Make lowering incremental, take 3/N by cjgillot · Pull Request #142830 · rust-lang/rust

cjgillot · 2025-06-21T15:26:00Z

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Rebase of #88186 that was rebased by #127262

No real change in design, so I'm not expecting a perf miracle.

r? @ghost

cjgillot · 2025-06-21T16:12:09Z

@bors try @rust-timer queue

bors · 2025-06-21T16:13:19Z

⌛ Trying commit 0e2f90b with merge a6b131d...

Make lowering incremental, take 3/N Rebase of #88186 that was rebased by #127262 No real change in design, so I'm not expecting a perf miracle. r? `@ghost`

bors · 2025-06-21T18:43:11Z

☀️ Try build successful - checks-actions
Build commit: a6b131d (a6b131d42573c085b032a153779366b448148b9d)

rust-timer · 2025-06-21T20:41:55Z

Finished benchmarking commit (a6b131d): comparison URL.

Overall result: ❌✅ regressions and improvements - please read the text below

Benchmarking this pull request means it may be perf-sensitive – we'll automatically label it not fit for rolling up. You can override this, but we strongly advise not to, due to possible changes in compiler perf.

Next Steps: If you can justify the regressions found in this try perf run, please do so in sufficient writing along with @rustbot label: +perf-regression-triaged. If not, please fix the regressions and do another perf run. If its results are neutral or positive, the label will be automatically removed.

@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)	0.8%	[0.2%, 1.8%]	157
Regressions ❌ (secondary)	1.1%	[0.2%, 4.3%]	69
Improvements ✅ (primary)	-0.4%	[-0.5%, -0.3%]	5
Improvements ✅ (secondary)	-0.3%	[-0.5%, -0.2%]	7
All ❌✅ (primary)	0.7%	[-0.5%, 1.8%]	162

Max RSS (memory usage)

Results (primary 10.5%, secondary 10.1%)

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

	mean	range	count
Regressions ❌ (primary)	10.5%	[3.1%, 28.6%]	249
Regressions ❌ (secondary)	10.1%	[2.2%, 31.4%]	142
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	10.5%	[3.1%, 28.6%]	249

Cycles

Results (primary 2.5%, secondary 4.1%)

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

	mean	range	count
Regressions ❌ (primary)	2.5%	[1.4%, 5.5%]	35
Regressions ❌ (secondary)	4.1%	[1.8%, 7.5%]	22
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	2.5%	[1.4%, 5.5%]	35

Binary size

Results (primary -0.1%, secondary -0.2%)

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)	-	-	0
Improvements ✅ (primary)	-0.1%	[-0.2%, -0.0%]	82
Improvements ✅ (secondary)	-0.2%	[-0.9%, -0.0%]	43
All ❌✅ (primary)	-0.1%	[-0.2%, -0.0%]	82

Bootstrap: 690.042s -> 689.298s (-0.11%)
Artifact size: 371.86 MiB -> 371.81 MiB (-0.01%)

cjgillot · 2025-06-22T16:12:05Z

@bors try @rust-timer queue

bors · 2025-06-22T16:13:39Z

⌛ Trying commit 8ab4e63 with merge 31325ff...

Make lowering incremental, take 3/N Rebase of #88186 that was rebased by #127262 No real change in design, so I'm not expecting a perf miracle. r? `@ghost`

bors · 2025-06-22T18:48:06Z

☀️ Try build successful - checks-actions
Build commit: 31325ff (31325ff312ad91d8a2dd156c832cacc0435f9ea1)

rust-timer · 2025-06-22T21:45:31Z

Finished benchmarking commit (31325ff): comparison URL.

Overall result: ❌✅ regressions and improvements - please read the text below

Benchmarking this pull request means it may be perf-sensitive – we'll automatically label it not fit for rolling up. You can override this, but we strongly advise not to, due to possible changes in compiler perf.

Next Steps: If you can justify the regressions found in this try perf run, please do so in sufficient writing along with @rustbot label: +perf-regression-triaged. If not, please fix the regressions and do another perf run. If its results are neutral or positive, the label will be automatically removed.

