Simplify the canonical enum clone branches to a copy statement by dianqk · Pull Request #148034 · rust-lang/rust

dianqk · 2025-10-23T15:13:29Z

I have overhauled MatchBranchSimplification in this PR. This pass tries to unify statements one by one, which is more readable and extensible.

This PR also unifies the following pattern that is mostly generated by GVN into one basic block that contains the copy statement:

match a {
    Foo::A(_) => *a,
    Foo::B => Foo::B
}

Fixes #128081.

dianqk · 2025-10-23T15:19:29Z

@bors try @rust-timer queue

[WIP] Simplify the canonical enum clone branches to a copy statement

rust-bors · 2025-10-23T15:43:28Z

💔 Test for b4269e3 failed: CI. Failed jobs:

try - dist-x86_64-linux (web logs, extended logs)

dianqk · 2025-10-23T23:51:23Z

@bors try @rust-timer queue

[WIP] Simplify the canonical enum clone branches to a copy statement

rust-bors · 2025-10-24T02:05:14Z

☀️ Try build successful (CI)
Build commit: 673e3f6 (673e3f61f8b218d304147e821d485edf0ebf3b09, parent: 6501e64fcb02d22b49d6e59d10a7692ec8095619)

rust-timer · 2025-10-24T03:16:55Z

Finished benchmarking commit (673e3f6): comparison URL.

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

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.

Next Steps: If you can justify the regressions found in this try perf run, please do so in sufficient writing along with @rustbot label: +perf-regression-triaged. If not, please fix the regressions and do another perf run. If its results are neutral or positive, the label will be automatically removed.

@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)	0.7%	[0.7%, 0.7%]	1
Regressions ❌ (secondary)	0.3%	[0.3%, 0.4%]	6
Improvements ✅ (primary)	-1.0%	[-2.4%, -0.1%]	6
Improvements ✅ (secondary)	-0.2%	[-1.3%, -0.1%]	17
All ❌✅ (primary)	-0.8%	[-2.4%, 0.7%]	7

Max RSS (memory usage)

Results (primary 2.8%)

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

	mean	range	count
Regressions ❌ (primary)	2.8%	[1.9%, 4.3%]	3
Regressions ❌ (secondary)	-	-	0
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	2.8%	[1.9%, 4.3%]	3

Cycles

Results (primary -3.4%, 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)	2.5%	[2.5%, 2.5%]	1
Improvements ✅ (primary)	-3.4%	[-3.4%, -3.4%]	1
Improvements ✅ (secondary)	-2.7%	[-4.5%, -2.1%]	6
All ❌✅ (primary)	-3.4%	[-3.4%, -3.4%]	1

Binary size

Results (primary -0.1%, secondary -0.1%)

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

	mean	range	count
Regressions ❌ (primary)	0.1%	[0.0%, 0.2%]	3
Regressions ❌ (secondary)	-	-	0
Improvements ✅ (primary)	-0.1%	[-0.4%, -0.0%]	20
Improvements ✅ (secondary)	-0.1%	[-0.1%, -0.0%]	41
All ❌✅ (primary)	-0.1%	[-0.4%, 0.2%]	23

Bootstrap: 476.496s -> 474.095s (-0.50%)
Artifact size: 390.49 MiB -> 390.42 MiB (-0.02%)

dianqk · 2025-10-26T06:53:24Z

@bors try @rust-timer queue

Simplify the canonical enum clone branches to a copy statement

rust-bors · 2025-10-26T09:05:46Z

☀️ Try build successful (CI)
Build commit: da8af3c (da8af3c91a895fd9646d0e6ef1477767ea0b6076, parent: e5177985a5493c783d6ba20960d2723d9d2e9214)

rust-bors · 2026-02-17T06:54:26Z

☀️ Try build successful (CI)
Build commit: 5f821fd (5f821fdf3e550566d4aa962998f26d502fb3b896, parent: 3c9faa0d037b9eecda4a440cc482ff7f960fb8a5)

rust-timer · 2026-02-17T07:40:14Z

Finished benchmarking commit (5f821fd): comparison URL.

