Rollup of 4 perf-sensitive pull requests by JonathanBrouwer · Pull Request #162859 · rust-lang/rust

JonathanBrouwer · 2026-09-16T18:09:54Z

Successful merges:

Cache block seeking results for initialized_at_terminator and _exit #162450 (Cache block seeking results for initialized_at_terminator and _exit)
[rustc_resolve] Correctly keep all reexports in ModChild::reexport_chain #162543 ([rustc_resolve] Correctly keep all reexports in ModChild::reexport_chain)
perf: Keep the first macro syntax-context mapping inline #162712 (perf: Keep the first macro syntax-context mapping inline)
AST lowering cleanups #162747 (Lowering cleanups)

Because it is derived from `PerOwnerLoweringState::owner`.

They are constants but they don't look like it because they are stored in fields. This commit makes them statics. `allow_gen_future` becomes a method because its value depends on `async_fn_track_caller`.

Cache block seeking results for initialized_at_terminator and _exit Caching the block values post-seek results in significant performance wins (especially on pathological benchmarks). These wins extend to NLL, too. Possibly, this caching could be done further up the stack (more generically), but figured this is a "safer" approach - rather than dealing with other potential fallout. r? lqd

@petrochenkov

…ient-crates, r=petrochenkov [rustc_resolve] Correctly keep all reexports in `ModChild::reexport_chain` Fixes rust-lang#81893. First commit comes from rust-lang#161872 and it's the base I used for the fix in the second commit (which also reverts basically everything from the first commit, not sure if I should keep it...). In short, `NameResolution` only seems to have access to local reexports and to the final reexported item. So instead, we keep the information in `DeclKind` (which cannot implement `Drop` because it's part of `DeclData` which is stored in `ResolverArenas::dropless` so I kept a slice instead of a `SmallVec`. Guess how I found out? Lots of `panic`s :') ) and we use this information in `reexport_chain`. r? @petrochenkov

…ker-first-context, r=petrochenkov perf: Keep the first macro syntax-context mapping inline

@spastorino

…pastorino Lowering cleanups Details in the individual commits. r? @spastorino

JonathanBrouwer · 2026-09-16T18:10:03Z

@bors r+ p=5

Trying commonly failed jobs
@bors try jobs=dist-various-1,test-various,test-x86_64-gnu-aux,test-x86_64-gnu-llvm-21-3,test-x86_64-msvc-1,test-aarch64-apple-1,test-aarch64-apple-2,test-x86_64-mingw-1,test-i686-msvc,test-armhf-gnu

rust-bors · 2026-09-16T18:10:06Z

📌 Commit 2792a2e has been approved by JonathanBrouwer

It is now in the queue for this repository.

Rollup of 4 pull requests try-job: dist-various-1 try-job: test-various try-job: test-x86_64-gnu-aux try-job: test-x86_64-gnu-llvm-21-3 try-job: test-x86_64-msvc-1 try-job: test-aarch64-apple-1 try-job: test-aarch64-apple-2 try-job: test-x86_64-mingw-1 try-job: test-i686-msvc try-job: test-armhf-gnu

…uwer Rollup of 4 perf-sensitive pull requests Successful merges: - #162450 (Cache block seeking results for initialized_at_terminator and _exit) - #162543 ([rustc_resolve] Correctly keep all reexports in `ModChild::reexport_chain`) - #162712 (perf: Keep the first macro syntax-context mapping inline) - #162747 (Lowering cleanups)

rust-log-analyzer · 2026-09-16T21:17:52Z

The job test-armhf-gnu failed! Check out the build log: (web) (plain enhanced) (plain)

Click to see the possible cause of the failure (guessed by this bot)

rust-bors · 2026-09-16T21:19:15Z

💔 Test for bb1f487 failed: CI. Failed job:

auto - test-armhf-gnu (web logs, enhanced plaintext logs)

rust-bors · 2026-09-16T21:21:43Z

☀️ Try build successful (CI)
Build commit: 31adc06 (31adc06b1607eebdc770b9b14b462e6efe47f5c5)
Base parent: 92801ed (92801ede88f6c10e34df6976a4cfde40142585f2)

jhpratt · 2026-09-16T21:26:46Z

thread 'main' (201955) panicked at src/tools/remote-test-client/src/main.rs:374:5:
io::copy(&mut file, dst) failed with Connection reset by peer (os error 104)

@bors retry

@bors try jobs=test-armhf-gnu

…uwer Rollup of 4 perf-sensitive pull requests Successful merges: - #162450 (Cache block seeking results for initialized_at_terminator and _exit) - #162543 ([rustc_resolve] Correctly keep all reexports in `ModChild::reexport_chain`) - #162712 (perf: Keep the first macro syntax-context mapping inline) - #162747 (Lowering cleanups)

Zalathar · 2026-09-17T00:38:46Z

Let's also do a try job in parallel to get a second opinion.

