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Resolver: split module resolutions into local and external resolutions - #160099

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LorrensP-2158466:split-module-resolutions
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Resolver: split module resolutions into local and external resolutions#160099
LorrensP-2158466 wants to merge 1 commit into
rust-lang:mainfrom
LorrensP-2158466:split-module-resolutions

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@LorrensP-2158466 LorrensP-2158466 commented Jul 28, 2026 •
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Part of #158845.

This pr splits the resolution table for local and external modules, with the external table being wrapped in a OnceLock, because only 1 thread may create that table in parallel resolution.

r? @petrochenkov

@rustbot 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 Jul 28, 2026
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petrochenkov commented Jul 28, 2026

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@bors try @rust-timer queue

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@rustbot rustbot added the S-waiting-on-perf Status: Waiting on a perf run to be completed. label Jul 28, 2026
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rust-bors Bot pushed a commit that referenced this pull request Jul 28, 2026
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Auto merge of #160099 - LorrensP-2158466:split-module-resolutions, r=…
5fd6574 
…<try>

Resolver: split module resolutions into local and external resolutions
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☀️ Try build successful (CI)
Build commit: 5fd6574 (5fd657436197e7acfa920d848f00e619d7da2390)
Base parent: e19d321 (e19d321c06479c6fd77533582b0d5a86651f1be3)

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Finished benchmarking commit (5fd6574): comparison URL.

Overall result: ❌ regressions - no action needed

Benchmarking means the PR may be perf-sensitive. Consider adding rollup=never if this change is not fit for rolling up.

@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)		 0.3% [0.2%, 0.4%] 8
Improvements ✅
(primary)		 - - 0
Improvements ✅
(secondary)		 - - 0
All ❌✅ (primary) - - 0

Max RSS (memory usage)

Results (secondary -0.7%)

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% [5.3%, 5.3%] 1
Improvements ✅
(primary)		 - - 0
Improvements ✅
(secondary)		 -3.7% [-5.4%, -2.0%] 2
All ❌✅ (primary) - - 0

Cycles

Results (primary -1.4%, secondary -2.1%)

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)		 3.5% [2.7%, 4.2%] 2
Improvements ✅
(primary)		 -1.4% [-1.4%, -1.4%] 1
Improvements ✅
(secondary)		 -4.0% [-6.1%, -2.3%] 6
All ❌✅ (primary) -1.4% [-1.4%, -1.4%] 1

Binary size

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

Bootstrap: 490.165s -> 490.132s (-0.01%)
Artifact size: 388.34 MiB -> 390.34 MiB (0.52%)

@rustbot rustbot removed the S-waiting-on-perf Status: Waiting on a perf run to be completed. label Jul 29, 2026
@LorrensP-2158466

LorrensP-2158466 commented Jul 29, 2026

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Increased cycle count is expected due to OnceLock doing a synchronized load of its state, but its less than expected. I don't think it would benefit from having a dynamic synchronized version like Lock.

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petrochenkov commented Jul 29, 2026

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include-blob is irrelevant noise in this case, that benchmark doesn't even have modules, and replacing Once with OnceLock shouldn't be a regression.

petrochenkov
petrochenkov reviewed Jul 29, 2026
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Comment thread compiler/rustc_resolve/src/lib.rs Outdated
Comment thread compiler/rustc_resolve/src/lib.rs Outdated
}

type Resolutions<'ra> = CmRefCell<FxIndexMap<BindingKey, NameResolutionRef<'ra>>>;
type ResolutionTable<'ra> = CmRefCell<FxIndexMap<BindingKey, NameResolutionRef<'ra>>>;

@petrochenkov petrochenkov Jul 29, 2026 •
edited by rustbot
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The extern version of the table doesn't need CmRefCell, because it's never mutated.
But you'll have to either dismantle fn resolutions, or introduce something like CmRef to avoid it.

View changes since the review

@LorrensP-2158466 LorrensP-2158466 Jul 29, 2026

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I'll try it next.

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petrochenkov commented Jul 29, 2026

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r=me after addressing #160099 (comment).
@rustbot author

@rustbot rustbot 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 Jul 29, 2026
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Reminder, once the PR becomes ready for a review, use @rustbot ready.

@LorrensP-2158466
split module resolutions into local and external types, with external…
580253e 
… having a `OnceLock` around it for parallel import resolution
@LorrensP-2158466
LorrensP-2158466 force-pushed the split-module-resolutions branch from 7a2d086 to 580253e Compare July 29, 2026 12:41
@LorrensP-2158466

LorrensP-2158466 commented Jul 29, 2026

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r=me after addressing

Can't do that :D, @rustbot ready.

@rustbot 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 Jul 29, 2026
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petrochenkov commented Jul 29, 2026

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@bors r+ rollup

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rust-bors Bot commented Jul 29, 2026

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📌 Commit 580253e has been approved by petrochenkov

It is now in the queue for this repository.

@rust-bors 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-review Status: Awaiting review from the assignee but also interested parties. labels Jul 29, 2026
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