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

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.

Next Steps: If you can justify the regressions found in this try perf run, please do so in sufficient writing along with @rustbot label: +perf-regression-triaged. If not, please fix the regressions and do another perf run. If its results are neutral or positive, the label will be automatically removed.

@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)	0.7%	[0.7%, 0.7%]	1
Regressions ❌ (secondary)	0.3%	[0.3%, 0.3%]	2
Improvements ✅ (primary)	-1.1%	[-2.0%, -0.7%]	4
Improvements ✅ (secondary)	-0.3%	[-0.3%, -0.2%]	6
All ❌✅ (primary)	-0.8%	[-2.0%, 0.7%]	5

Max RSS (memory usage)

Results (primary -3.6%, secondary 5.5%)

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)	5.5%	[5.5%, 5.5%]	1
Improvements ✅ (primary)	-3.6%	[-4.5%, -2.4%]	4
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	-3.6%	[-4.5%, -2.4%]	4

Cycles

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

Binary size

Results (primary -0.1%, secondary -0.0%)

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

	mean	range	count
Regressions ❌ (primary)	0.1%	[0.0%, 0.2%]	5
Regressions ❌ (secondary)	0.0%	[0.0%, 0.0%]	1
Improvements ✅ (primary)	-0.2%	[-0.8%, -0.0%]	9
Improvements ✅ (secondary)	-0.0%	[-0.0%, -0.0%]	2
All ❌✅ (primary)	-0.1%	[-0.8%, 0.2%]	14

Bootstrap: 480.798s -> 481.457s (0.14%)
Artifact size: 395.81 MiB -> 397.87 MiB (0.52%)

dianqk · 2026-02-17T12:44:05Z

From the several results, it appears regex-automata-0.4.8 is flaky.

@rustbot review

cjgillot · 2026-02-17T13:49:14Z

@bors r+

rust-bors · 2026-02-17T13:49:17Z

📌 Commit b4e3de0 has been approved by cjgillot

It is now in the queue for this repository.

JonathanBrouwer · 2026-02-18T21:06:46Z

@bors p=2
Scheduling

Simplify the canonical enum clone branches to a copy statement I have overhauled MatchBranchSimplification in this PR. This pass tries to unify statements one by one, which is more readable and extensible. This PR also unifies the following pattern that is mostly generated by GVN into one basic block that contains the copy statement: ```rust match a { Foo::A(_) => *a, Foo::B => Foo::B } ``` Fixes #128081.

JonathanBrouwer · 2026-02-19T04:18:11Z

@bors yield
Yielding to the rollup that spuriously failed

rust-bors · 2026-02-19T04:18:14Z

Auto build cancelled. Cancelled workflows:

https://github.com/rust-lang/rust/actions/runs/22168202420

The next pull request likely to be tested is #152825.

rust-bors · 2026-02-19T13:09:30Z

☀️ Test successful - CI
Approved by: cjgillot
Duration: 3h 12m 54s
Pushing 41198cb to main...

github-actions · 2026-02-19T13:12:24Z

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 fbd6934 (parent) -> 41198cb (this PR)

Test differences

Show 30 test diffs

Stage 1

[mir-opt] tests/mir-opt/pre-codegen/copy_and_clone.rs#CLONE: [missing] -> pass (J1)
[mir-opt] tests/mir-opt/pre-codegen/copy_and_clone.rs#COPY: [missing] -> pass (J1)

Stage 2

[mir-opt] tests/mir-opt/pre-codegen/copy_and_clone.rs#CLONE: [missing] -> pass (J0)
[mir-opt] tests/mir-opt/pre-codegen/copy_and_clone.rs#COPY: [missing] -> pass (J0)

Additionally, 26 doctest diffs were found. These are ignored, as they are noisy.

Job group index

Test dashboard

Run

cargo run --manifest-path src/ci/citool/Cargo.toml -- \
    test-dashboard 41198cb9659f3cc7c4a1a3ee97bc4af78bee403e --output-dir test-dashboard

And then open test-dashboard/index.html in your browser to see an overview of all executed tests.