@bors try jobs=test-aarch64-msvc-1

Rollup of 4 perf-sensitive pull requests try-job: test-aarch64-msvc-1

rust-bors · 2026-09-17T01:42:34Z

💔 Test for eec2d1e failed: CI. Failed job:

auto - dist-powerpc-linux (web logs, enhanced plaintext logs)

Zalathar · 2026-09-17T02:12:02Z

Couldn’t get logs, so the failure is probably bogus.

@bors retry

rust-bors · 2026-09-17T02:57:11Z

☀️ Try build successful (CI)
Build commit: 06e9b2d (06e9b2d604801311d3420b46b1ae056e9d9aae63)
Base parent: 923c95c (923c95cdf5ba65cea505aa2ea829f578e1506ed8)

rust-bors · 2026-09-17T06:06:37Z

☀️ Test successful - CI
Approved by: JonathanBrouwer
Duration: 3h 7m 1s
Pushing c999cef to main...

github-actions · 2026-09-17T06:10:07Z

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 923c95c (parent) -> c999cef (this PR)

Test differences

Show 7 test diffs

Stage 1

[rustdoc-html] tests/rustdoc-html/reexport/transient-reexports.rs: [missing] -> pass (J0)

Stage 2

[rustdoc-html] tests/rustdoc-html/reexport/transient-reexports.rs: [missing] -> pass (J1)

Additionally, 5 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 c999cef531ea9059e189e82fe0e82c5daf249bc9 --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

test-i686-msvc: 1h 41m -> 2h 37m (+54.4%)
test-various: 1h 28m -> 2h 12m (+50.5%)
test-x86_64-msvc-ext3: 1h 23m -> 2h 2m (+45.6%)
test-pr-check-2: 27m 34s -> 38m 28s (+39.5%)
test-x86_64-gnu-llvm-21-3: 1h 52m -> 1h 10m (-37.2%)
dist-ohos-armv7: 58m 15s -> 1h 16m (+32.0%)
dist-riscv64-linux-gnu: 1h 36m -> 1h 7m (-29.9%)
test-x86_64-gnu: 2h 35m -> 1h 49m (-29.3%)
dist-i586-gnu-i586-i686-musl: 20m 22s -> 26m 12s (+28.6%)
test-aarch64-apple-macos-26-2: 2h 37m -> 1h 53m (-28.2%)

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 · 2026-09-17T06:54:09Z

Finished benchmarking commit (c999cef): comparison URL.

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

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)	0.4%	[0.2%, 0.5%]	4
Regressions ❌ (secondary)	0.3%	[0.1%, 0.7%]	10
Improvements ✅ (primary)	-0.8%	[-5.9%, -0.1%]	123
Improvements ✅ (secondary)	-0.7%	[-5.5%, -0.1%]	71
All ❌✅ (primary)	-0.7%	[-5.9%, 0.5%]	127

Max RSS (memory usage)

Results (primary 2.3%, secondary 1.0%)

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

	mean	range	count
Regressions ❌ (primary)	2.3%	[2.3%, 2.3%]	1
Regressions ❌ (secondary)	3.5%	[1.1%, 5.9%]	6
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-4.1%	[-5.8%, -1.4%]	3
All ❌✅ (primary)	2.3%	[2.3%, 2.3%]	1

Cycles

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

Binary size

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

Bootstrap: 497.899s -> 500.132s (0.45%)
Artifact size: 406.75 MiB -> 406.81 MiB (0.01%)

rust-bors · 2026-09-17T07:11:06Z

📌 Perf builds for each rolled up PR:

PR#	Message	Perf Build Sha
#162450	Cache block seeking results for initialized_at_terminator a…	`89b00936ef55a626bd75ee72f99c8e9b00706742` (link)
#162543	[rustc_resolve] Correctly keep all reexports in `ModChild:…	`a289e4f2d3988ee608d21a0b0b11f4ab62c2c743` (link)
#162712	perf: Keep the first macro syntax-context mapping inline	`4395c62bef89d6fa2947faa559c6f0300e484c76` (link)
#162747	Lowering cleanups	`4da6ef728e49cf15904e12b742dbbc0b699821d9` (link)

parent commit: 923c95cdf5

In the case of a perf regression, run the following command with the SHAs of each PR you suspect might be the cause: @rust-timer triage $SHA1 $SHA2 $SHA3..., or run @rust-timer triage all to benchmark all rollup members.

