re-use `Sized` fast-path #139577

davidtwco · 2025-04-09T10:57:34Z

There's an existing fast path for the type_op_prove_predicate predicate, checking for trivially Sized types, which can be re-used when evaluating obligations within queries. This should improve performance and was found to be beneficial in #137944.

r? types

There's an existing fast path for the `type_op_prove_predicate` predicate, checking for trivially `Sized` types, which can be re-used when evaluating obligations within queries. This should improve performance, particularly in anticipation of new sizedness traits being added which can take advantage of this.

davidtwco · 2025-04-09T12:14:43Z

@bors try

re-use `Sized` fast-path There's an existing fast path for the `type_op_prove_predicate` predicate, checking for trivially `Sized` types, which can be re-used when evaluating obligations within queries. This should improve performance and was found to be beneficial in rust-lang#137944. r? types

bors · 2025-04-09T12:15:56Z

⌛ Trying commit 72d17bf with merge de946b5...

lqd · 2025-04-09T14:01:36Z

@rust-timer queue

bors · 2025-04-09T14:24:10Z

☀️ Try build successful - checks-actions
Build commit: de946b5 (de946b5221398ba73f5ee36a77f16c4f199c183f)

rust-timer · 2025-04-09T16:14:41Z

Finished benchmarking commit (de946b5): comparison URL.

Overall result: ✅ improvements - no action needed

Benchmarking this pull request likely means that it is perf-sensitive, so we're automatically marking it as not fit for rolling up. While you can manually mark this PR as fit for rollup, we strongly recommend not doing so since this PR may lead to changes in compiler perf.

@bors rollup=never
@rustbot label: -S-waiting-on-perf -perf-regression

Instruction count

This is the most reliable metric that we have; it was used to determine the overall result at the top of this comment. However, even this metric can sometimes exhibit noise.

	mean	range	count
Regressions ❌ (primary)	-	-	0
Regressions ❌ (secondary)	-	-	0
Improvements ✅ (primary)	-0.5%	[-1.2%, -0.2%]	73
Improvements ✅ (secondary)	-1.8%	[-12.1%, -0.1%]	55
All ❌✅ (primary)	-0.5%	[-1.2%, -0.2%]	73

Max RSS (memory usage)

Results (primary -1.9%, secondary 0.4%)

This is a less reliable metric that may be of interest but was not used to determine the overall result at the top of this comment.

	mean	range	count
Regressions ❌ (primary)	6.6%	[6.6%, 6.6%]	1
Regressions ❌ (secondary)	3.1%	[1.0%, 4.5%]	5
Improvements ✅ (primary)	-2.5%	[-8.2%, -0.5%]	15
Improvements ✅ (secondary)	-6.5%	[-7.4%, -5.6%]	2
All ❌✅ (primary)	-1.9%	[-8.2%, 6.6%]	16

Cycles

Results (primary -1.0%, secondary -3.9%)

This is a less reliable metric that may be of interest but was not used to determine the overall result at the top of this comment.

	mean	range	count
Regressions ❌ (primary)	-	-	0
Regressions ❌ (secondary)	-	-	0
Improvements ✅ (primary)	-1.0%	[-1.1%, -0.9%]	2
Improvements ✅ (secondary)	-3.9%	[-11.1%, -1.6%]	11
All ❌✅ (primary)	-1.0%	[-1.1%, -0.9%]	2

Binary size

This benchmark run did not return any relevant results for this metric.

Bootstrap: 779.721s -> 778.291s (-0.18%)
Artifact size: 366.13 MiB -> 366.06 MiB (-0.02%)

oli-obk · 2025-04-14T14:15:10Z

compiler/rustc_trait_selection/src/traits/util.rs

@@ -504,3 +505,21 @@ impl<'tcx> TypeFolder<TyCtxt<'tcx>> for PlaceholderReplacer<'_, 'tcx> {
        }
    }
 }
+
+pub fn sizedness_fast_path<'tcx>(tcx: TyCtxt<'tcx>, predicate: ty::Predicate<'tcx>) -> bool {


Maybe name it is_sized_pred_for_trivially_sized_type?

I didn't name it that because I add to it later in the Sized work with MetaSized and "we have a MetaSized predicate that we can skip because there's a Sized predicate with the same self_ty in the ParamEnv" - I can rename it in this PR as you suggest, and then rename it back to something more general later if you want?

hmm... I guess. It's nonobvious enough that you need to read the function anyway unless you already know what it is, then the name is unique enough.

oli-obk · 2025-04-14T14:16:16Z

tests/ui/closures/issue-78720.stderr

+LL | fn server() -> impl {
+   |                ^^^^ cannot infer type


lmao is this the {error type}: Sized fast path?

oli-obk

r=me with function renamed

oli-obk · 2025-04-14T14:25:39Z

@bors r+

bors · 2025-04-14T14:25:42Z

📌 Commit 72d17bf has been approved by oli-obk

It is now in the queue for this repository.

bors · 2025-04-14T19:54:31Z

⌛ Testing commit 72d17bf with merge 2da29db...

bors · 2025-04-14T23:04:39Z

☀️ Test successful - checks-actions
Approved by: oli-obk
Pushing 2da29db to master...