Job duration changes

aarch64-apple: 5h 28m -> 2h 34m (-52.9%)
dist-x86_64-apple: 2h 5m -> 2h 38m (+27.0%)
tidy: 2m 23s -> 2m 49s (+18.3%)
dist-aarch64-apple: 2h 38m -> 2h 12m (-16.3%)
dist-aarch64-llvm-mingw: 1h 32m -> 1h 46m (+15.1%)
i686-gnu-nopt-1: 1h 59m -> 2h 9m (+8.7%)
x86_64-gnu-miri: 1h 11m -> 1h 16m (+8.2%)
x86_64-gnu-llvm-20: 1h 11m -> 1h 15m (+6.8%)
dist-powerpc-linux: 1h 33m -> 1h 27m (-6.6%)
dist-loongarch64-musl: 1h 45m -> 1h 51m (+5.8%)

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 · 2026-02-19T13:51:05Z

Finished benchmarking commit (41198cb): comparison URL.

Overall result: ✅ improvements - no action needed

@rustbot label: -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)	0.7%	[0.7%, 0.7%]	1
Regressions ❌ (secondary)	0.2%	[0.2%, 0.2%]	1
Improvements ✅ (primary)	-0.6%	[-2.1%, -0.2%]	9
Improvements ✅ (secondary)	-0.5%	[-0.8%, -0.2%]	14
All ❌✅ (primary)	-0.5%	[-2.1%, 0.7%]	10

Max RSS (memory usage)

Results (primary -0.7%)

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

	mean	range	count
Regressions ❌ (primary)	2.9%	[2.5%, 3.3%]	2
Regressions ❌ (secondary)	-	-	0
Improvements ✅ (primary)	-4.3%	[-4.5%, -4.0%]	2
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	-0.7%	[-4.5%, 3.3%]	4

Cycles

Results (primary -2.2%, secondary 9.6%)

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)	9.6%	[9.6%, 9.6%]	1
Improvements ✅ (primary)	-2.2%	[-2.2%, -2.2%]	1
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	-2.2%	[-2.2%, -2.2%]	1

Binary size

Results (primary -0.1%, secondary -0.0%)

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

	mean	range	count
Regressions ❌ (primary)	0.1%	[0.0%, 0.2%]	5
Regressions ❌ (secondary)	0.0%	[0.0%, 0.0%]	1
Improvements ✅ (primary)	-0.2%	[-0.8%, -0.0%]	9
Improvements ✅ (secondary)	-0.0%	[-0.0%, -0.0%]	2
All ❌✅ (primary)	-0.1%	[-0.8%, 0.2%]	14

Bootstrap: 481.318s -> 479.676s (-0.34%)
Artifact size: 397.87 MiB -> 397.83 MiB (-0.01%)