JonathanBrouwer · 2026-09-17T07:14:56Z

@rust-timer triage all

rust-timer · 2026-09-17T07:15:00Z

Running triage with 31 benchmarks

Triage only executes the benchmarks on rollup members, that were changed significantly on the rollup.
For this rollup, these benchmarks are:

bitmaps-3.2.1
cargo-0.87.1
clap_derive-4.5.32
clap_derive-4.5.32-nll
coercions
deep-vector
derive
diesel-2.2.10
externs
helloworld
hyper-1.6.0
issue-88862
libc-0.2.172
many-assoc-items
match-stress
nalgebra-0.33.0
regex-automata-0.4.8
ripgrep-14.1.1
ripgrep-14.1.1-nll
serde-1.0.219
serde-1.0.219-new-solver
serde-1.0.219-nll
serde_derive-1.0.219
stm32f4-0.15.1
syn-2.0.101
syn-2.0.101-new-solver
tokio-1.53.1
tt-muncher
typenum-1.18.0
unicode-normalization-0.1.24
unused-warnings

#162450 `89b0093` Cache block seeking results for initialized_at_terminator and _exit

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)	-4.5%	[-5.8%, -3.6%]	12
Improvements ✅ (secondary)	-4.6%	[-5.3%, -4.0%]	3
All ❌✅ (primary)	-4.5%	[-5.8%, -3.6%]	12

Max RSS (memory usage)

Results (primary -3.1%, secondary 3.2%)

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)	3.2%	[2.3%, 4.0%]	2
Improvements ✅ (primary)	-3.1%	[-4.2%, -2.3%]	3
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	-3.1%	[-4.2%, -2.3%]	3

Cycles

Results (primary 0.5%)

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

	mean	range	count
Regressions ❌ (primary)	2.0%	[1.7%, 2.4%]	2
Regressions ❌ (secondary)	-	-	0
Improvements ✅ (primary)	-2.5%	[-2.5%, -2.5%]	1
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	0.5%	[-2.5%, 2.4%]	3

Binary size

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

#162543 `a289e4f` [rustc_resolve] Correctly keep all reexports in `ModChild::reexport_chain`

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)	0.4%	[0.2%, 0.8%]	11
Regressions ❌ (secondary)	0.4%	[0.3%, 0.7%]	5
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-0.8%	[-0.8%, -0.8%]	3
All ❌✅ (primary)	0.4%	[0.2%, 0.8%]	11

Max RSS (memory usage)

Results (primary -0.2%, secondary -1.6%)

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

	mean	range	count
Regressions ❌ (primary)	2.0%	[2.0%, 2.0%]	1
Regressions ❌ (secondary)	3.4%	[1.0%, 5.2%]	3
Improvements ✅ (primary)	-2.4%	[-2.4%, -2.4%]	1
Improvements ✅ (secondary)	-4.7%	[-5.5%, -4.1%]	5
All ❌✅ (primary)	-0.2%	[-2.4%, 2.0%]	2

Cycles

Results (primary 2.1%)

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)	-	-	0
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	2.1%	[2.1%, 2.1%]	1

Binary size

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

#162712 `4395c62` perf: Keep the first macro syntax-context mapping inline

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)	0.1%	[0.1%, 0.2%]	5
Improvements ✅ (primary)	-0.4%	[-0.9%, -0.2%]	38
Improvements ✅ (secondary)	-0.5%	[-0.9%, -0.2%]	17
All ❌✅ (primary)	-0.4%	[-0.9%, -0.2%]	38

Max RSS (memory usage)

Results (primary -1.2%, 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)	1.0%	[1.0%, 1.0%]	1
Regressions ❌ (secondary)	2.7%	[1.1%, 4.7%]	3
Improvements ✅ (primary)	-2.3%	[-2.3%, -2.3%]	2
Improvements ✅ (secondary)	-4.4%	[-4.6%, -4.1%]	4
All ❌✅ (primary)	-1.2%	[-2.3%, 1.0%]	3

