Start moving wf checking away from HIR #142030

oli-obk · 2025-06-04T15:10:05Z

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 · 2025-06-04T15:10:10Z

r? @SparrowLii

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oli-obk · 2025-06-04T15:10:18Z

@bors2 try @rust-timer queue

rust-bors · 2025-06-04T15:10:22Z

⌛ Trying commit e38ae45 with merge 2a676f2…

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

Start moving wf checking away from HIR 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

rust-bors · 2025-06-04T17:38:54Z

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

rust-timer · 2025-06-04T21:19:25Z

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 · 2025-06-05T06:58:34Z

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 · 2025-06-05T08:05:05Z

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 · 2025-06-06T16:18:18Z

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

oli-obk · 2025-06-26T07:58:30Z

@bors try @rust-timer queue

bors · 2025-06-26T07:59:43Z

⌛ Trying commit d587a01 with merge 128972a...

Start moving wf checking away from HIR 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

bors · 2025-06-26T10:34:07Z

☀️ Try build successful - checks-actions
Build commit: 128972a (128972a21f1ffb28749258e5566c02e2ef7a3e49)

rust-timer · 2025-06-26T18:13:38Z

Finished benchmarking commit (128972a): comparison URL.

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

Benchmarking this pull request means it may be perf-sensitive – we'll automatically label it not fit for rolling up. You can override this, but we strongly advise not to, due to possible changes in compiler perf.

Next Steps: If you can justify the regressions found in this try perf run, please do so in sufficient writing along with @rustbot label: +perf-regression-triaged. If not, please fix the regressions and do another perf run. If its results are neutral or positive, the label will be automatically removed.

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

Instruction count

Our most reliable metric. Used to determine the overall result above. However, even this metric can be noisy.

	mean	range	count
Regressions ❌ (primary)	-	-	0
Regressions ❌ (secondary)	0.4%	[0.3%, 0.6%]	3
Improvements ✅ (primary)	-0.4%	[-0.4%, -0.2%]	5
Improvements ✅ (secondary)	-0.4%	[-1.0%, -0.2%]	10
All ❌✅ (primary)	-0.4%	[-0.4%, -0.2%]	5

Max RSS (memory usage)

Results (primary 7.3%, secondary 4.5%)

A less reliable metric. May be of interest, but not used to determine the overall result above.

	mean	range	count
Regressions ❌ (primary)	7.3%	[7.3%, 7.3%]	1
Regressions ❌ (secondary)	4.5%	[4.0%, 5.1%]	2
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	7.3%	[7.3%, 7.3%]	1

Cycles

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

Binary size

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

Bootstrap: 692.088s -> 689.03s (-0.44%)
Artifact size: 372.11 MiB -> 372.07 MiB (-0.01%)

compiler-errors · 2025-07-01T14:56:03Z

compiler/rustc_hir_analysis/src/collect.rs

-}
-
-fn lower_variant_ctor(tcx: TyCtxt<'_>, def_id: LocalDefId) {
+pub(super) fn lower_variant_ctor(tcx: TyCtxt<'_>, def_id: LocalDefId) {


As a follow-up, it would be nice to rename these from lower_* to check_* or something.

compiler-errors · 2025-07-01T14:58:21Z

@bors r+ rollup=never

bors · 2025-07-01T14:58:24Z

📌 Commit 422eea2 has been approved by compiler-errors

It is now in the queue for this repository.

bors · 2025-07-01T15:00:03Z

⌛ Testing commit 422eea2 with merge 4e97337...

bors · 2025-07-01T18:08:44Z

☀️ Test successful - checks-actions
Approved by: compiler-errors
Pushing 4e97337 to master...

github-actions · 2025-07-01T18:12:03Z

What is this?

This is an experimental post-merge analysis report that shows differences in test outcomes between the merged PR and its parent PR.

Comparing 076a0a2 (parent) -> 4e97337 (this PR)

Test differences

No test diffs found

Test dashboard

Run

cargo run --manifest-path src/ci/citool/Cargo.toml -- \
    test-dashboard 4e973370053a5fe87ee96d43c506623e9bd1eb9d --output-dir test-dashboard

And then open test-dashboard/index.html in your browser to see an overview of all executed tests.

Job duration changes

x86_64-apple-2: 7543.2s -> 4792.7s (-36.5%)
dist-x86_64-apple: 7877.4s -> 10653.6s (35.2%)
x86_64-apple-1: 9079.6s -> 7464.4s (-17.8%)
dist-apple-various: 8235.0s -> 7210.4s (-12.4%)
aarch64-gnu: 7205.1s -> 6476.3s (-10.1%)
i686-gnu-1: 8191.8s -> 7501.9s (-8.4%)
dist-various-1: 3894.8s -> 4191.9s (7.6%)
mingw-check-1: 1769.9s -> 1902.3s (7.5%)
mingw-check-2: 1980.0s -> 2111.2s (6.6%)
dist-loongarch64-musl: 4934.2s -> 5198.5s (5.4%)

How to interpret the job duration changes?

Job durations can vary a lot, based on the actual runner instance
that executed the job, system noise, invalidated caches, etc. The table above is provided
mostly for t-infra members, for simpler debugging of potential CI slow-downs.

rust-timer · 2025-07-01T19:21:03Z

Finished benchmarking commit (4e97337): comparison URL.

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

Our benchmarks found a performance regression caused by this PR.
This might be an actual regression, but it can also be just noise.

