Remove `nodes_in_current_session` field and related assertions by Zoxc · Pull Request #154283 · rust-lang/rust

Zoxc · 2026-03-24T00:43:27Z

This removes the nodes_in_current_session field and related assertions. These are enabled if -Z incremental-verify-ich is passed or debug_assertions is on. Historically these have been useful to catch query keys with improper HashStable impls which lead to collisions.

We currently also check for duplicate nodes when loading the dep graph. This check is more complete as it covers the entire dep graph and is enabled by default. It doesn't provide a query key for a collision however. This check is also delayed to the next incremental session.

We also have the verify_query_key_hashes which is also enabled if -Z incremental-verify-ich is passed or debug_assertions is on. This checks for dep node conflicts in each query cache and provides 2 conflicting keys if present.

I think these remaining checks are sufficient and so we can remove nodes_in_current_session.

rustbot · 2026-03-24T00:43:32Z

r? @jdonszelmann

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Zoxc · 2026-03-24T00:44:41Z

cc @nnethercote @Zalathar @zetanumbers

jdonszelmann · 2026-04-02T10:59:36Z

This looks reasonable to me, but I'm no expert on the query system. Going to defer to @nnethercote (or someone else if that's better)

r? @nnethercote

nnethercote

Looks good, just one nit below.

View changes since this review

nnethercote · 2026-04-05T23:55:43Z

    }

-    #[cfg(debug_assertions)]
    fn record_edge(


I'd prefer to keep this entire function cfg(debug_assertions), and then likewise at the call sites. It makes it clearer that it's all debug-only, and avoids the need for the underscores on the parameter names.

I was thinking of just converting this to cfg!.

#[cfg] makes the call sites clearer.

Why?
I basically always prefer if cfg! to #[cfg] when technically possible because it doesn't hide the configured-out code from type checker and other later passes.

Fine, whatever, just do cfg! then.

Should I do it in this PR? I was thinking of making a follow-up PR.

Just do it here, save the trouble of filing a follow-up

nnethercote · 2026-04-13T00:30:36Z

            forbidden_edge,
-            #[cfg(debug_assertions)]
-            value_fingerprints: Lock::new(IndexVec::from_elem_n(None, new_node_count_estimate)),
+            value_fingerprints: Lock::new(if cfg!(debug_assertions) {


View changes since the review

Now we are always doing work that we were only doing in debug builds, because we have fields in the struct that we used to only have in debug builds.

Sorry, I didn't realize that switching to cfg! would cause this. I think this goes too far. I suggest just removing this second commit and going with the original first commit which uses #[cfg(debug_attributes)] within record_edge.

I am tempted to add a DebugOnly type so we can have fields only present with debug_assertions, but still get type checking. That would be useful elsewhere too. Would that be sufficient given that the extra work would optimize away?

Not sure I like that, but it would definitely be a separate PR anyway.

rustbot · 2026-04-21T02:22:38Z

This PR was rebased onto a different main commit. Here's a range-diff highlighting what actually changed.

Rebasing is a normal part of keeping PRs up to date, so no action is needed—this note is just to help reviewers.

nnethercote · 2026-04-22T10:32:15Z

@bors r+ rollup

rust-bors · 2026-04-22T10:32:18Z

📌 Commit 0add85c has been approved by nnethercote

It is now in the queue for this repository.

…uwer Rollup of 10 pull requests Successful merges: - #154794 (Add on_unmatch_args) - #155133 (Document precision considerations of `Duration`-float methods) - #154283 (Remove `nodes_in_current_session` field and related assertions) - #155374 (rustdoc: fix a few spots where emit isn't respected) - #155587 (Immediately feed visibility on DefId creation) - #155622 (c-variadic: `va_arg` fixes ) - #155629 (rustc_public: Add `constness` & `asyncness` in `FnDef`) - #155632 (Some metadata cleanups) - #155639 (BinOpAssign always returns unit) - #155647 (rustc-dev-guide subtree update)

Rollup merge of #154283 - Zoxc:rem-nodes_in_current_session, r=nnethercote Remove `nodes_in_current_session` field and related assertions This removes the `nodes_in_current_session` field and related assertions. These are enabled if `-Z incremental-verify-ich` is passed or `debug_assertions` is on. Historically these have been useful to catch query keys with improper `HashStable` impls which lead to collisions. We currently also check for duplicate nodes when loading the dep graph. This check is more complete as it covers the entire dep graph and is enabled by default. It doesn't provide a query key for a collision however. This check is also delayed to the next incremental session. We also have the `verify_query_key_hashes` which is also enabled if `-Z incremental-verify-ich` is passed or `debug_assertions` is on. This checks for dep node conflicts in each query cache and provides 2 conflicting keys if present. I think these remaining checks are sufficient and so we can remove `nodes_in_current_session`.

