Add tracing to InterpCx::fn_abi_of_instance/fn_abi_of_fn_ptr

[Stypox]

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 #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 #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

Analysis of the places where layout_of is called

I did some analysis for #142721 (comment), 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
• 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

[rustbot]

Some changes occurred to the CTFE machinery

cc @RalfJung, @oli-obk, @lcnr

Some changes occurred to the CTFE / Miri interpreter

cc @rust-lang/miri

The Miri subtree was changed

cc @rust-lang/miri

[RalfJung]

Makes sense, thanks!

@bors r+ rollup

[bors]

📌 Commit 14f4700 has been approved by RalfJung

It is now in the queue for this repository.