Next Steps:

If the regression was expected or you think it can be justified,
please write a comment with sufficient written justification, and add
@rustbot label: +perf-regression-triaged to it, to mark the regression as triaged.
If you think that you know of a way to resolve the regression, try to create
a new PR with a fix for the regression.
If you do not understand the regression or you think that it is just noise,
you can ask the @rust-lang/wg-compiler-performance working group for help (members of this group
were already notified of this PR).

@rustbot label: +perf-regression
cc @rust-lang/wg-compiler-performance

Instruction count

Our most reliable metric. Used to determine the overall result above. However, even this metric can be noisy.

	mean	range	count
Regressions ❌ (primary)	-	-	0
Regressions ❌ (secondary)	0.4%	[0.3%, 0.6%]	3
Improvements ✅ (primary)	-0.4%	[-0.4%, -0.4%]	2
Improvements ✅ (secondary)	-0.5%	[-1.1%, -0.3%]	8
All ❌✅ (primary)	-0.4%	[-0.4%, -0.4%]	2

Max RSS (memory usage)

Results (primary 0.4%, secondary -0.2%)

A less reliable metric. May be of interest, but not used to determine the overall result above.

	mean	range	count
Regressions ❌ (primary)	2.0%	[1.3%, 2.6%]	2
Regressions ❌ (secondary)	2.0%	[1.3%, 2.7%]	2
Improvements ✅ (primary)	-2.6%	[-2.6%, -2.6%]	1
Improvements ✅ (secondary)	-4.7%	[-4.7%, -4.7%]	1
All ❌✅ (primary)	0.4%	[-2.6%, 2.6%]	3

Cycles

Results (primary -0.9%, secondary -0.9%)

A less reliable metric. May be of interest, but not used to determine the overall result above.

	mean	range	count
Regressions ❌ (primary)	1.8%	[1.4%, 2.2%]	2
Regressions ❌ (secondary)	3.5%	[3.5%, 3.5%]	1
Improvements ✅ (primary)	-1.8%	[-2.6%, -1.1%]	6
Improvements ✅ (secondary)	-1.6%	[-2.4%, -0.9%]	6
All ❌✅ (primary)	-0.9%	[-2.6%, 2.2%]	8

Binary size

Results (secondary -0.0%)

A less reliable metric. May be of interest, but not used to determine the overall result above.

	mean	range	count
Regressions ❌ (primary)	-	-	0
Regressions ❌ (secondary)	-	-	0
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-0.0%	[-0.0%, -0.0%]	1
All ❌✅ (primary)	-	-	0

Bootstrap: 461.796s -> 461.855s (0.01%)
Artifact size: 372.30 MiB -> 372.23 MiB (-0.02%)

oli-obk · 2025-07-01T21:24:51Z

Improvements outweigh the regressions. And measured time is improved on the only benchmark that regressed instructions

@rustbot label: +perf-regression-triaged

rustbot assigned SparrowLii Jun 4, 2025

rustbot added S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. T-compiler Relevant to the compiler team, which will review and decide on the PR/issue. WG-trait-system-refactor The Rustc Trait System Refactor Initiative (-Znext-solver) labels Jun 4, 2025

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rustbot added perf-regression Performance regression. and removed S-waiting-on-perf Status: Waiting on a perf run to be completed. labels Jun 4, 2025

oli-obk force-pushed the wfck-less-hir branch from e38ae45 to 3dfd50d Compare June 5, 2025 08:06

oli-obk force-pushed the wfck-less-hir branch from 3dfd50d to d587a01 Compare June 26, 2025 07:58

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oli-obk added 11 commits June 30, 2025 08:45

Check variances in the non-hir wfchecker

ee8fa4e

Use predicate spans instead of whole item spans

28f023c

Move lazy type alias checks to non-hir-wfck

632a921

Merge lower_item into check_item_type

cb158c2

Merge lower_trait_item and lower_impl_item into check_item_type

5940109

Avoid eagerly loading the hir fn sig

70215df

Avoid looking at HIR for trait and impl items

6166cd6

Stop requiring HIR for trait item wf checks

38ef94a

Stop requiring HIR for impl item wf checks

5ddae35

Avoid some eager uses of HIR spans

65aac24

Don't run hir wfcheck if ty wfcheck handled everything

422eea2

oli-obk force-pushed the wfck-less-hir branch from 24b0e1d to 422eea2 Compare June 30, 2025 08:47

compiler-errors approved these changes Jul 1, 2025

View reviewed changes

bors added S-waiting-on-bors Status: Waiting on bors to run and complete tests. Bors will change the label on completion. and removed S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. labels Jul 1, 2025

bors added the merged-by-bors This PR was explicitly merged by bors. label Jul 1, 2025

bors merged commit 4e97337 into rust-lang:master Jul 1, 2025
11 checks passed

rustbot added this to the 1.90.0 milestone Jul 1, 2025

This was referenced Jul 1, 2025

[perf] test MCP510 #113382

Draft

Try use tcx.ensure_ok for some predicates_of queries. #139256

Draft

oli-obk deleted the wfck-less-hir branch July 1, 2025 18:44

bors mentioned this pull request Jul 1, 2025

Simplify polonius location-sensitive analysis #143093

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rustbot added the perf-regression-triaged The performance regression has been triaged. label Jul 1, 2025

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Start moving wf checking away from HIR #142030

Start moving wf checking away from HIR #142030

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Start moving wf checking away from HIR #142030

Start moving wf checking away from HIR #142030

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

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

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Test differences

Job duration changes

rust-timer commented Jul 1, 2025

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

oli-obk commented Jul 1, 2025