github-actions · 2025-04-14T23:06:43Z

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 990039e (parent) -> 2da29db (this PR)

Test differences

Show 6 test diffs

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

Job duration changes

x86_64-apple-2: 6457.7s -> 3952.7s (-38.8%)
dist-x86_64-apple: 7629.4s -> 9267.1s (21.5%)
dist-apple-various: 6999.1s -> 8156.3s (16.5%)
dist-aarch64-apple: 5612.8s -> 4932.6s (-12.1%)
x86_64-apple-1: 9100.0s -> 8246.2s (-9.4%)
x86_64-mingw-2: 7383.7s -> 6831.3s (-7.5%)
dist-x86_64-linux-alt: 7051.7s -> 7549.3s (7.1%)
x86_64-msvc-ext1: 7178.1s -> 7632.5s (6.3%)
x86_64-gnu-distcheck: 4809.7s -> 5081.9s (5.7%)
dist-android: 2536.5s -> 2663.2s (5.0%)

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 · 2025-04-15T01:35:14Z

Finished benchmarking commit (2da29db): comparison URL.

Overall result: ✅ improvements - no action needed

@rustbot label: -perf-regression

Instruction count

This is the most reliable metric that we have; it was used to determine the overall result at the top of this comment. However, even this metric can sometimes exhibit noise.

	mean	range	count
Regressions ❌ (primary)	-	-	0
Regressions ❌ (secondary)	-	-	0
Improvements ✅ (primary)	-0.6%	[-1.2%, -0.3%]	55
Improvements ✅ (secondary)	-2.1%	[-12.2%, -0.4%]	44
All ❌✅ (primary)	-0.6%	[-1.2%, -0.3%]	55

Max RSS (memory usage)

Results (primary -1.1%, secondary 0.4%)

This is a less reliable metric that may be of interest but was not used to determine the overall result at the top of this comment.

	mean	range	count
Regressions ❌ (primary)	1.3%	[0.4%, 2.3%]	2
Regressions ❌ (secondary)	2.9%	[2.8%, 3.0%]	2
Improvements ✅ (primary)	-1.6%	[-3.0%, -0.4%]	9
Improvements ✅ (secondary)	-2.2%	[-2.3%, -2.0%]	2
All ❌✅ (primary)	-1.1%	[-3.0%, 2.3%]	11

Cycles

Results (primary -0.6%, secondary -3.6%)

This is a less reliable metric that may be of interest but was not used to determine the overall result at the top of this comment.

	mean	range	count
Regressions ❌ (primary)	-	-	0
Regressions ❌ (secondary)	2.1%	[2.1%, 2.1%]	1
Improvements ✅ (primary)	-0.6%	[-0.6%, -0.6%]	1
Improvements ✅ (secondary)	-4.2%	[-10.6%, -2.0%]	10
All ❌✅ (primary)	-0.6%	[-0.6%, -0.6%]	1

Binary size

This benchmark run did not return any relevant results for this metric.

Bootstrap: 781.448s -> 781.17s (-0.04%)
Artifact size: 365.12 MiB -> 365.07 MiB (-0.01%)

rustbot assigned BoxyUwU Apr 9, 2025

rustbot added S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. T-compiler Relevant to the compiler team, which will review and decide on the PR/issue. labels Apr 9, 2025

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rustbot removed the S-waiting-on-perf Status: Waiting on a perf run to be completed. label Apr 9, 2025

davidtwco added a commit to davidtwco/rust that referenced this pull request Apr 10, 2025

upstream: rust-lang#139577

c258473

davidtwco added a commit to davidtwco/rust that referenced this pull request Apr 14, 2025

upstream: rust-lang#139577

7c1d2ff

oli-obk reviewed Apr 14, 2025

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oli-obk approved these changes Apr 14, 2025

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oli-obk assigned oli-obk and unassigned BoxyUwU Apr 14, 2025

bors 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 Apr 14, 2025

bors added the merged-by-bors This PR was explicitly merged by bors. label Apr 14, 2025

bors merged commit 2da29db into rust-lang:master Apr 14, 2025
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rustbot added this to the 1.88.0 milestone Apr 14, 2025

davidtwco deleted the sizedness-go-vroom branch April 15, 2025 08:15

davidtwco mentioned this pull request Apr 15, 2025

Sized Hierarchy: Part I #137944

Open

matthiaskrgr mentioned this pull request Apr 21, 2025

ICE: invalid immediate for given destination place: value ScalarPair does not match ABI Scalar #140100

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re-use `Sized` fast-path #139577

re-use `Sized` fast-path #139577

davidtwco commented Apr 9, 2025

davidtwco commented Apr 9, 2025 •

edited

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rust-timer commented Apr 15, 2025

re-use Sized fast-path #139577

re-use Sized fast-path #139577

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davidtwco commented Apr 9, 2025

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Overall result: ✅ improvements - no action needed

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oli-obk commented Apr 14, 2025

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Test differences

Job duration changes

rust-timer commented Apr 15, 2025

Overall result: ✅ improvements - no action needed

re-use `Sized` fast-path #139577

re-use `Sized` fast-path #139577

davidtwco commented Apr 9, 2025 •

edited

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