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Skip walking into param-env component if it has no placeholder/re-var #143500

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Skip walking into param-env component if it has no placeholder/re-var #143500

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@compiler-errors compiler-errors commented Jul 5, 2025 •
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Although it only provides a minor perf improvement, it seems like it could matter in more pathological cases.

@rustbot rustbot added T-compiler Relevant to the compiler team, which will review and decide on the PR/issue. WG-trait-system-refactor The Rustc Trait System Refactor Initiative (-Znext-solver) labels Jul 5, 2025
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@bors2 try @rust-timer queue

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rust-bors bot commented Jul 5, 2025

⌛ Trying commit e13757e with merge e3ecd5f…

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

rust-bors bot added a commit that referenced this pull request Jul 5, 2025
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Auto merge of #143500 - compiler-errors:characterize-less, r=<try>
e3ecd5f 
[perf] Skip walking into param-env component if it has no placeholder/re-var
@rustbot rustbot added the S-waiting-on-perf Status: Waiting on a perf run to be completed. label Jul 5, 2025
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rust-bors bot commented Jul 5, 2025

☀️ Try build successful (CI)
Build commit: e3ecd5f (e3ecd5f5fd02f50bc278c1f0cd5b4dbd9e07242a, parent: 6dec76f1c2809fded082dd44d3752d3f6220d767)

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Finished benchmarking commit (e3ecd5f): comparison URL.

Overall result: ❌✅ regressions and 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)		 0.0% [0.0%, 0.0%] 1
Improvements ✅
(primary)		 - - 0
Improvements ✅
(secondary)		 -0.5% [-0.5%, -0.5%] 3
All ❌✅ (primary) - - 0

Max RSS (memory usage)

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

Cycles

Results (secondary 0.2%)

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)		 2.4% [2.4%, 2.4%] 1
Improvements ✅
(primary)		 - - 0
Improvements ✅
(secondary)		 -2.0% [-2.0%, -2.0%] 1
All ❌✅ (primary) - - 0

Binary size

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

Bootstrap: 461.008s -> 461.232s (0.05%)
Artifact size: 372.14 MiB -> 372.18 MiB (0.01%)

@rustbot rustbot removed the S-waiting-on-perf Status: Waiting on a perf run to be completed. label Jul 5, 2025
@compiler-errors compiler-errors changed the title [perf] Skip walking into param-env component if it has no placeholder/re-var Skip walking into param-env component if it has no placeholder/re-var Jul 6, 2025
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r? lcnr

@compiler-errors compiler-errors marked this pull request as ready for review July 6, 2025 17:18
@rustbot rustbot added the S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. label Jul 6, 2025
lcnr
lcnr reviewed Jul 7, 2025
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compiler/rustc_next_trait_solver/src/solve/assembly/mod.rs
@@ -1069,8 +1070,10 @@ where
} else {
ControlFlow::Continue(())
}
} else {
} else if ty.has_type_flags(TypeFlags::HAS_PLACEHOLDER | TypeFlags::HAS_RE_INFER) {
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why only RE_INFER instead of full infer?

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bc we only care about infer regions in this folder's logic -- it would not even be necessary if we didn't replace free regions with infer

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why would we care about ty/ct infer for this folder anyways? 🤔

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