Fancy paramenv accessors that communicate the access pattern better. by jdonszelmann · Pull Request #163477 · rust-lang/rust

jdonszelmann · 2026-09-29T09:47:19Z

r? @lcnr or @rust-lang/initiative-trait-system-refactor

This is a single commit, to precede the future change of "compressed trait clauses". It adds a lot of the infrastructure, without making any real changes that may affect performance. As such it forms a separately reviewable step. Even though this isn't on its own such a useful change, it mostly refactors things, it does still make for a nicer API surface.

Importantly, with compressed trait clauses (i.e. encoding some common traits as where self_ty : <bitset of common traits>), it becomes very important to be careful with how we iterate over caller bounds. I've tried other methods, but the typestate API (as proposed in this PR) is the only one I've found that's both ergonomic, and still allows for implementing compressed trait clauses performantly.

Note

I've not used an LLM for any part of this PR, or any other PR I make. This includes any related work like research.

jdonszelmann · 2026-11-02T14:40:00Z

r? project-trait-system-refactor

rustbot · 2026-11-02T14:40:05Z

Some changes occurred to MIR optimizations

cc @rust-lang/wg-mir-opt

Some changes occurred in const_evaluatable.rs

cc @BoxyUwU

rustbot · 2026-11-02T19:46:54Z

clippy is developed in its own repository. If possible, consider making this change to rust-lang/rust-clippy instead.

cc @rust-lang/clippy

jdonszelmann · 2026-11-03T12:44:48Z

r? @ShoyuVanilla

ShoyuVanilla · 2026-11-04T04:06:17Z

Let me check the perf, just in case 😄
@bors try @rust-timer queue

jdonszelmann · 2026-11-04T12:58:48Z

@bors try @rust-timer queue

Fancy paramenv accessors that communicate the access pattern better.

rust-bors · 2026-11-04T13:57:12Z

☀️ Try build successful (CI)
Build commit: aa31ab2 (aa31ab2e728749c5c049528aabf370438d86507d)
Base parent: 2d20b42 (2d20b42b883dcfc014f3c2c56081eeb6091c2179)

rust-timer · 2026-11-04T14:46:14Z

Finished benchmarking commit (aa31ab2): 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)	0.8%	[0.5%, 1.3%]	16
Regressions ❌ (secondary)	-	-	0
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	0.8%	[0.5%, 1.3%]	16

Max RSS (memory usage)

Results (primary -0.5%, 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)	2.8%	[2.3%, 3.2%]	2
Regressions ❌ (secondary)	2.2%	[2.2%, 2.2%]	1
Improvements ✅ (primary)	-3.8%	[-6.3%, -1.3%]	2
Improvements ✅ (secondary)	-3.1%	[-3.1%, -3.1%]	1
All ❌✅ (primary)	-0.5%	[-6.3%, 3.2%]	4

Cycles

Results (primary 2.7%)

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

	mean	range	count
Regressions ❌ (primary)	2.7%	[2.3%, 3.0%]	6
Regressions ❌ (secondary)	-	-	0
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	2.7%	[2.3%, 3.0%]	6

Binary size

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

Bootstrap: 480.462s -> 481.851s (0.29%)
Artifact size: 406.22 MiB -> 406.32 MiB (0.02%)

jdonszelmann · 2026-11-04T14:52:21Z

smol regressions, unfortunate but I'll keep working on those in subsequent PRs. Without this change more changes are impossible, and I do not wish to ask someone to review this PR together with subtler changes.

@bors r=ShoyuVanilla

rust-bors · 2026-11-04T14:52:27Z

📌 Commit 08fe89e has been approved by ShoyuVanilla

It is now in the queue for this repository.

ShoyuVanilla · 2026-11-04T15:05:12Z

Interesting. The regressed benchmarks have next-solver counterparts but they aren't regressed 🤔

jdonszelmann · 2026-11-04T16:03:41Z

yea that makes sense, in the next solver I already in this PR use slightly more specific accessors that probably perform a little better

@lcnr

…=ShoyuVanilla Fancy paramenv accessors that communicate the access pattern better. r? @lcnr or @rust-lang/initiative-trait-system-refactor This is a single commit, to precede the future change of "compressed trait clauses". It adds a lot of the infrastructure, without making any real changes that may affect performance. As such it forms a separately reviewable step. Even though this isn't on its own such a useful change, it mostly refactors things, it does still make for a nicer API surface. Importantly, with compressed trait clauses (i.e. encoding some common traits as `where self_ty : <bitset of common traits>`), it becomes very important to be careful with how we iterate over caller bounds. I've tried other methods, but the typestate API (as proposed in this PR) is the only one I've found that's both ergonomic, and still allows for implementing compressed trait clauses performantly. > [!NOTE] > I've not used an LLM for any part of this PR, or any other PR I make. This includes any related work like research.

@lcnr

…=ShoyuVanilla Fancy paramenv accessors that communicate the access pattern better. r? @lcnr or @rust-lang/initiative-trait-system-refactor This is a single commit, to precede the future change of "compressed trait clauses". It adds a lot of the infrastructure, without making any real changes that may affect performance. As such it forms a separately reviewable step. Even though this isn't on its own such a useful change, it mostly refactors things, it does still make for a nicer API surface. Importantly, with compressed trait clauses (i.e. encoding some common traits as `where self_ty : <bitset of common traits>`), it becomes very important to be careful with how we iterate over caller bounds. I've tried other methods, but the typestate API (as proposed in this PR) is the only one I've found that's both ergonomic, and still allows for implementing compressed trait clauses performantly. > [!NOTE] > I've not used an LLM for any part of this PR, or any other PR I make. This includes any related work like research.