Cycles

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

Binary size

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

#162747 `4da6ef7` Lowering cleanups

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)	0.2%	[0.1%, 0.2%]	3
Improvements ✅ (primary)	-0.3%	[-0.5%, -0.1%]	67
Improvements ✅ (secondary)	-0.6%	[-1.5%, -0.2%]	46
All ❌✅ (primary)	-0.3%	[-0.5%, -0.1%]	67

Max RSS (memory usage)

Results (primary -2.6%, secondary -2.0%)

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)	3.4%	[2.3%, 4.5%]	2
Improvements ✅ (primary)	-2.6%	[-2.6%, -2.6%]	1
Improvements ✅ (secondary)	-4.7%	[-5.1%, -4.1%]	4
All ❌✅ (primary)	-2.6%	[-2.6%, -2.6%]	1

Cycles

Results (secondary -2.6%)

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)	-2.6%	[-2.6%, -2.6%]	1
All ❌✅ (primary)	-	-	0

Binary size

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

lqd · 2026-09-17T08:36:14Z

#162543 (comment) should be the source of the regression

JonathanBrouwer · 2026-09-17T08:41:46Z

I'm aware, the goal of the triage run is to verify that the actual performance effect of the member PRs of this rollup matches the expected one from earlier perf runs

GuillaumeGomez and others added 10 commits September 15, 2026 23:31

resolve: Concatenate reexport chains from all crates

73b1560

Add regression test for reexport chain in transient crates

cb55fc7

Make PerOwnerLoweringState::owner_id a method

7b0c2f2

Because it is derived from `PerOwnerLoweringState::owner`.

Remove constant allow_* fields from LoweringContext

02cd125

They are constants but they don't look like it because they are stored in fields. This commit makes them statics. `allow_gen_future` becomes a method because its value depends on `async_fn_track_caller`.

Keep the first macro syntax-context mapping inline

677073f

Cache block seeking results for initialized_at_terminator and _exit

bbfef75

Rollup merge of rust-lang#162712 - xmakro:perf-review-20260907/22-mar…

867d696

…ker-first-context, r=petrochenkov perf: Keep the first macro syntax-context mapping inline

Rollup merge of rust-lang#162747 - nnethercote:lowering-cleanups, r=s…

2792a2e

…pastorino Lowering cleanups Details in the individual commits. r? @spastorino

rust-bors Bot added the rollup A PR which is a rollup label Sep 16, 2026

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 Sep 16, 2026

JonathanBrouwer changed the title ~~Rollup of 4 pull requests~~ Rollup of 4 perf-sensitive pull requests Sep 16, 2026

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rust-bors Bot mentioned this pull request Sep 17, 2026

Cache block seeking results for initialized_at_terminator and _exit #162450

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rust-bors Bot pushed a commit that referenced this pull request Sep 17, 2026

Auto merge of #162859 - JonathanBrouwer:rollup-0CDWDbo, r=<try>

06e9b2d

Rollup of 4 perf-sensitive pull requests try-job: test-aarch64-msvc-1

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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 Sep 17, 2026

rust-bors Bot merged commit c999cef into rust-lang:main Sep 17, 2026
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rustbot added this to the 1.100.0 milestone Sep 17, 2026

This was referenced Sep 17, 2026

Fix invalid suggestions and misleading notes for imports #162688

Open

Defer extra liveness calculation for Polonius Alpha #161938

Open

rustbot added the perf-regression Performance regression. label Sep 17, 2026

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Test differences

Stage 1

Stage 2

Job duration changes

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rust-timer commented Sep 17, 2026

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

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#162450 89b0093 Cache block seeking results for initialized_at_terminator and _exit

#162543 a289e4f [rustc_resolve] Correctly keep all reexports in ModChild::reexport_chain

#162712 4395c62 perf: Keep the first macro syntax-context mapping inline

#162747 4da6ef7 Lowering cleanups

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#162450 `89b0093` Cache block seeking results for initialized_at_terminator and _exit

#162543 `a289e4f` [rustc_resolve] Correctly keep all reexports in `ModChild::reexport_chain`

#162712 `4395c62` perf: Keep the first macro syntax-context mapping inline

#162747 `4da6ef7` Lowering cleanups