Rollup merge of #144727 - Stypox:add-tracing-to-resolve, r=RalfJung

Add tracing to resolve-related functions

Resolve-related functions are not called often but still make up for ~3% of execution time for non-repetitive programs (as seen in the first table below, obtained from running the rust snippet at the bottom with `n=1`). On the other hand, for repetitive programs they become less relevant (I tested the same snippet but with `n=100` and got ~1.5%), and it appears that only `try_resolve` is called more often (see the last two tables).

The first table was obtained by opening the trace file in https://ui.perfetto.dev and running the following query:

```sql
select "TOTAL PROGRAM DURATION" as name, count(*), max(ts + dur) as "sum(dur)", 100.0 as "%", null as "min(dur)", null as "max(dur)", null as "avg(dur)", null as "stddev(dur)" from slices union select "TOTAL OVER ALL SPANS (excluding events)" as name, count(*), sum(dur), cast(cast(sum(dur) as float) / (select max(ts + dur) from slices) * 1000 as int) / 10.0 as "%", min(dur), max(dur), cast(avg(dur) as int) as "avg(dur)", cast(sqrt(avg(dur*dur)-avg(dur)*avg(dur)) as int) as "stddev(dur)" from slices where parent_id is null and name != "frame" and name != "step" and dur > 0 union select name, count(*), sum(dur), cast(cast(sum(dur) as float) / (select max(ts + dur) from slices) * 1000 as int) / 10.0 as "%", min(dur), max(dur), cast(avg(dur) as int) as "avg(dur)", cast(sqrt(avg(dur*dur)-avg(dur)*avg(dur)) as int) as "stddev(dur)" from slices where parent_id is null and name != "frame" and name != "step" group by name order by sum(dur) desc, count(*) desc
```

<img width="1687" height="242" alt="image" src="https://github.com/user-attachments/assets/4d4bd890-869b-40f3-a473-8e4c42b02da4" />

The following two tables show how many `resolve` spans there per subname/subcategory, and how much time is spent in each. The first is for `n=1` and the second for `n=100`. The query that was used is:

```sql
select args.string_value as name, count(*), max(dur), avg(dur), sum(dur) from slices inner join args USING (arg_set_id) where args.key = "args." || slices.name and name = "resolve" group by args.string_value
```

<img width="1688" height="159" alt="image" src="https://github.com/user-attachments/assets/a8749856-c099-492e-a86e-6d67b146af9c" />

<img width="1688" height="159" alt="image" src="https://github.com/user-attachments/assets/ce3ac1b5-5c06-47d9-85a6-9b921aea348e" />

The snippet I tested with Miri to obtain the above traces is:

```rust
fn main() {
    let n: usize = std::env::args().nth(1).unwrap().parse().unwrap();
    let mut v = (0..n).into_iter().collect::<Vec<_>>();
    for i in &mut v {
        *i += 1;
    }
}
```

1 files changed, 5 insertions, 1 deletions

diff --git a/compiler/rustc_const_eval/src/interpret/step.rs b/compiler/rustc_const_eval/src/interpret/step.rs
index 76e470b69dc..f1995b3f132 100644
--- a/compiler/rustc_const_eval/src/interpret/step.rs
+++ b/compiler/rustc_const_eval/src/interpret/step.rs
@@ -560,7 +560,11 @@ impl<'tcx, M: Machine<'tcx>> InterpCx<'tcx, M> {
                     "Async Drop must be expanded or reset to sync in runtime MIR"
                 );
                 let place = self.eval_place(place)?;
-                let instance = Instance::resolve_drop_in_place(*self.tcx, place.layout.ty);
+                let instance = {
+                    let _trace =
+                        enter_trace_span!(M, resolve::resolve_drop_in_place, ty = ?place.layout.ty);
+                    Instance::resolve_drop_in_place(*self.tcx, place.layout.ty)
+                };
                 if let ty::InstanceKind::DropGlue(_, None) = instance.def {
                     // This is the branch we enter if and only if the dropped type has no drop glue
                     // whatsoever. This can happen as a result of monomorphizing a drop of a