Parallelize AST -> HIR lowering by aerooneqq · Pull Request #163495 · rust-lang/rust

aerooneqq · 2026-09-29T16:11:54Z

Parallelize AST -> HIR lowering.

petrochenkov · 2026-09-29T16:13:24Z

Parallelize AST -> HIR lowering

rust-bors · 2026-09-29T17:15:29Z

☀️ Try build successful (CI)
Build commit: 79a91eb (79a91eb0736d9f47b5af3d4282e49ada6baa01ca)
Base parent: ea6bb45 (ea6bb45b74c24a026dab4187b1550e97b6985c8a)

rust-timer · 2026-09-29T18:00:35Z

Finished benchmarking commit (79a91eb): comparison URL.

Overall result: ❌ regressions - please read:

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.

Next, please: If you can, justify the regressions found in this try perf run in writing along with @rustbot label: +perf-regression-triaged. If not, fix the regressions and do another perf run. Neutral or positive results will clear the label automatically.

@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)	0.9%	[0.2%, 9.2%]	88
Regressions ❌ (secondary)	1.3%	[0.1%, 7.4%]	172
Improvements ✅ (primary)	-0.2%	[-0.2%, -0.2%]	1
Improvements ✅ (secondary)	-0.2%	[-0.2%, -0.2%]	1
All ❌✅ (primary)	0.9%	[-0.2%, 9.2%]	89

Max RSS (memory usage)

Results (primary 1.2%, 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)	1.8%	[1.1%, 2.8%]	4
Regressions ❌ (secondary)	3.3%	[1.7%, 7.2%]	10
Improvements ✅ (primary)	-0.9%	[-0.9%, -0.9%]	1
Improvements ✅ (secondary)	-4.5%	[-5.9%, -2.7%]	6
All ❌✅ (primary)	1.2%	[-0.9%, 2.8%]	5

Cycles

Results (primary 11.0%, 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)	11.0%	[2.2%, 28.4%]	13
Regressions ❌ (secondary)	4.8%	[2.2%, 9.7%]	3
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-3.5%	[-3.5%, -3.5%]	1
All ❌✅ (primary)	11.0%	[2.2%, 28.4%]	13

Binary size

Results (primary -0.1%, 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)	0.2%	[0.2%, 0.2%]	4
Regressions ❌ (secondary)	-	-	0
Improvements ✅ (primary)	-0.3%	[-0.3%, -0.3%]	4
Improvements ✅ (secondary)	-0.3%	[-0.3%, -0.3%]	4
All ❌✅ (primary)	-0.1%	[-0.3%, 0.2%]	8

Bootstrap: 489.575s -> 491.192s (0.33%)
Artifact size: 406.37 MiB -> 407.23 MiB (0.21%)

Kobzol · 2026-09-30T09:34:34Z

Pretty nice results!

aerooneqq · 2026-09-30T11:42:23Z

Parallelization of AST -> HIR lowering broke deterministic encoding of syntax contexts 🤣 (#161450).
UPD: not that sure about that, maybe some other parts of metadata causing it, will research it.

petrochenkov · 2026-09-30T11:47:14Z

@bors try @rust-timer queue

Parallelize AST -> HIR lowering

rust-bors · 2026-09-30T12:48:09Z

☀️ Try build successful (CI)
Build commit: 335f660 (335f660f9c0a0a3b69b6e32858af6d7f3af36c51)
Base parent: 7d2cd0f (7d2cd0fbc092625ea371da704f15f80216d2220e)

rust-timer · 2026-09-30T16:57:58Z

Finished benchmarking commit (335f660): comparison URL.

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

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.

Next, please: If you can, justify the regressions found in this try perf run in writing along with @rustbot label: +perf-regression-triaged. If not, fix the regressions and do another perf run. Neutral or positive results will clear the label automatically.

