Match on lang item kind instead of using an if/else chain #140386

oli-obk · 2025-04-28T09:09:12Z

Similar to how the new solver does this. Just noticed while I was adding a new entry to the chain 😆

oli-obk · 2025-04-28T09:09:21Z

@bors try @rust-timer queue

…try> Match on lang item kind instead of using an if/else chain r? `@ghost`

bors · 2025-04-28T09:10:44Z

⌛ Trying commit 7454d4c with merge 4ef08a1...

bors · 2025-04-28T11:20:38Z

☀️ Try build successful - checks-actions
Build commit: 4ef08a1 (4ef08a1befdf4932d9a8347d7a318b04930aa148)

Kobzol · 2025-04-28T11:28:18Z

Could also make sense to order these by frequency of occurrence, although PGO might already do that.

rust-timer · 2025-04-28T12:50:35Z

Finished benchmarking commit (4ef08a1): 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)	-0.4%	[-0.8%, -0.2%]	38
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	-0.4%	[-0.8%, -0.2%]	38

Max RSS (memory usage)

Results (primary 0.9%, secondary 3.0%)

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)	0.9%	[0.4%, 3.1%]	16
Regressions ❌ (secondary)	3.0%	[2.8%, 3.2%]	2
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	0.9%	[0.4%, 3.1%]	16

Cycles

Results (primary -0.6%)

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)	-	-	0
Improvements ✅ (primary)	-0.6%	[-0.7%, -0.5%]	3
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	-0.6%	[-0.7%, -0.5%]	3

Binary size

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

Bootstrap: 761.588s -> 762.112s (0.07%)
Artifact size: 365.21 MiB -> 365.01 MiB (-0.05%)

oli-obk · 2025-04-28T13:38:40Z

@bors try @rust-timer queue

bors · 2025-04-28T13:39:50Z

⌛ Trying commit 7d3e707 with merge 2658a39b26bea05b2383c33dce1cbcd22491e4cf...

…try> Match on lang item kind instead of using an if/else chain r? `@ghost`

compiler-errors · 2025-04-28T14:50:02Z

compiler/rustc_trait_selection/src/traits/select/candidate_assembly.rs

-                    self.assemble_builtin_bound_candidates(clone_conditions, &mut candidates);
+            let lang_item = tcx.as_lang_item(def_id);
+            match lang_item {
+                Some(LangItem::Copy) => {


Merge this Copy with the Clone branch below. The behavior should be the same.

compiler-errors · 2025-04-28T14:50:24Z

compiler/rustc_trait_selection/src/traits/select/candidate_assembly.rs

+                    );
+                }
+                _ => {
+                    match lang_item {


Add a note that we re-match here to deal with the fallthrough case of assembling impl candidates for these user-implementable builtin traits.

bors · 2025-04-28T15:46:39Z

☀️ Try build successful - checks-actions
Build commit: 2658a39 (2658a39b26bea05b2383c33dce1cbcd22491e4cf)

rust-timer · 2025-04-28T18:46:49Z

Finished benchmarking commit (2658a39): comparison URL.

Overall result: ❌✅ regressions and improvements - please read the text below

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.

Next Steps: If you can justify the regressions found in this try perf run, please indicate this with @rustbot label: +perf-regression-triaged along with sufficient written justification. If you cannot justify the regressions please fix the regressions and do another perf run. If the next run shows neutral or positive results, the label will be automatically removed.

@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)	2.9%	[2.9%, 2.9%]	1
Regressions ❌ (secondary)	-	-	0
Improvements ✅ (primary)	-0.4%	[-0.8%, -0.2%]	36
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	-0.3%	[-0.8%, 2.9%]	37

Max RSS (memory usage)

Results (primary 0.1%)

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)	0.7%	[0.5%, 0.9%]	2
Regressions ❌ (secondary)	-	-	0
Improvements ✅ (primary)	-0.6%	[-0.6%, -0.6%]	2
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	0.1%	[-0.6%, 0.9%]	4

Cycles

Results (primary 0.1%)

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)	1.8%	[0.5%, 3.1%]	2
Regressions ❌ (secondary)	-	-	0
Improvements ✅ (primary)	-0.6%	[-0.7%, -0.5%]	5
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	0.1%	[-0.7%, 3.1%]	7

Binary size

Results (primary 1.1%)

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)	1.1%	[1.1%, 1.1%]	1
Regressions ❌ (secondary)	-	-	0
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	1.1%	[1.1%, 1.1%]	1

Bootstrap: 761.378s -> 762.587s (0.16%)
Artifact size: 365.18 MiB -> 365.02 MiB (-0.04%)

oli-obk added 2 commits April 28, 2025 09:00

Replace if/elseif chain with match

d48aa8e

Always check the lang item first

7454d4c

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 28, 2025

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rustbot added the S-waiting-on-perf Status: Waiting on a perf run to be completed. label Apr 28, 2025

bors added a commit to rust-lang-ci/rust that referenced this pull request Apr 28, 2025

Auto merge of rust-lang#140386 - oli-obk:match-on-lang-item-kind, r=<…

4ef08a1

…try> Match on lang item kind instead of using an if/else chain r? `@ghost`

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rustbot removed the S-waiting-on-perf Status: Waiting on a perf run to be completed. label Apr 28, 2025

Also match on the lang item in confirmation

7d3e707

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rustbot added the S-waiting-on-perf Status: Waiting on a perf run to be completed. label Apr 28, 2025

bors added a commit to rust-lang-ci/rust that referenced this pull request Apr 28, 2025

Auto merge of rust-lang#140386 - oli-obk:match-on-lang-item-kind, r=<…

2658a39

…try> Match on lang item kind instead of using an if/else chain r? `@ghost`

oli-obk marked this pull request as ready for review April 28, 2025 13:40

compiler-errors requested changes Apr 28, 2025

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compiler-errors self-assigned this Apr 28, 2025

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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 Apr 28, 2025

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Match on lang item kind instead of using an if/else chain #140386

Match on lang item kind instead of using an if/else chain #140386

oli-obk commented Apr 28, 2025 •

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rust-timer commented Apr 28, 2025

Match on lang item kind instead of using an if/else chain #140386

Are you sure you want to change the base?

Match on lang item kind instead of using an if/else chain #140386

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Overall result: ✅ improvements - no action needed

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rust-timer commented Apr 28, 2025

Overall result: ❌✅ regressions and improvements - please read the text below

oli-obk commented Apr 28, 2025 •

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