Move lang item collection to the resolver by oli-obk · Pull Request #163525 · rust-lang/rust

oli-obk · 2026-09-30T08:13:15Z

The separate query had to walk the entire ast again, also tracking owners and converting NodeIds to DefIds. I think it's nicer to just do it as part of the resolver.

Alternatively we could limit the lang item collection to the local ones and keep the query. Instead of walking the current crate again we'd just take the list from the resolver query just like we take the list from upstream crates.

oli-obk · 2026-09-30T08:13:29Z

@bors try @rust-timer queue

Move lang item collection to the resolver

rust-bors · 2026-09-30T09:12:00Z

☀️ Try build successful (CI)
Build commit: ee7b1cf (ee7b1cf2bee32b699e66c83d9f1a5707b555c962)
Base parent: c1bf6e1 (c1bf6e13fa5ff2c753a49fd5ef37371c6fed729f)

rust-timer · 2026-09-30T12:42:57Z

Finished benchmarking commit (ee7b1cf): comparison URL.

Overall result: ✅ improvements - no action needed

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.

@bors rollup=never rustc-perf
@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
Improvements ✅ (primary)	-0.2%	[-0.6%, -0.1%]	67
Improvements ✅ (secondary)	-0.3%	[-0.8%, -0.1%]	30
All ❌✅ (primary)	-0.2%	[-0.6%, -0.1%]	67

Max RSS (memory usage)

Results (secondary 1.3%)

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)	2.7%	[1.4%, 5.9%]	5
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-5.7%	[-5.7%, -5.7%]	1
All ❌✅ (primary)	-	-	0

Cycles

Results (primary 1.5%, secondary -0.3%)

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

	mean	range	count
Regressions ❌ (primary)	1.5%	[1.5%, 1.5%]	1
Regressions ❌ (secondary)	4.0%	[4.0%, 4.0%]	1
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-2.4%	[-2.8%, -2.1%]	2
All ❌✅ (primary)	1.5%	[1.5%, 1.5%]	1

Binary size

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

Bootstrap: 489.184s -> 489.805s (0.13%)
Artifact size: 406.44 MiB -> 406.38 MiB (-0.01%)

oli-obk · 2026-09-30T14:12:57Z

r? @petrochenkov

rustbot · 2026-09-30T14:13:04Z

These commits modify the Cargo.lock file. Unintentional changes to Cargo.lock can be introduced when switching branches and rebasing PRs.

If this was unintentional then you should revert the changes before this PR is merged.
Otherwise, you can ignore this comment.

petrochenkov · 2026-10-13T14:35:10Z

Alternatively we could limit the lang item collection to the local ones and keep the query. Instead of walking the current crate again we'd just take the list from the resolver query just like we take the list from upstream crates.

It probably doesn't matter much where exactly the set of extern crates is walked, in rustc_resolve or later in rustc_passes (from a query)?
The full list of lang items is going to be queried anyway, unless something rare happens, like an early enough fatal error.

oli-obk · 2026-10-23T16:32:38Z

@rustbot ready

addressed the review comments

petrochenkov · 2026-10-26T16:03:57Z

@bors r+

JonathanBrouwer · 2026-10-27T09:59:27Z

@bors rollup=iffy
Making a rollup of perf-sensitive PRs

…rochenkov Move lang item collection to the resolver The separate query had to walk the entire ast again, also tracking owners and converting NodeIds to DefIds. I think it's nicer to just do it as part of the resolver. Alternatively we could limit the lang item collection to the local ones and keep the query. Instead of walking the current crate again we'd just take the list from the resolver query just like we take the list from upstream crates.

…uwer Rollup of 3 perf-sensitive pull requests Successful merges: - #163525 (Move lang item collection to the resolver) - #164234 (New solver opts for `diesel` (part 2)) - #164726 (perf: emit field names as a concatenated string in derive(Debug) for structs)

…rochenkov Move lang item collection to the resolver The separate query had to walk the entire ast again, also tracking owners and converting NodeIds to DefIds. I think it's nicer to just do it as part of the resolver. Alternatively we could limit the lang item collection to the local ones and keep the query. Instead of walking the current crate again we'd just take the list from the resolver query just like we take the list from upstream crates.

…uwer Rollup of 5 perf-sensitive pull requests Successful merges: - #165032 (stdarch subtree update) - #163525 (Move lang item collection to the resolver) - #164234 (New solver opts for `diesel` (part 2)) - #164726 (perf: emit field names as a concatenated string in derive(Debug) for structs) - #164953 (Avoid stdlib's `impl Hash for Discriminant` for stable hashing)

…rochenkov Move lang item collection to the resolver The separate query had to walk the entire ast again, also tracking owners and converting NodeIds to DefIds. I think it's nicer to just do it as part of the resolver. Alternatively we could limit the lang item collection to the local ones and keep the query. Instead of walking the current crate again we'd just take the list from the resolver query just like we take the list from upstream crates.