@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)	0.7%	[0.2%, 1.1%]	9
Regressions ❌ (secondary)	-	-	0
Improvements ✅ (primary)	-0.7%	[-0.8%, -0.7%]	2
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	0.4%	[-0.8%, 1.1%]	11

Max RSS (memory usage)

Results (primary -3.1%, 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)	1.8%	[1.8%, 1.8%]	1
Regressions ❌ (secondary)	2.1%	[2.0%, 2.2%]	2
Improvements ✅ (primary)	-3.1%	[-7.8%, -1.2%]	118
Improvements ✅ (secondary)	-3.1%	[-5.2%, -1.4%]	23
All ❌✅ (primary)	-3.1%	[-7.8%, 1.8%]	119

Cycles

Results (primary 14.6%, 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)	14.6%	[4.4%, 27.7%]	9
Regressions ❌ (secondary)	-	-	0
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-2.7%	[-3.0%, -2.5%]	3
All ❌✅ (primary)	14.6%	[4.4%, 27.7%]	9

Binary size

Results (primary -0.0%, secondary -0.1%)

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)	-	-	0
Improvements ✅ (primary)	-0.0%	[-0.1%, -0.0%]	9
Improvements ✅ (secondary)	-0.1%	[-0.1%, -0.1%]	5
All ❌✅ (primary)	-0.0%	[-0.1%, -0.0%]	9

Bootstrap: 489.84s -> 488.516s (-0.27%)
Artifact size: 406.54 MiB -> 406.46 MiB (-0.02%)

Kobzol · 2026-10-21T12:13:39Z

bors try rust-timer queue

Note that we have to gather the parent benchmark results first, so it only makes sense to do a perf. run here for the new benchmark configurations after the next PR merges into main.

aerooneqq · 2026-10-21T12:21:15Z

@bors try cancel

petrochenkov · 2026-10-21T12:21:18Z

In any case let's block this on #162848.
@rustbot blocked

rust-bors · 2026-10-21T12:21:20Z

Try build cancelled. Cancelled workflows:

https://github.com/rust-lang/rust/actions/runs/39595709798

Hint: if you want to run another try build, you do not need to manually cancel the previous one. Just run @bors try and bors will cancel the previous build automatically.

aerooneqq · 2026-10-21T15:49:38Z

@bors try @rust-timer queue

Parallelize AST -> HIR lowering

rust-bors · 2026-10-21T17:07:31Z

☀️ Try build successful (CI)
Build commit: 5e0645b (5e0645ba0af774ffb0502a41652ae5e7208b6381)
Base parent: 6a58677 (6a58677913ae3e443146503de3933abef0b2eda3)

rust-timer · 2026-10-21T17:57:29Z

Finished benchmarking commit (5e0645b): comparison URL.

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

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

Next, please: If you can, justify the regressions found in this try perf run in writing along with @rustbot label: +perf-regression-triaged. If not, fix the regressions and do another perf run. Neutral or positive results will clear the label automatically.

@bors rollup=iffy 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)	0.4%	[0.3%, 0.7%]	8
Regressions ❌ (secondary)	-	-	0
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-0.6%	[-0.6%, -0.6%]	1
All ❌✅ (primary)	0.4%	[0.3%, 0.7%]	8

Max RSS (memory usage)

Results (primary 0.9%, 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)	1.6%	[0.4%, 3.1%]	22
Regressions ❌ (secondary)	2.2%	[0.5%, 5.5%]	7
Improvements ✅ (primary)	-1.2%	[-2.5%, -0.6%]	7
Improvements ✅ (secondary)	-2.7%	[-4.9%, -1.3%]	3
All ❌✅ (primary)	0.9%	[-2.5%, 3.1%]	29

Cycles

Results (primary 3.2%, secondary -0.1%)

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

	mean	range	count
Regressions ❌ (primary)	3.8%	[0.4%, 9.7%]	32
Regressions ❌ (secondary)	1.3%	[0.9%, 1.9%]	4
Improvements ✅ (primary)	-2.4%	[-3.2%, -0.7%]	4
Improvements ✅ (secondary)	-1.1%	[-2.5%, -0.5%]	6
All ❌✅ (primary)	3.2%	[-3.2%, 9.7%]	36

Binary size

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

Bootstrap: 488.496s -> 491.134s (0.54%)
Artifact size: 406.57 MiB -> 406.46 MiB (-0.03%)

aerooneqq · 2026-10-22T10:55:13Z

@bors try @rust-timer queue

Parallelize AST -> HIR lowering

rust-bors · 2026-10-22T11:53:33Z

☀️ Try build successful (CI)
Build commit: 02b947e (02b947e39b782ed5ab7e1ae86fe43c274a41ce14)
Base parent: f8125e4 (f8125e48dc669320b4e5e83487dcbfb681957961)

rust-timer · 2026-10-22T13:10:31Z

Finished benchmarking commit (02b947e): comparison URL.