ShoyuVanilla · 2026-11-05T04:45:47Z

Yeah, I saw them and actually expected that this could be a perf improvement because of them, but looks like we have some subtlties that regressing this. But given that your fine grained accesses negates them and you are going to improve this further the perf regressions feel okayish to me (anyway, we are gonna deprecate the old solver eventually 😁)

Rollup of 13 pull requests Successful merges: - #163477 (Fancy paramenv accessors that communicate the access pattern better.) - #160593 (turn ABI-controlling target features into a target modifier) - #164896 (offload: pass the linked device image to the host pass) - #165468 (Remove return type from `BuilderMethods::store`) - #159374 (Lower #[no_mangle] to #[symbol_name]/#[link_name]) - #164564 (Re-enable outline-atomics by default on more AArch64 platforms) - #164623 (add next-solver regression tests for two fixed ices) - #164678 (add next-solver regression test for recursive opaque ICE under validate-mir) - #165429 (Add tests for `-Zcrate-attr` edition and position) - #165430 ([tiny] Show context for found assoc item in E0107) - #165456 (std: Fix build for the L4Re targets) - #165463 (Add BTreeMap::allocator and BTreeSet::allocator) - #165466 (Don't "exit" using `panic` on teeos)

Rollup of 15 pull requests Successful merges: - #163477 (Fancy paramenv accessors that communicate the access pattern better.) - #160593 (turn ABI-controlling target features into a target modifier) - #164896 (offload: pass the linked device image to the host pass) - #165468 (Remove return type from `BuilderMethods::store`) - #164564 (Re-enable outline-atomics by default on more AArch64 platforms) - #164623 (add next-solver regression tests for two fixed ices) - #164653 (Deprecate internal function `vec::from_elem`) - #164678 (add next-solver regression test for recursive opaque ICE under validate-mir) - #165387 (windows OpenOptionsExt examples: replace winapi by windows crate) - #165429 (Add tests for `-Zcrate-attr` edition and position) - #165430 ([tiny] Show context for found assoc item in E0107) - #165456 (std: Fix build for the L4Re targets) - #165463 (Add BTreeMap::allocator and BTreeSet::allocator) - #165466 (Don't "exit" using `panic` on teeos) - #165491 (Remove unused compiler types and associated helpers)

@lcnr

Rollup merge of #163477 - jdonszelmann:paramenv-accessors, r=ShoyuVanilla Fancy paramenv accessors that communicate the access pattern better. r? @lcnr or @rust-lang/initiative-trait-system-refactor This is a single commit, to precede the future change of "compressed trait clauses". It adds a lot of the infrastructure, without making any real changes that may affect performance. As such it forms a separately reviewable step. Even though this isn't on its own such a useful change, it mostly refactors things, it does still make for a nicer API surface. Importantly, with compressed trait clauses (i.e. encoding some common traits as `where self_ty : <bitset of common traits>`), it becomes very important to be careful with how we iterate over caller bounds. I've tried other methods, but the typestate API (as proposed in this PR) is the only one I've found that's both ergonomic, and still allows for implementing compressed trait clauses performantly. > [!NOTE] > I've not used an LLM for any part of this PR, or any other PR I make. This includes any related work like research.

rust-timer · 2026-11-05T16:10:48Z

Note

This PR was benchmarked as part of triage of its containing rollup: triage URL.

Finished benchmarking commit (68cd6ad): 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%	[0.2%, 1.3%]	17
Regressions ❌ (secondary)	-	-	0
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	0.8%	[0.2%, 1.3%]	17

Max RSS (memory usage)

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

Cycles

Results (primary 2.7%)

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

	mean	range	count
Regressions ❌ (primary)	2.7%	[2.4%, 2.9%]	5
Regressions ❌ (secondary)	-	-	0
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	2.7%	[2.4%, 2.9%]	5

Binary size

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

Artifact size: 406.29 MiB -> 406.33 MiB (0.01%)

rustbot assigned lcnr Sep 29, 2026

jdonszelmann force-pushed the paramenv-accessors branch 3 times, most recently from 6d71f6c to 82b91b0 Compare September 29, 2026 13:07

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jdonszelmann force-pushed the paramenv-accessors branch from 82b91b0 to b45b7bd Compare November 2, 2026 14:35

rustbot added the T-bootstrap Relevant to the bootstrap subteam: Rust's build system (x.py and src/bootstrap) label Nov 2, 2026

jdonszelmann force-pushed the paramenv-accessors branch from b45b7bd to d7aa906 Compare November 2, 2026 14:39

jdonszelmann marked this pull request as ready for review November 2, 2026 14:40

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jdonszelmann added 2 commits November 4, 2026 13:58

Fancy paramenv accessors that communicate the access pattern better.

a5310be

rustdoc and clippy

08fe89e

jdonszelmann force-pushed the paramenv-accessors branch from d368c73 to 08fe89e Compare November 4, 2026 12:58

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rust-bors Bot pushed a commit that referenced this pull request Nov 4, 2026

Auto merge of #163477 - jdonszelmann:paramenv-accessors, r=<try>

aa31ab2

Fancy paramenv accessors that communicate the access pattern better.

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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 Nov 4, 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 Nov 4, 2026

jhpratt mentioned this pull request Nov 5, 2026

Rollup of 12 pull requests #165480

Closed

jhpratt mentioned this pull request Nov 5, 2026

Rollup of 13 pull requests #165488

Closed

jhpratt mentioned this pull request Nov 5, 2026

Rollup of 15 pull requests #165493

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rust-bors Bot merged commit 8baab12 into rust-lang:main Nov 5, 2026
15 checks passed

rustbot added this to the 1.101.0 milestone Nov 5, 2026

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Overall result: ❌ regressions - please read:

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Overall result: ❌ regressions - please read:

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