Start moving wf checking away from HIR

[oli-obk]

I'm trying to only access the HIR in the error path. My hope is that once we move significant portions of wfcheck off HIR that incremental will be able to cache wfcheck queries significantly better.

I think I am reaching a blocker because we normally need to provide good spans to ObligationCause, so that the trait solver can report good errors. In some cases I have been able to use bad spans and improve them depending on the ObligationCauseCode (by loading HIR in the case where we actually want to error). To scale that further we'll likely need to remove spans from the ObligationCause entirely (leaving it to some variants of ObligationCauseCode to have a span when they can't recompute the information later). Unsure this is the right approach, but we've already been using it. I will create an MCP about it, but that should not affect this PR, which is fairly limited in where it does those kind of tricks.

Especially b862d88 is interesting here, because I think it improves spans in all cases

[rustbot]

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[oli-obk]

@bors2 try @rust-timer queue

[rust-bors]

⌛ Trying commit e38ae45 with merge 2a676f2…

To cancel the try build, run the command @bors2 try cancel.

[rust-bors]

☀️ Try build successful (CI)
Build commit: 2a676f2 (2a676f231127fb1728da0a95c8deb1e1fb8bf0eb)

[rust-timer]

Finished benchmarking commit (2a676f2): comparison URL.

Overall result: ❌✅ regressions and improvements - please read the text below

Benchmarking this pull request likely means that it is perf-sensitive, so we're automatically marking it as not fit for rolling up. While you can manually mark this PR as fit for rollup, we strongly recommend not doing so since this PR may lead to changes in compiler perf.

Next Steps: If you can justify the regressions found in this try perf run, please indicate this with @rustbot label: +perf-regression-triaged along with sufficient written justification. If you cannot justify the regressions please fix the regressions and do another perf run. If the next run shows neutral or positive results, the label will be automatically removed.

@bors rollup=never
@rustbot label: -S-waiting-on-perf +perf-regression

Instruction count

This is the most reliable metric that we have; it was used to determine the overall result at the top of this comment. However, even this metric can sometimes exhibit noise.

	mean	range	count
Regressions ❌ (primary)	-	-	0
Regressions ❌ (secondary)	0.2%	[0.1%, 0.5%]	7
Improvements ✅ (primary)	-0.4%	[-0.4%, -0.4%]	2
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	-0.4%	[-0.4%, -0.4%]	2

Max RSS (memory usage)

Results (primary -3.0%, secondary 0.3%)

This is a less reliable metric that may be of interest but was not used to determine the overall result at the top of this comment.

	mean	range	count
Regressions ❌ (primary)	1.6%	[1.5%, 1.7%]	2
Regressions ❌ (secondary)	2.0%	[1.2%, 3.9%]	8
Improvements ✅ (primary)	-7.6%	[-10.2%, -5.1%]	2
Improvements ✅ (secondary)	-2.3%	[-2.9%, -1.8%]	5
All ❌✅ (primary)	-3.0%	[-10.2%, 1.7%]	4

Cycles

Results (primary 1.5%)

This is a less reliable metric that may be of interest but was not used to determine the overall result at the top of this comment.

	mean	range	count
Regressions ❌ (primary)	1.5%	[1.5%, 1.5%]	1
Regressions ❌ (secondary)	-	-	0
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	1.5%	[1.5%, 1.5%]	1

Binary size

This benchmark run did not return any relevant results for this metric.

Bootstrap: 749.479s -> 749.524s (0.01%)
Artifact size: 371.89 MiB -> 371.96 MiB (0.02%)

[oli-obk]

Improvements are real, fewer dep graph edges to encode

Regressions are real, a mix of improvements and regressions across multiple queries. I'll do some local cache grinding to see what's going on

[oli-obk]

The regression is due to some extra query system things happening:

 2,302,905  ???:<rustc_middle::dep_graph::DepsType as rustc_query_system::dep_graph::Deps>::read_deps::<<rustc_query_system::dep_graph::graph::DepGraph<rustc_middle::dep_graph::DepsType>>::read_index::{closure
 1,917,000  ???:<hashbrown::raw::RawTable<(rustc_span::def_id::LocalDefId, ())>>::reserve_rehash::<hashbrown::map::make_hasher<rustc_span::def_id::LocalDefId, (), rustc_hash::FxBuildHasher>::{closure

Probably because I'm invoking more queries to avoid looking at HIR. I don't think my work pays off while we still check the HIR on so many items.

[bors]

☔ The latest upstream changes (presumably #142099) made this pull request unmergeable. Please resolve the merge conflicts.