Closures inherit #[optimize] from the enclosing function by default. by veluca93 · Pull Request #158901 · rust-lang/rust

veluca93 · 2026-07-07T08:39:44Z

Tracking issue: #54882
Stabilization PR: #157273

rustbot · 2026-07-07T08:39:50Z

rustbot has assigned @fee1-dead.
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fee1-dead · 2026-07-09T17:21:13Z

Waiting on t-lang per #157273 (comment)

tmandry · 2026-07-16T01:42:48Z

The lang team discussed this change today and was in favor: #157562 (comment)

veluca93 · 2026-07-18T09:58:26Z

I don't believe this is blocked on lang anymore, but I don't think I can remove the tag myself.

fee1-dead

r? scottmcm
could you check if the codegen-llvm CHECK annotations here are idiomatic or is there a better way?

View changes since this review

rustbot · 2026-07-22T03:51:18Z

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

veluca93 · 2026-07-22T05:50:27Z

@rustbot ready

wesleywiser · 2026-07-23T17:56:58Z

FileCheck tests look fine to me but maybe @scottmcm knows better 🙂

@bors rollup=never

Could have perf implications from changing effective optimization values for closures.

scottmcm

cg_ssa bit of this looks plausible to me; just a couple thoughts about the codegen test.

(Feel free to push back if they won't work or get ugly for some reason.)

View changes since this review

scottmcm · 2026-07-24T15:57:49Z

+#![crate_type = "lib"]
+
+// CHECK-DAG: define{{.*}}void {{.*}}test_none{{.*}}call_once{{.*}}#[[ATTR_NONE:[0-9]+]]
+// CHECK-DAG: define{{.*}}void {{.*}}test_none{{.*}}B{{[0-9]+}}_() {{.*}}#[[ATTR_NONE]]


Possibly a silly question: what's that B from?

(I get worried about anything too specific in name checks because we've been bitten before by people doing things like %[[FOO]].0 and depending on the exact internal LLVM naming of SRoA results and such. This is probably not that bad, but I'm confused what it is, so...)

I personally don't know, but $LLM seems to think it comes from "Rust's v0 symbol mangling specification (specifically compression back-references for path components, e.g. B3_)". However with no-prepopulate-passes this doesn't seem needed anymore, so ... :-)

(I don't really understand FileCheck)

scottmcm · 2026-07-25T23:56:59Z

@bors r=wesleywiser,scottmcm

rust-bors · 2026-07-25T23:57:02Z

📌 Commit cca3d28 has been approved by wesleywiser,scottmcm

It is now in the queue for this repository.

🌲 The tree is currently closed for pull requests below priority 100. This pull request will be tested once the tree is reopened.

Reason for tree closure: spurious failures

it's my review

JonathanBrouwer · 2026-07-26T17:03:26Z

@bors p=101
Scheduling

rust-bors · 2026-07-26T20:11:01Z

☀️ Test successful - CI
Approved by: wesleywiser,scottmcm
Duration: 3h 7m 14s
Pushing 5e2e873 to main...

github-actions · 2026-07-26T20:14:25Z

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 9451e06 (parent) -> 5e2e873 (this PR)

Test differences

Show 5 test diffs

Stage 1

[codegen] tests/codegen-llvm/optimize-closures-inheritance.rs: [missing] -> pass (J1)

Stage 2

[codegen] tests/codegen-llvm/optimize-closures-inheritance.rs: [missing] -> pass (J0)

Additionally, 3 doctest diffs were found. These are ignored, as they are noisy.

Job group index

Test dashboard

Run

cargo run --manifest-path src/ci/citool/Cargo.toml -- \
    test-dashboard 5e2e8734b6a10a88879b8732fec64dd524894793 --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-rust-for-linux: 31m 38s -> 47m 25s (+49.9%)
dist-i686-msvc: 1h 27m -> 2h 4m (+43.4%)
test-various: 1h 28m -> 2h 4m (+40.1%)
dist-powerpc64le-linux-gnu: 1h 15m -> 1h 40m (+33.0%)
dist-x86_64-musl: 1h 45m -> 2h 16m (+29.8%)
arm-android: 1h 19m -> 1h 42m (+29.6%)
dist-powerpc64le-linux-musl: 1h 19m -> 1h 37m (+23.5%)
x86_64-gnu-gcc-core-tests: 8m 10s -> 6m 16s (-23.4%)
x86_64-gnu-distcheck: 2h 13m -> 1h 42m (-23.0%)
dist-x86_64-freebsd: 1h 11m -> 1h 27m (+22.6%)

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 · 2026-07-26T21:26:52Z

Finished benchmarking commit (5e2e873): comparison URL.

Overall result: no relevant changes - no action needed

@rustbot label: -perf-regression

Instruction count

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

Max RSS (memory usage)

Results (primary 2.1%, secondary 0.4%)

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

	mean	range	count
Regressions ❌ (primary)	2.1%	[2.1%, 2.1%]	1
Regressions ❌ (secondary)	1.7%	[1.2%, 2.2%]	2
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-2.2%	[-2.2%, -2.2%]	1
All ❌✅ (primary)	2.1%	[2.1%, 2.1%]	1

Cycles

Results (secondary -3.4%)

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)	-3.4%	[-3.7%, -3.0%]	2
All ❌✅ (primary)	-	-	0

Binary size

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

Bootstrap: 489.176s -> 487.552s (-0.33%)
Artifact size: 387.73 MiB -> 387.70 MiB (-0.01%)

rustbot assigned fee1-dead Jul 7, 2026

rustbot added A-attributes Area: Attributes (`#[…]`, `#![…]`) 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 7, 2026

veluca93 mentioned this pull request Jul 7, 2026

Stabilize optimize attribute #157273

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fee1-dead added S-waiting-on-t-lang Status: Awaiting decision from T-lang and removed S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. labels Jul 9, 2026

fee1-dead added I-lang-nominated Nominated for discussion during a lang team meeting. and removed I-lang-nominated Nominated for discussion during a lang team meeting. labels Jul 9, 2026

mejrs added S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. and removed S-waiting-on-t-lang Status: Awaiting decision from T-lang labels Jul 21, 2026

fee1-dead requested changes Jul 22, 2026

View reviewed changes

Comment thread tests/codegen-llvm/optimize-closures-inheritance.rs

rustbot assigned scottmcm and unassigned fee1-dead Jul 22, 2026

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 22, 2026

veluca93 force-pushed the optimize-attr-closure-inherit branch from 3c5ebd5 to f24fa6f Compare July 22, 2026 05:49

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 22, 2026

wesleywiser approved these changes Jul 23, 2026

View reviewed changes

scottmcm previously requested changes Jul 24, 2026

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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 24, 2026

Closures inherit #[optimize] from the enclosing function by default.

cca3d28

veluca93 force-pushed the optimize-attr-closure-inherit branch from f24fa6f to cca3d28 Compare July 25, 2026 18:42

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 Jul 25, 2026

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rust-bors Bot added merged-by-bors This PR was explicitly merged by bors. and removed S-waiting-on-bors Status: Waiting on bors to run and complete tests. Bors will change the label on completion. labels Jul 26, 2026

rust-bors Bot merged commit 5e2e873 into rust-lang:main Jul 26, 2026
14 checks passed

rustbot added this to the 1.99.0 milestone Jul 26, 2026

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veluca93 commented Jul 7, 2026

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Test differences

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Job duration changes

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rust-timer commented Jul 26, 2026

Overall result: no relevant changes - no action needed

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