@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)	0.5%	[0.2%, 1.3%]	120
Regressions ❌ (secondary)	0.8%	[0.2%, 3.2%]	77
Improvements ✅ (primary)	-0.7%	[-1.3%, -0.2%]	12
Improvements ✅ (secondary)	-0.6%	[-1.3%, -0.2%]	37
All ❌✅ (primary)	0.4%	[-1.3%, 1.3%]	132

Max RSS (memory usage)

Results (primary 10.8%, secondary 10.4%)

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

	mean	range	count
Regressions ❌ (primary)	10.8%	[2.3%, 29.1%]	248
Regressions ❌ (secondary)	10.4%	[1.9%, 31.7%]	143
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	10.8%	[2.3%, 29.1%]	248

Cycles

Results (primary 2.1%, secondary 4.1%)

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

	mean	range	count
Regressions ❌ (primary)	2.1%	[1.2%, 3.8%]	20
Regressions ❌ (secondary)	4.1%	[1.7%, 6.6%]	16
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	2.1%	[1.2%, 3.8%]	20

Binary size

Results (primary -0.1%, secondary -0.2%)

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)	-	-	0
Improvements ✅ (primary)	-0.1%	[-0.2%, -0.0%]	83
Improvements ✅ (secondary)	-0.2%	[-0.9%, -0.0%]	43
All ❌✅ (primary)	-0.1%	[-0.2%, -0.0%]	83

Bootstrap: 689.082s -> 688.79s (-0.04%)
Artifact size: 371.89 MiB -> 371.87 MiB (-0.00%)

petrochenkov · 2026-06-15T15:39:34Z

r=me after addressing the remaining comments, responding to #142830 (comment), and cleaning up the git history.
@rustbot author

rustbot · 2026-06-15T15:39:39Z

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

Co-authored-by: Camille Gillot <gillot.camille@gmail.com>

rustbot · 2026-06-16T00:11:27Z

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 · 2026-06-16T11:15:54Z

@bors r=petrochenkov

rust-bors · 2026-06-16T11:15:56Z

📌 Commit 2a30bc0 has been approved by petrochenkov

It is now in the queue for this repository.

rust-bors · 2026-06-16T15:38:31Z

☀️ Test successful - CI
Approved by: petrochenkov
Duration: 3h 22m 34s
Pushing 89a9993 to main...

github-actions · 2026-06-16T15:41:58Z

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 b998449 (parent) -> 89a9993 (this PR)

Test differences

Show 116 test diffs

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

Test dashboard

Run

cargo run --manifest-path src/ci/citool/Cargo.toml -- \
    test-dashboard 89a99936d9e76a50e8df622e7242190841fd871b --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

i686-gnu-nopt-2: 1h 25m -> 2h 23m (+69.0%)
dist-powerpc64le-linux-gnu: 1h 6m -> 1h 34m (+42.3%)
x86_64-gnu-llvm-22-2: 1h 44m -> 1h 4m (-38.4%)
dist-x86_64-solaris: 1h 16m -> 1h 39m (+29.6%)
aarch64-apple: 3h 27m -> 2h 30m (-27.8%)
x86_64-mingw-1: 2h 17m -> 2h 54m (+27.6%)
test-various: 1h 46m -> 2h 13m (+25.6%)
dist-x86_64-illumos: 1h 25m -> 1h 47m (+25.6%)
dist-various-1: 1h 2m -> 1h 16m (+23.9%)
dist-x86_64-netbsd: 1h 32m -> 1h 10m (-23.6%)

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 · 2026-06-16T16:20:42Z

Finished benchmarking commit (89a9993): comparison URL.

Overall result: ❌ regressions - 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)	0.8%	[0.1%, 2.7%]	172
Regressions ❌ (secondary)	1.1%	[0.1%, 4.2%]	105
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-0.4%	[-0.4%, -0.4%]	1
All ❌✅ (primary)	0.8%	[0.1%, 2.7%]	172

Max RSS (memory usage)

Results (primary 3.3%, 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)	3.3%	[1.0%, 12.3%]	145
Regressions ❌ (secondary)	2.9%	[1.3%, 5.6%]	30
Improvements ✅ (primary)	-2.8%	[-2.8%, -2.8%]	1
Improvements ✅ (secondary)	-5.3%	[-11.5%, -1.1%]	11
All ❌✅ (primary)	3.3%	[-2.8%, 12.3%]	146

Cycles

Results (primary 2.4%, secondary 2.7%)

