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%)

rustbot · 2026-10-29T08:40:06Z

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

@bors r+

View changes since this review

rust-bors · 2026-10-29T11:23:13Z

📋 This PR cannot be approved because it currently has the following label: S-blocked.

petrochenkov · 2026-11-03T12:50:53Z

#162848 is getting delayed, so let's merge this one, it can be easily reverted if it causes issues.
@bors r=petrochenkov,oli-obk

rust-bors · 2026-11-03T12:50:57Z

📋 This PR cannot be approved because it currently has the following label: S-blocked.

petrochenkov · 2026-11-03T12:51:20Z

@bors r=petrochenkov,oli-obk

rust-bors · 2026-11-03T12:51:26Z

📌 Commit f7755c8 has been approved by petrochenkov,oli-obk

It is now in the queue for this repository.

@petrochenkov

…g, r=petrochenkov,oli-obk Parallelize AST -> HIR lowering Parallelize AST -> HIR lowering. r? @petrochenkov

…uwer Rollup of 20 pull requests Successful merges: - #149245 (Make inline attributes apply to the generated `poll` in async fn) - #163495 (Parallelize AST -> HIR lowering) - #164304 ([perf] Reuse CanonicalVarKinds if no new variables were added) - #165109 (Avoid building a region map when erasing bound regions) - #163393 (std: Use getexecpath() for current_exe() on OpenBSD) - #163625 (Add a lint helper attribute namespace ) - #164414 (Add `let_underscore_drop_guard` lint.) - #165342 (Avoid unnecessary MIR traversals in CheckPackedRef lint) - #165351 (delegation: insert probing adjustments before args check adjustments) - #165358 (Reenable some cg_gcc tests that were disabled) - #165377 (Make `no_implicit_prelude` not suppress tool attributes) - #165397 (Add codegen test for unused match arms removed after inlining) - #165398 (Rework parallel reproducibility tests) - #162608 (Avoid oscillating line wrapping due to symbol indices) - #164241 (make the safety documentation consistent in Ptr module) - #165029 (Use `MalformedLintAttributeInput` in more places) - #165203 (AIX: Implement TLS destructor guard in std and update dynamic-loading-cdylib test) - #165230 (Fix rigidity assertion ICE) - #165293 (unstable-book: update default-visibility.md to link to tracking issue) - #165374 (Refactorings in preparation for the move trait)

@petrochenkov

…g, r=petrochenkov,oli-obk Parallelize AST -> HIR lowering Parallelize AST -> HIR lowering. r? @petrochenkov

…uwer Rollup of 21 pull requests Successful merges: - #165416 (fix unsoundness when compiling `[diverging_const; 0]`) - #149245 (Make inline attributes apply to the generated `poll` in async fn) - #163495 (Parallelize AST -> HIR lowering) - #164304 ([perf] Reuse CanonicalVarKinds if no new variables were added) - #165109 (Avoid building a region map when erasing bound regions) - #163393 (std: Use getexecpath() for current_exe() on OpenBSD) - #163625 (Add a lint helper attribute namespace ) - #164414 (Add `let_underscore_drop_guard` lint.) - #165342 (Avoid unnecessary MIR traversals in CheckPackedRef lint) - #165351 (delegation: insert probing adjustments before args check adjustments) - #165358 (Reenable some cg_gcc tests that were disabled) - #165377 (Make `no_implicit_prelude` not suppress tool attributes) - #165397 (Add codegen test for unused match arms removed after inlining) - #165398 (Rework parallel reproducibility tests) - #162608 (Avoid oscillating line wrapping due to symbol indices) - #164241 (make the safety documentation consistent in Ptr module) - #165029 (Use `MalformedLintAttributeInput` in more places) - #165203 (AIX: Implement TLS destructor guard in std and update dynamic-loading-cdylib test) - #165230 (Fix rigidity assertion ICE) - #165293 (unstable-book: update default-visibility.md to link to tracking issue) - #165374 (Refactorings in preparation for the move trait)

@petrochenkov

…g, r=petrochenkov,oli-obk Parallelize AST -> HIR lowering Parallelize AST -> HIR lowering. r? @petrochenkov

…uwer Rollup of 20 pull requests Successful merges: - #149245 (Make inline attributes apply to the generated `poll` in async fn) - #163495 (Parallelize AST -> HIR lowering) - #164304 ([perf] Reuse CanonicalVarKinds if no new variables were added) - #165109 (Avoid building a region map when erasing bound regions) - #163393 (std: Use getexecpath() for current_exe() on OpenBSD) - #163625 (Add a lint helper attribute namespace ) - #164414 (Add `let_underscore_drop_guard` lint.) - #165342 (Avoid unnecessary MIR traversals in CheckPackedRef lint) - #165351 (delegation: insert probing adjustments before args check adjustments) - #165358 (Reenable some cg_gcc tests that were disabled) - #165377 (Make `no_implicit_prelude` not suppress tool attributes) - #165397 (Add codegen test for unused match arms removed after inlining) - #165398 (Rework parallel reproducibility tests) - #162608 (Avoid oscillating line wrapping due to symbol indices) - #164241 (make the safety documentation consistent in Ptr module) - #165029 (Use `MalformedLintAttributeInput` in more places) - #165203 (AIX: Implement TLS destructor guard in std and update dynamic-loading-cdylib test) - #165230 (Fix rigidity assertion ICE) - #165293 (unstable-book: update default-visibility.md to link to tracking issue) - #165374 (Refactorings in preparation for the move trait)

JonathanBrouwer · 2026-11-03T20:53:23Z

@bors try jobs=test-x86_64-gnu-parallel-frontend

Parallelize AST -> HIR lowering try-job: test-x86_64-gnu-parallel-frontend

JonathanBrouwer · 2026-11-03T21:09:40Z

💔 I suspect this PR failed tests as part of a rollup
@bors r-

After fixing the problem, consider running a try job for the failed job before re-approving.

Link to failure: #165426 (comment)

rust-bors · 2026-11-03T21:09:48Z

This pull request was unapproved.

This PR was contained in a rollup (#165426), which was unapproved.

View changes since this unapproval

rust-bors · 2026-11-03T22:14:18Z

💔 Test for 5863e56 failed: CI. Failed job:

try - test-x86_64-gnu-parallel-frontend (web logs, enhanced plaintext logs)

rustbot assigned petrochenkov 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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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

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

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Remove NonOwner variant from AstOwner #163887

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Parallelize AST -> HIR lowering

f7755c8

aerooneqq force-pushed the parallel-ast-hir-lowering branch from 9efc5bc to f7755c8 Compare October 29, 2026 08:41

oli-obk approved these changes Oct 29, 2026

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Rollup merge of rust-lang#163495 - aerooneqq:parallel-ast-hir-lowerin…

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…g, r=petrochenkov,oli-obk Parallelize AST -> HIR lowering Parallelize AST -> HIR lowering. r? @petrochenkov

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Rollup of 20 pull requests #165411

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Rollup merge of rust-lang#163495 - aerooneqq:parallel-ast-hir-lowerin…

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…g, r=petrochenkov,oli-obk Parallelize AST -> HIR lowering Parallelize AST -> HIR lowering. r? @petrochenkov

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Rollup of 21 pull requests #165418

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Rollup merge of rust-lang#163495 - aerooneqq:parallel-ast-hir-lowerin…

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…g, r=petrochenkov,oli-obk Parallelize AST -> HIR lowering Parallelize AST -> HIR lowering. r? @petrochenkov

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Rollup of 20 pull requests #165426

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

5863e56

Parallelize AST -> HIR lowering try-job: test-x86_64-gnu-parallel-frontend

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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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