Fast path nitpicks #143307

compiler-errors · 2025-07-02T00:38:38Z

Miscellaneous commits that I didn't really want to fold into anything else.

Fixes one theoretical bug with the fast path not considering polarity for T: !Sized bounds.

rustbot · 2025-07-02T00:38:43Z

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compiler-errors · 2025-07-02T00:39:00Z

compiler/rustc_traits/src/codegen.rs

@@ -34,13 +34,6 @@ pub(crate) fn codegen_select_candidate<'tcx>(
    let (infcx, param_env) = tcx.infer_ctxt().ignoring_regions().build_with_typing_env(typing_env);
    let mut selcx = SelectionContext::new(&infcx);

-    if sizedness_fast_path(tcx, trait_ref.upcast(tcx)) {


This function shouldn't ever be reached -- we never do Instance::resolve on Sized.

compiler-errors · 2025-07-02T00:39:59Z

@bors2 try @rust-timer queue

r? lcnr perhaps

rust-bors · 2025-07-02T00:40:03Z

⌛ Trying commit 91c53c9 with merge 227ec3b…

To cancel the try build, run the command @bors2 try cancel.

Fast path nitpicks Miscellaneous commits that I didn't really want to fold into anything else. Fixes one theoretical bug with the fast path not considering polarity for `T: !Sized` bounds.

rust-bors · 2025-07-02T02:57:12Z

☀️ Try build successful (CI)
Build commit: 227ec3b (227ec3b415808af85fe11410d8e1b4d8349c32bc, parent: 71e4c005caa812a16fcb08d0bf1e6f1eda7c8381)

lcnr · 2025-07-03T13:06:28Z

compiler/rustc_trait_selection/src/traits/util.rs

        predicate.kind().skip_binder()
+        && trait_pred.polarity == ty::PredicatePolarity::Positive


this has happened multiple times by now 🤔 forgetting the polarity is too damn easy right now 🤔

I can't really think of a good alternative apart from actually splitting ClauseKind::Trait and ClauseKind::NegTrait 🤔

removing the def_id etc functions on TraitPredicate to require trait_pred.trait_ref.def_id() instead feels really cumbersome and not that helpful 🤔 changing ClauseKind::Trait to have TraitRef and Polarity as separate fields so that we always have to use (_, _) could work but feels really ugly

anyways, not part of this PR

lcnr · 2025-07-03T13:07:00Z

@rust-timer build 227ec3b

lcnr · 2025-07-03T13:07:48Z

r=me after getting perf to work ☠️

rust-timer · 2025-07-03T13:19:27Z

Finished benchmarking commit (227ec3b): comparison URL.

Overall result: ✅ improvements - no action needed

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.

@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
Regressions ❌ (secondary)	-	-	0
Improvements ✅ (primary)	-0.2%	[-0.2%, -0.2%]	2
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	-0.2%	[-0.2%, -0.2%]	2

Max RSS (memory usage)

Results (primary -2.1%, secondary -2.0%)

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)	-2.1%	[-2.6%, -1.7%]	2
Improvements ✅ (secondary)	-2.0%	[-2.6%, -1.3%]	2
All ❌✅ (primary)	-2.1%	[-2.6%, -1.7%]	2

Cycles

Results (primary 0.3%, 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)	1.7%	[1.5%, 1.9%]	2
Regressions ❌ (secondary)	1.6%	[0.6%, 2.5%]	2
Improvements ✅ (primary)	-1.0%	[-1.1%, -1.0%]	2
Improvements ✅ (secondary)	-2.1%	[-2.1%, -2.1%]	1
All ❌✅ (primary)	0.3%	[-1.1%, 1.9%]	4

Binary size

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

Bootstrap: 463.343s -> 462.134s (-0.26%)
Artifact size: 372.24 MiB -> 372.24 MiB (-0.00%)

lcnr · 2025-07-03T14:26:49Z

@bors r+

bors · 2025-07-03T14:26:52Z

📌 Commit 91c53c9 has been approved by lcnr

It is now in the queue for this repository.

compiler-errors · 2025-07-03T19:46:31Z

@bors rollup

Rollup of 11 pull requests Successful merges: - #142749 (Add methods for converting bool to `Result<(), E>`) - #143288 (Fix `x clean` with a fifo) - #143307 (Fast path nitpicks) - #143346 (update coherence example) - #143356 (use unsigned_abs instead of `abs` on signed int to silence clippy) - #143370 (remove redundant #[must_use]) - #143378 (simplify receivers for some array method calls) - #143380 (Replace kw_span by full span for generic const parameters.) - #143381 (rustdoc: don't treat methods under const impls or traits as const) - #143394 (compiler: Document and reduce `fn provide`s in hir crates) - #143395 (Always use the pure Rust fallback instead of `llvm.{maximum,minimum}`) r? `@ghost` `@rustbot` modify labels: rollup

Rollup merge of #143307 - compiler-errors:fast-path-nitpicks, r=lcnr Fast path nitpicks Miscellaneous commits that I didn't really want to fold into anything else. Fixes one theoretical bug with the fast path not considering polarity for `T: !Sized` bounds.

Rollup of 11 pull requests Successful merges: - rust-lang/rust#142749 (Add methods for converting bool to `Result<(), E>`) - rust-lang/rust#143288 (Fix `x clean` with a fifo) - rust-lang/rust#143307 (Fast path nitpicks) - rust-lang/rust#143346 (update coherence example) - rust-lang/rust#143356 (use unsigned_abs instead of `abs` on signed int to silence clippy) - rust-lang/rust#143370 (remove redundant #[must_use]) - rust-lang/rust#143378 (simplify receivers for some array method calls) - rust-lang/rust#143380 (Replace kw_span by full span for generic const parameters.) - rust-lang/rust#143381 (rustdoc: don't treat methods under const impls or traits as const) - rust-lang/rust#143394 (compiler: Document and reduce `fn provide`s in hir crates) - rust-lang/rust#143395 (Always use the pure Rust fallback instead of `llvm.{maximum,minimum}`) r? `@ghost` `@rustbot` modify labels: rollup

compiler-errors added 3 commits July 2, 2025 00:33

Remove fast path from codegen_select, since Sized has no methods

ae0bef7

Use is_trivially_wf for ProvePredicate fast path

d3c0ef0

Consider polarity in sizedness fast path

91c53c9

rustbot assigned SparrowLii Jul 2, 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 Jul 2, 2025

compiler-errors commented Jul 2, 2025

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rustbot added the S-waiting-on-perf Status: Waiting on a perf run to be completed. label Jul 2, 2025

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lcnr reviewed Jul 3, 2025

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lcnr 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 Jul 3, 2025

rustbot removed the S-waiting-on-perf Status: Waiting on a perf run to be completed. label Jul 3, 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-author Status: This is awaiting some action (such as code changes or more information) from the author. labels Jul 3, 2025

jhpratt mentioned this pull request Jul 4, 2025

Rollup of 11 pull requests #143407

Merged

bors merged commit 9de211b into rust-lang:master Jul 4, 2025
10 checks passed

rustbot added this to the 1.90.0 milestone Jul 4, 2025

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Fast path nitpicks #143307

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		predicate.kind().skip_binder()
		&& trait_pred.polarity == ty::PredicatePolarity::Positive

Fast path nitpicks #143307

Fast path nitpicks #143307

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rust-timer commented Jul 3, 2025

Overall result: ✅ improvements - no action needed

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