…uwer Rollup of 5 perf-sensitive pull requests Successful merges: - #163525 (Move lang item collection to the resolver) - #164234 (New solver opts for `diesel` (part 2)) - #164726 (perf: emit field names as a concatenated string in derive(Debug) for structs) - #164953 (Avoid stdlib's `impl Hash for Discriminant` for stable hashing) - #164969 (perf: avoid allocating HashSet in is_distinct check on small SwitchInts)

…rochenkov Move lang item collection to the resolver The separate query had to walk the entire ast again, also tracking owners and converting NodeIds to DefIds. I think it's nicer to just do it as part of the resolver. Alternatively we could limit the lang item collection to the local ones and keep the query. Instead of walking the current crate again we'd just take the list from the resolver query just like we take the list from upstream crates.

rustbot · 2026-10-29T11:16:52Z

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.

oli-obk · 2026-10-29T11:16:57Z

@bors r=petrochenkov

rust-bors · 2026-10-29T11:17:01Z

📌 Commit 5156c51 has been tentatively approved by petrochenkov

It will be put into the queue for this repository once PR CI succeeds.

JonathanBrouwer · 2026-10-29T13:56:22Z

@bors rollup=never
This missed the perf-sensitive rollup (tho there will be another one later)

JonathanBrouwer · 2026-10-30T18:24:02Z

@bors rollup=iffy
Making a rollup of perf sensitive prs

…rochenkov Move lang item collection to the resolver The separate query had to walk the entire ast again, also tracking owners and converting NodeIds to DefIds. I think it's nicer to just do it as part of the resolver. Alternatively we could limit the lang item collection to the local ones and keep the query. Instead of walking the current crate again we'd just take the list from the resolver query just like we take the list from upstream crates.

…uwer Rollup of 7 perf-sensitive pull requests Successful merges: - #163339 (MIR move elimination [5/6]: Storage reconstruction) - #163525 (Move lang item collection to the resolver) - #163928 (do not prefer trivially true candidates with `-Znext-solver` ) - #164341 (Expand an early return case in `coerce_unsized`) - #164484 (Use adaptive sparse encoding for metadata tables) - #164607 (destringlyfy lint infrastructure) - #165160 (New solver opts for diesel (part 3)) > [!WARNING] > This rollup conflicts with pending auto build #165178 and may need to be recreated if the pending build succeeds.

rustbot added S-waiting-on-author Status: This is awaiting some action (such as code changes or more information) from the author. T-compiler Relevant to the compiler team, which will review and decide on the PR/issue. labels Sep 30, 2026

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rust-bors Bot pushed a commit that referenced this pull request Sep 30, 2026

Auto merge of #163525 - oli-obk:resolver_lang_items, r=<try>

ee7b1cf

Move lang item collection to the resolver

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rustbot removed the S-waiting-on-perf Status: Waiting on a perf run to be completed. label Sep 30, 2026

rustbot assigned petrochenkov Sep 30, 2026

oli-obk marked this pull request as ready for review September 30, 2026 14:13

rustbot added S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. and removed S-waiting-on-author Status: This is awaiting some action (such as code changes or more information) from the author. labels Sep 30, 2026

petrochenkov reviewed Oct 13, 2026

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Comment thread compiler/rustc_resolve/src/late/weak_lang_items.rs Resolved

Comment thread compiler/rustc_resolve/src/late/lang_items.rs Resolved

Comment thread compiler/rustc_resolve/src/late/lang_items.rs Resolved

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oli-obk force-pushed the resolver_lang_items branch from 90ed939 to 18b002a Compare October 23, 2026 16:31

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oli-obk force-pushed the resolver_lang_items branch from 18b002a to 5221654 Compare October 26, 2026 10:25

rust-bors Bot removed the S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. label Oct 27, 2026

JonathanBrouwer mentioned this pull request Oct 27, 2026

Rollup of 3 perf-sensitive pull requests #165031

Closed

JonathanBrouwer mentioned this pull request Oct 27, 2026

Rollup of 5 perf-sensitive pull requests #165042

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JonathanBrouwer mentioned this pull request Oct 27, 2026

Rollup of 5 perf-sensitive pull requests #165057

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JonathanBrouwer mentioned this pull request Oct 28, 2026

Rollup of 7 perf-sensitive pull requests #165084

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Move lang item collection to the resolver

5156c51

oli-obk force-pushed the resolver_lang_items branch from 5221654 to 5156c51 Compare October 29, 2026 11:16

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 Oct 29, 2026

JonathanBrouwer mentioned this pull request Oct 30, 2026

Rollup of 7 perf-sensitive pull requests #165205

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rust-timer commented Sep 30, 2026

Overall result: ✅ improvements - no action needed

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