc_smir`
This PR only renames the two crate names.
There is no doubt that we want to rename `stable_mir` to `rustc_public`, while it hasn't been discussed yet that what the new name for `rustc_smir` should be.
This PR proposes a new name for `rustc_smir`, that is `rustc_public_shim`, since `rustc_smir` now is mostly a proxy to do calls to rustc queries and the public API of rustc that is invoked by the `rustc_public` crate.
However, I don't think that name is good enough. I hope there would be a way better name.
r? `@oli-obk`
Retire hir::*ItemRef.
This information was kept for various places that iterate on HIR to know about trait-items and impl-items.
This PR replaces them by uses of the `associated_items` query that contain pretty much the same information.
This shortens many spans to just `def_span`, which can be easier to read.
make `cfg_select` a builtin macro
tracking issue: https://github.com/rust-lang/rust/issues/115585
This parses mostly the same as the `macro cfg_select` version, except:
1. wrapping in double brackets is no longer supported (or needed): `cfg_select {{ /* ... */ }}` is now rejected.
2. in an expression context, the rhs is no longer wrapped in a block, so that this now works:
```rust
fn main() {
println!(cfg_select! {
unix => { "foo" }
_ => { "bar" }
});
}
```
3. a single wildcard rule is now supported: `cfg_select { _ => 1 }` now works
I've also added an error if none of the rules evaluate to true, and warnings for any arms that follow the `_` wildcard rule.
cc `@traviscross` if I'm missing any feature that should/should not be included
r? `@petrochenkov` for the macro logic details