Overall result: ❌ regressions - please read:

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

Next, please: If you can, justify the regressions found in this try perf run in writing along with @rustbot label: +perf-regression-triaged. If not, fix the regressions and do another perf run. Neutral or positive results will clear the label automatically.

@bors rollup=iffy 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)	0.6%	[0.2%, 1.2%]	18
Regressions ❌ (secondary)	-	-	0
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	0.6%	[0.2%, 1.2%]	18

Max RSS (memory usage)

Results (primary 1.5%, 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)	1.6%	[0.6%, 3.2%]	21
Regressions ❌ (secondary)	2.5%	[1.5%, 5.3%]	4
Improvements ✅ (primary)	-0.4%	[-0.4%, -0.4%]	1
Improvements ✅ (secondary)	-3.3%	[-4.7%, -2.1%]	3
All ❌✅ (primary)	1.5%	[-0.4%, 3.2%]	22

Cycles

Results (primary 4.1%, 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)	4.9%	[0.8%, 11.7%]	25
Regressions ❌ (secondary)	1.7%	[0.5%, 4.6%]	6
Improvements ✅ (primary)	-0.7%	[-0.9%, -0.6%]	4
Improvements ✅ (secondary)	-2.5%	[-7.1%, -0.4%]	8
All ❌✅ (primary)	4.1%	[-0.9%, 11.7%]	29

Binary size

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

Bootstrap: 485.551s -> 488.779s (0.66%)
Artifact size: 406.38 MiB -> 406.44 MiB (0.02%)

This reverts commit 79e0cba.

rustbot assigned petrochenkov Sep 29, 2026

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 29, 2026

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rust-bors Bot pushed a commit that referenced this pull request Sep 29, 2026

Auto merge of #163495 - aerooneqq:parallel-ast-hir-lowering, r=<try>

79a91eb

Parallelize AST -> HIR lowering

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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 Sep 29, 2026

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

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

Auto merge of #163495 - aerooneqq:parallel-ast-hir-lowering, r=<try>

335f660

Parallelize AST -> HIR lowering

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

oli-obk self-assigned this Oct 2, 2026

This was referenced Oct 2, 2026

Remap syntax contexts and expansion ids for det. metadata encoding #163668

Merged

Remove NonOwner variant from AstOwner #163887

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petrochenkov added the S-waiting-on-author Status: This is awaiting some action (such as code changes or more information) from the author. label Oct 21, 2026

rustbot added S-blocked Status: Blocked on something else such as an RFC or other implementation work. and removed S-waiting-on-author Status: This is awaiting some action (such as code changes or more information) from the author. labels Oct 21, 2026

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rust-bors Bot pushed a commit that referenced this pull request Oct 21, 2026

Auto merge of #163495 - aerooneqq:parallel-ast-hir-lowering, r=<try>

5e0645b

Parallelize AST -> HIR lowering

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rustbot removed the S-waiting-on-perf Status: Waiting on a perf run to be completed. label Oct 21, 2026

Try to remove filter for non-owners

79e0cba

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rustbot added the S-waiting-on-perf Status: Waiting on a perf run to be completed. label Oct 22, 2026

rust-bors Bot pushed a commit that referenced this pull request Oct 22, 2026

Auto merge of #163495 - aerooneqq:parallel-ast-hir-lowering, r=<try>

02b947e

Parallelize AST -> HIR lowering

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rustbot removed the S-waiting-on-perf Status: Waiting on a perf run to be completed. label Oct 22, 2026

aerooneqq added 2 commits October 22, 2026 16:33

Revert "Try to remove filter for non-owners"

f9a5e17

This reverts commit 79e0cba.

Add comment about checking for non-owners

82a896e

oli-obk reviewed Oct 22, 2026

View reviewed changes

Comment thread compiler/rustc_data_structures/src/sync/parallel.rs

Comment thread compiler/rustc_interface/src/passes.rs Outdated

Move commit_end_of_determinism closer to parallel loop

1a6e8cb

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rust-timer commented Sep 29, 2026

Overall result: ❌ regressions - please read:

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

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

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Overall result: ❌ regressions - please read:

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