Add tracing to various miscellaneous functions

[Stypox]

This PR adds tracing to:

• ty.fn_sig(). There is only one place where fn_sig is called for real within rustc_const_eval. There are three other places where it's called, but one is inside ConstCx::fn_sig (which does not seem to be used anywhere), another is under if cfg!(debug_assertions), and the last is within call_main and thus gets called only once.
• the two possible things find_mir_or_eval_fn can do: "emulate_foreign_item" and "load_mir"
• all calls to Const.eval() within the Miri or the rustc_const_eval codebase.
• a separate commit also fixes the style of some tracing macros

Those are all quite long-lived operations, that in total make up for 6-7% of the total time spent in the program. I found out about them by looking for long periods of time that were previously not traced at all, using this SQL query in ui.perfetto.dev:

with ordered as (select s1.*, row_number() over (order bys1.ts) as rn from slices as s1 wheres1.parent_id is nullands1.dur>0ands1.name!="frame"ands1.name!="step"ands1.name!="backtrace") selecta.ts+a.duras ts, b.ts-a.ts-a.duras dur, a.id, a.track_id, a.category, a.depth, a.stack_id, a.parent_stack_id, a.parent_id, a.arg_set_id, a.thread_ts, a.thread_instruction_count, a.thread_instruction_delta, a.cat, a.slice_id, "empty"as name from ordered as a inner join ordered as b ona.rn=b.rn-1/*where b.ts-a.ts-a.dur > 5000*/order byb.ts-a.ts-a.durdesc

How the table was obtained

The above image was obtained in ui.perfetto.dev with the following SQL query after obtaining a trace file by running Miri on the following Rust code with n=100.

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

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

r? @RalfJung

[rustbot]

The Miri subtree was changed

cc @rust-lang/miri

Some changes occurred to the CTFE / Miri interpreter

cc @rust-lang/miri

Some changes occurred to the CTFE machinery

cc @RalfJung, @oli-obk, @lcnr

[Stypox]

Thanks for the review, I addressed the comments

[RalfJung]

LGTM. :) Please squash this into a single commit.
@rustbot author

[rustbot]

Reminder, once the PR becomes ready for a review, use @rustbot ready.

[Stypox]

@rustbot ready

[RalfJung]

@bors r+ rollup

[bors]

📌 Commit dc72692 has been approved by RalfJung

It is now in the queue for this repository.