Rollup of 4 pull requests by JonathanBrouwer · Pull Request #154300 · rust-lang/rust

JonathanBrouwer · 2026-03-24T09:54:05Z

Successful merges:

Use a safe BucketIndex abstraction in VecCache #153434 (Use a safe BucketIndex abstraction in VecCache)
Defer codegen for the VaList Drop impl to actual uses #154133 (Defer codegen for the VaList Drop impl to actual uses)
fix/extend some mir-opt comments #154297 (fix/extend some mir-opt comments)
document some functions on AttributeExt #154299 (document some functions on AttributeExt)

This allows compiling libcore with codegen backends that don't actually implement VaList like cg_clif.

The current code for indexing into bucket arrays is quite tricky and unsafe, partly because it has to keep manually assuring the compiler that a bucket index is always less than 21. By encapsulating that knowledge in a 21-value enum, we can make the code clearer and safer, without giving up performance. Having a dedicated `BucketIndex` type could also help with further cleanups of `VecCache` indexing.

Use a safe `BucketIndex` abstraction in `VecCache` The current code for indexing into bucket arrays is quite tricky and unsafe, partly because it has to keep manually assuring the compiler that a bucket index is always less than 21. By encapsulating that knowledge in a 21-value enum, we can make the code clearer and safer, without giving up performance. Having a dedicated `BucketIndex` type could also help with further cleanups of `VecCache` indexing.

… r=nnethercote Defer codegen for the VaList Drop impl to actual uses This allows compiling libcore with codegen backends that don't actually implement VaList like cg_clif.

@cjgillot

fix/extend some mir-opt comments Looks like CopyProp was refactored without updating that comment. And for GVN, I think this is what you had in mind @cjgillot but would be great if you could have a look.

@jyn514

…t, r=JonathanBrouwer document some functions on AttributeExt r? @jyn514

JonathanBrouwer · 2026-03-24T09:54:26Z

@bors r+ rollup=never p=5

rust-bors · 2026-03-24T09:54:29Z

📌 Commit 6f67067 has been approved by JonathanBrouwer

It is now in the queue for this repository.

rust-bors · 2026-03-24T14:28:58Z

☀️ Test successful - CI
Approved by: JonathanBrouwer
Duration: 3h 13m 44s
Pushing 0312931 to main...

github-actions · 2026-03-24T14:32:11Z

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 cde9cf0 (parent) -> 0312931 (this PR)

Test differences

Show 40 test diffs

Stage 0

vec_cache::tests::bucket_index_capacity: [missing] -> pass (J1)
vec_cache::tests::bucket_index_iter_all_len: [missing] -> pass (J1)
vec_cache::tests::bucket_index_n_buckets: [missing] -> pass (J1)
vec_cache::tests::bucket_index_round_trip: [missing] -> pass (J1)
vec_cache::tests::vec_cache_empty: pass -> [missing] (J1)
vec_cache::tests::vec_cache_empty_exhaustive: [missing] -> pass (J1)

Stage 1

vec_cache::tests::bucket_index_capacity: [missing] -> pass (J0)
vec_cache::tests::bucket_index_iter_all_len: [missing] -> pass (J0)
vec_cache::tests::bucket_index_n_buckets: [missing] -> pass (J0)
vec_cache::tests::bucket_index_round_trip: [missing] -> pass (J0)
vec_cache::tests::vec_cache_empty: pass -> [missing] (J0)
vec_cache::tests::vec_cache_empty_exhaustive: [missing] -> pass (J0)

Additionally, 28 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 0312931d8c0ba1a28268a12c06202b68cbc65f76 --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

optional-x86_64-gnu-parallel-frontend: 2h 8m -> 2h 41m (+26.3%)
dist-apple-various: 1h 40m -> 2h 2m (+22.0%)
x86_64-gnu-debug: 1h 48m -> 2h 11m (+21.2%)
x86_64-rust-for-linux: 43m 54s -> 52m 10s (+18.8%)
x86_64-gnu-llvm-22-2: 1h 24m -> 1h 40m (+18.7%)
pr-check-1: 28m 9s -> 33m 9s (+17.8%)
dist-aarch64-llvm-mingw: 1h 40m -> 1h 57m (+17.7%)
dist-x86_64-apple: 1h 50m -> 2h 8m (+17.0%)
x86_64-mingw-2: 2h 36m -> 2h 57m (+13.3%)
i686-gnu-2: 1h 31m -> 1h 43m (+13.3%)

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 · 2026-03-24T15:08:43Z

Finished benchmarking commit (0312931): comparison URL.

Overall result: no relevant changes - no action needed

@rustbot label: -perf-regression

Instruction count

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

Max RSS (memory usage)

Results (primary 3.1%, secondary 1.1%)

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

	mean	range	count
Regressions ❌ (primary)	3.1%	[2.7%, 3.5%]	4
Regressions ❌ (secondary)	2.9%	[2.2%, 3.6%]	4
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-2.4%	[-3.1%, -1.7%]	2
All ❌✅ (primary)	3.1%	[2.7%, 3.5%]	4

Cycles

Results (secondary -0.7%)

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)	-3.8%	[-3.8%, -3.8%]	1
All ❌✅ (primary)	-	-	0

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
Regressions ❌ (secondary)	-	-	0
Improvements ✅ (primary)	-0.1%	[-0.1%, -0.0%]	54
Improvements ✅ (secondary)	-0.1%	[-0.1%, -0.0%]	22
All ❌✅ (primary)	-0.1%	[-0.1%, -0.0%]	54

Bootstrap: 486.46s -> 484.31s (-0.44%)
Artifact size: 394.96 MiB -> 394.79 MiB (-0.04%)

bjorn3 and others added 10 commits March 20, 2026 11:48

Defer codegen for the VaList Drop impl to actual uses

0b69ff5

This allows compiling libcore with codegen backends that don't actually implement VaList like cg_clif.

CopyProp: fix outdated comment

bd16cd4

GVN: add clarifying example to reference comment

fb2b003

document some functions on AttributeExt

c87cd68

Add comments

366cf88

Rollup merge of rust-lang#154133 - bjorn3:va_list_drop_defer_codegen,…

fad2a35

… r=nnethercote Defer codegen for the VaList Drop impl to actual uses This allows compiling libcore with codegen backends that don't actually implement VaList like cg_clif.

Rollup merge of rust-lang#154297 - RalfJung:mir-opt-comments, r=dianqk

a5a286d

fix/extend some mir-opt comments Looks like CopyProp was refactored without updating that comment. And for GVN, I think this is what you had in mind @cjgillot but would be great if you could have a look.

Rollup merge of rust-lang#154299 - jdonszelmann:document-attribute-ex…

6f67067

…t, r=JonathanBrouwer document some functions on AttributeExt r? @jyn514

rust-bors bot added the rollup A PR which is a rollup label Mar 24, 2026

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. T-libs Relevant to the library team, which will review and decide on the PR/issue. labels Mar 24, 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 Mar 24, 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 Mar 24, 2026

rust-bors bot merged commit 0312931 into rust-lang:main Mar 24, 2026
12 checks passed

rustbot added this to the 1.96.0 milestone Mar 24, 2026

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Rollup of 4 pull requests#154300

Rollup of 4 pull requests#154300
rust-bors[bot] merged 10 commits intorust-lang:mainfrom
JonathanBrouwer:rollup-MkFxTPv

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Test differences

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Stage 1

Job duration changes

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rust-timer commented Mar 24, 2026

Overall result: no relevant changes - no action needed

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