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

	mean	range	count
Regressions ❌ (primary)	2.9%	[2.1%, 3.7%]	10
Regressions ❌ (secondary)	4.7%	[2.7%, 8.1%]	23
Improvements ✅ (primary)	-2.6%	[-2.6%, -2.6%]	1
Improvements ✅ (secondary)	-3.8%	[-4.9%, -2.2%]	7
All ❌✅ (primary)	2.4%	[-2.6%, 3.7%]	11

Binary size

Results (primary 0.0%, secondary 0.0%)

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

	mean	range	count
Regressions ❌ (primary)	0.0%	[0.0%, 0.0%]	1
Regressions ❌ (secondary)	0.0%	[0.0%, 0.0%]	1
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	0.0%	[0.0%, 0.0%]	1

Bootstrap: 524.623s -> 522.035s (-0.49%)
Artifact size: 401.77 MiB -> 401.81 MiB (0.01%)

oli-obk · 2026-06-16T18:39:59Z

@rustbot label: +perf-regression-triaged

This is unavoidable without making this PR bitrot for a long time and much more complex. I have various ideas for improving perf here, which I am pursuing as part of rust-lang/rust-project-goals#620

rustbot added PG-exploit-mitigations Project group: Exploit mitigations T-compiler Relevant to the compiler team, which will review and decide on the PR/issue. T-rustdoc Relevant to the rustdoc team, which will review and decide on the PR/issue. labels Jun 21, 2025

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cjgillot force-pushed the lower-incr-2 branch from d715668 to 0e2f90b Compare June 21, 2025 16:11

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bors added a commit that referenced this pull request Jun 21, 2025

Auto merge of #142830 - cjgillot:lower-incr-2, r=<try>

a6b131d

Make lowering incremental, take 3/N Rebase of #88186 that was rebased by #127262 No real change in design, so I'm not expecting a perf miracle. r? `@ghost`

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rustbot added perf-regression Performance regression. and removed S-waiting-on-perf Status: Waiting on a perf run to be completed. labels Jun 21, 2025

cjgillot force-pushed the lower-incr-2 branch from 0e2f90b to 8ab4e63 Compare June 22, 2025 16:11

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rustbot added the S-waiting-on-perf Status: Waiting on a perf run to be completed. label Jun 22, 2025

bors added a commit that referenced this pull request Jun 22, 2025

Auto merge of #142830 - cjgillot:lower-incr-2, r=<try>

31325ff

Make lowering incremental, take 3/N Rebase of #88186 that was rebased by #127262 No real change in design, so I'm not expecting a perf miracle. r? `@ghost`

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bors mentioned this pull request Jun 22, 2025

Document subdirectories of UI tests with README files #141597

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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 Jun 15, 2026

oli-obk removed their assignment Jun 15, 2026

cjgillot added 8 commits June 15, 2026 23:24

Stop stealing ResolverAstLowering.

bfe40ed

Make lowering incremental.

334a95f

Co-authored-by: Camille Gillot <gillot.camille@gmail.com>

Precompute hash for OwnerInfo too.

0b8a18a

Split-up the AST to index it.

5464994

Steal ResolverAstLowering when indexing AST.

0e9f931

Document AstOwner.

8e92278

Document HIR queries.

24c18c4

std::mem is already imported.

2a30bc0

cjgillot force-pushed the lower-incr-2 branch from a470321 to 2a30bc0 Compare June 16, 2026 00:11

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 Jun 16, 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 Jun 16, 2026

rust-bors Bot merged commit 89a9993 into rust-lang:main Jun 16, 2026
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rust-bors Bot mentioned this pull request Jun 16, 2026

Computing crate_hash from metadata encoding instead of HIR (implements #94878) #154724

Open

aerooneqq mentioned this pull request Jun 17, 2026

delegation: add simple test for incremental compilation #158019

Merged

oli-obk mentioned this pull request Jul 8, 2026

Architectural groundwork for expansion-time evaluation rust-lang/rust-project-goals#620

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rust-timer commented Jun 21, 2025

Overall result: ❌✅ regressions and improvements - please read the text below

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rust-timer commented Jun 22, 2025

Overall result: ❌✅ regressions and improvements - please read the text below

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Test differences

Job duration changes

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rust-timer commented Jun 16, 2026

Overall result: ❌ regressions - please read:

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cjgillot commented Jun 21, 2025 •

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