Mark-Simulacrum · 2026-04-23T01:29:43Z

@rust-timer build 1a7e42e

rust-timer · 2026-04-23T02:10:12Z

Finished benchmarking commit (1a7e42e): comparison URL.

Overall result: ❌✅ regressions and improvements - please read:

Benchmarking means the PR may be perf-sensitive. It's automatically marked not fit for rolling up. Overriding is possible but disadvised: it risks changing compiler perf.

Next, please: If you can, justify the regressions found in this try perf run in writing along with @rustbot label: +perf-regression-triaged. If not, fix the regressions and do another perf run. Neutral or positive results will clear the label automatically.

@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)	0.7%	[0.0%, 2.0%]	3
Improvements ✅ (primary)	-0.8%	[-3.6%, -0.2%]	95
Improvements ✅ (secondary)	-1.3%	[-5.3%, -0.0%]	73
All ❌✅ (primary)	-0.8%	[-3.6%, -0.2%]	95

Max RSS (memory usage)

Results (primary -6.1%, secondary -5.5%)

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)	5.3%	[1.4%, 8.2%]	6
Improvements ✅ (primary)	-6.1%	[-11.4%, -1.5%]	156
Improvements ✅ (secondary)	-6.6%	[-19.8%, -1.3%]	56
All ❌✅ (primary)	-6.1%	[-11.4%, -1.5%]	156

Cycles

Results (primary -4.6%, secondary -7.1%)

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)	3.4%	[3.4%, 3.4%]	1
Improvements ✅ (primary)	-4.6%	[-13.5%, -2.0%]	70
Improvements ✅ (secondary)	-7.3%	[-21.7%, -2.4%]	52
All ❌✅ (primary)	-4.6%	[-13.5%, -2.0%]	70

Binary size

This perf run didn't have relevant results for this metric.

Bootstrap: 492.288s -> 492.321s (0.01%)
Artifact size: 394.44 MiB -> 394.35 MiB (-0.02%)

…uwer Rollup of 10 pull requests Successful merges: - rust-lang/rust#154794 (Add on_unmatch_args) - rust-lang/rust#155133 (Document precision considerations of `Duration`-float methods) - rust-lang/rust#154283 (Remove `nodes_in_current_session` field and related assertions) - rust-lang/rust#155374 (rustdoc: fix a few spots where emit isn't respected) - rust-lang/rust#155587 (Immediately feed visibility on DefId creation) - rust-lang/rust#155622 (c-variadic: `va_arg` fixes ) - rust-lang/rust#155629 (rustc_public: Add `constness` & `asyncness` in `FnDef`) - rust-lang/rust#155632 (Some metadata cleanups) - rust-lang/rust#155639 (BinOpAssign always returns unit) - rust-lang/rust#155647 (rustc-dev-guide subtree update)

rustbot assigned jdonszelmann Mar 24, 2026

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. labels Mar 24, 2026

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Zoxc force-pushed the rem-nodes_in_current_session branch from 922660c to 267d6cf Compare March 24, 2026 00:49

rustbot assigned nnethercote and unassigned jdonszelmann Apr 2, 2026

nnethercote reviewed Apr 5, 2026

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nnethercote added S-waiting-on-author Status: This is awaiting some action (such as code changes or more information) from the author. and removed S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. labels Apr 5, 2026

Zoxc force-pushed the rem-nodes_in_current_session branch from 267d6cf to 14b2173 Compare April 12, 2026 16:04

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nnethercote reviewed Apr 13, 2026

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Zoxc force-pushed the rem-nodes_in_current_session branch from 14b2173 to 736242c Compare April 21, 2026 02:22

Remove nodes_in_current_session field and related assertions

0add85c

Zoxc force-pushed the rem-nodes_in_current_session branch from 736242c to 0add85c Compare April 21, 2026 03:05

nnethercote approved these changes Apr 22, 2026

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rust-bors Bot 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-author Status: This is awaiting some action (such as code changes or more information) from the author. labels Apr 22, 2026

JonathanBrouwer mentioned this pull request Apr 22, 2026

Rollup of 10 pull requests #155655

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rust-bors Bot merged commit 8bade03 into rust-lang:main Apr 22, 2026
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rustbot added this to the 1.97.0 milestone Apr 22, 2026

Zoxc deleted the rem-nodes_in_current_session branch April 22, 2026 23:52

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rustbot added the perf-regression Performance regression. label Apr 23, 2026

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rust-timer commented Apr 23, 2026

Overall result: ❌✅ regressions and improvements - please read:

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