…on-flag-check, r=clubby789,jieyouxu Improve runtest revision redundant cfg check While attempting to ingest rust-lang#148034 via ferrocene/ferrocene#2172 we noticed a test failure, as we add some `compile_flags` to tests. We saw a failure looking like this: ``` Testing stage1 with compiletest suite=mir-opt mode=mir-opt (x86_64-unknown-linux-gnu) running 2 tests 2026-02-20T20:21:28.846102Z ERROR compiletest::runtest: redundant cfg argument `copy` is already created by the revision [mir-opt] tests/mir-opt/pre-codegen/copy_and_clone.rs#COPY ... F . ``` While my Rust checkout passed: ``` Testing stage1 with compiletest suite=mir-opt mode=mir-opt (x86_64-unknown-linux-gnu) running 2 tests .. test result: ok. 2 passed; 0 failed; 0 ignored; 0 measured; 381 filtered out; finished in 107.10ms ``` This caused me to add some debugging statements. Ferrocene: ``` 2026-02-20T21:05:39.808427Z ERROR compiletest::runtest: "copy": does ["--edition=2015", "--cfg=copy"] contain `"--cfg=copy"` or `["--cfg", "copy"]`? true 2026-02-20T21:05:39.808427Z ERROR compiletest::runtest: "clone": does ["--edition=2015"] contain `"--cfg=clone"` or `["--cfg", "clone"]`? false 2026-02-20T21:05:39.808435Z ERROR compiletest::runtest: redundant cfg argument `copy` is already created by the revision ``` Rust: ``` 2026-02-20T21:04:18.493158Z ERROR compiletest::runtest: "copy": does ["--cfg=copy"] contain `"--cfg=copy"` or `["--cfg", "copy"]`? false 2026-02-20T21:04:18.493158Z ERROR compiletest::runtest: "clone": does [] contain `"--cfg=clone"` or `["--cfg", "clone"]`? false ``` I noticed while reviewing the related functionality that there is a call to `.windows(2)` in the relevant check for redundant cfgs: https://github.com/rust-lang/rust/blob/0376d43d443cba463a0b6a6ec9140ea17d7b7130/src/tools/compiletest/src/runtest.rs#L507-L511 Noting: https://github.com/rust-lang/rust/blob/0376d43d443cba463a0b6a6ec9140ea17d7b7130/library/core/src/slice/mod.rs#L1064-L1066 Because of this, the revision check was getting an empty iterator when `self.props.compile_flags` was length 0 or 1. This fix adjusts the check to handle such cases. I went ahead and fixed the relevant test (4b3cd9b) that was impacted by this. I do not suspect there are others, at least within the scope that Ferrocene tests, as we have not previously seen this failure.

rustbot added S-waiting-on-author Status: This is awaiting some action (such as code changes or more information) from the author. T-compiler Relevant to the compiler team, which will review and decide on the PR/issue. labels Oct 23, 2025

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rustbot added the S-waiting-on-perf Status: Waiting on a perf run to be completed. label Oct 23, 2025

rust-bors bot added a commit that referenced this pull request Oct 23, 2025

Auto merge of #148034 - dianqk:matchbr-copy, r=<try>

b4269e3

[WIP] Simplify the canonical enum clone branches to a copy statement

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dianqk force-pushed the matchbr-copy branch from 8843d6b to b9944dd Compare October 23, 2025 22:17

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Auto merge of #148034 - dianqk:matchbr-copy, r=<try>

673e3f6

[WIP] Simplify the canonical enum clone branches to a copy statement

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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 Oct 24, 2025

dianqk force-pushed the matchbr-copy branch 2 times, most recently from d2deaa3 to 8a2e9e4 Compare October 26, 2025 05:22

dianqk changed the title ~~[WIP] Simplify the canonical enum clone branches to a copy statement~~ Simplify the canonical enum clone branches to a copy statement Oct 26, 2025

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rust-bors bot added a commit that referenced this pull request Oct 26, 2025

Auto merge of #148034 - dianqk:matchbr-copy, r=<try>

da8af3c

Simplify the canonical enum clone branches to a copy statement

rustbot added the S-waiting-on-perf Status: Waiting on a perf run to be completed. label Oct 26, 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 Feb 17, 2026

rustbot added S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. and removed S-waiting-on-author Status: This is awaiting some action (such as code changes or more information) from the author. labels Feb 17, 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 Feb 17, 2026

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rust-bors bot added merged-by-bors This PR was explicitly merged by bors. and removed S-waiting-on-bors Status: Waiting on bors to run and complete tests. Bors will change the label on completion. labels Feb 19, 2026

rust-bors bot merged commit 41198cb into rust-lang:main Feb 19, 2026
13 checks passed

rustbot added this to the 1.95.0 milestone Feb 19, 2026

dianqk deleted the matchbr-copy branch February 19, 2026 13:10

rustbot removed the perf-regression Performance regression. label Feb 19, 2026

Hoverbear mentioned this pull request Feb 20, 2026

Improve runtest revision redundant cfg check #152925

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

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

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Test differences

Stage 1

Stage 2

Job duration changes

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Overall result: ✅ improvements - no action needed

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