Rollup of 2 pull requests

[Zalathar]

Successful merges:

• Revert "avoid phi node for pointers flowing into Vec appends #130998" #151150 (Revert "avoid phi node for pointers flowing into Vec appends avoid phi node for pointers flowing into Vec appends #130998")
• Reduce rustdoc GUI flakyness, take 2 #151145 (Reduce rustdoc GUI flakyness, take 2)

r? @ghost

Create a similar rollup

[Zalathar]

This is a special rollup to simultaneously fix two different sources of CI flakiness that have been blocking each other's fixes from landing.

@bors r+ rollup=never p=10

[rust-bors]

📌 Commit d87e654 has been approved by Zalathar

It is now in the queue for this repository.

[rust-bors]

☀️ Test successful - CI
Approved by: Zalathar
Pushing c9af9c1 to main...

[rust-timer]

📌 Perf builds for each rolled up PR:

PR#	Message	Perf Build Sha
#151145	Reduce rustdoc GUI flakyness, take 2	d75531b166230bfb4919f3313a031f17d5eef968 (link)
#151150	Revert "avoid phi node for pointers flowing into Vec append…	37a66606f9c025aceb5acde3ab93cd5496fb11cf (link)

previous master: b6fdaf2a15

In the case of a perf regression, run the following command for each PR you suspect might be the cause: @rust-timer build $SHA

[github-actions]

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 b6fdaf2 (parent) -> c9af9c1 (this PR)

Test differences

Show 197 test diffs

Stage 1

• [codegen] tests/codegen-llvm/lib-optimizations/append-elements.rs: ignore (ignored when the LLVM version 20.1.2 is older than 21.0.0) -> [missing] (J0)
• [codegen] tests/codegen-llvm/lib-optimizations/append-elements.rs: pass -> [missing] (J3)

Stage 2

• [codegen] tests/codegen-llvm/lib-optimizations/append-elements.rs: ignore (ignored when the LLVM version 20.1.8 is older than 21.0.0) -> [missing] (J1)
• [codegen] tests/codegen-llvm/lib-optimizations/append-elements.rs: ignore (ignored when the LLVM version 20.1.2 is older than 21.0.0) -> [missing] (J2)
• [codegen] tests/codegen-llvm/lib-optimizations/append-elements.rs: pass -> [missing] (J4)

Additionally, 192 doctest diffs were found. These are ignored, as they are noisy.

Job group index

• J0: x86_64-gnu-llvm-20-3
• J1: aarch64-gnu-llvm-20-1
• J2: x86_64-gnu-llvm-20-2
• J3: pr-check-2, x86_64-gnu-llvm-21-3
• J4: aarch64-apple, aarch64-gnu, aarch64-msvc-1, arm-android, armhf-gnu, dist-i586-gnu-i586-i686-musl, i686-gnu-1, i686-gnu-nopt-1, i686-msvc-1, test-various, x86_64-gnu, x86_64-gnu-llvm-21-2, x86_64-gnu-nopt, x86_64-gnu-stable, x86_64-mingw-1, x86_64-msvc-1

Test dashboard

Run

cargo run --manifest-path src/ci/citool/Cargo.toml -- \
    test-dashboard c9af9c1dc85a55e309345030ff9cb7ea247953fa --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

1. dist-aarch64-apple: 7951.3s -> 5853.6s (-26.4%)
2. dist-x86_64-apple: 8075.7s -> 5971.1s (-26.1%)
3. pr-check-1: 1997.5s -> 1477.1s (-26.1%)
4. dist-aarch64-msvc: 5370.2s -> 6306.3s (+17.4%)
5. x86_64-rust-for-linux: 3162.4s -> 2654.7s (-16.1%)
6. x86_64-gnu-gcc: 3440.2s -> 3014.6s (-12.4%)
7. x86_64-gnu-tools: 3742.0s -> 3356.7s (-10.3%)
8. dist-sparcv9-solaris: 5115.1s -> 5629.3s (+10.1%)
9. arm-android: 6419.8s -> 5780.5s (-10.0%)
10. aarch64-gnu-llvm-20-2: 3163.4s -> 2858.2s (-9.6%)

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]

Finished benchmarking commit (c9af9c1): comparison URL.

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

Our benchmarks found a performance regression caused by this PR.
This might be an actual regression, but it can also be just noise.

Next Steps:

• If the regression was expected or you think it can be justified,
  please write a comment with sufficient written justification, and add
  @rustbot label: +perf-regression-triaged to it, to mark the regression as triaged.
• If you think that you know of a way to resolve the regression, try to create
  a new PR with a fix for the regression.
• If you do not understand the regression or you think that it is just noise,
  you can ask the @rust-lang/wg-compiler-performance working group for help (members of this group
  were already notified of this PR).

@rustbot label: +perf-regression
cc @rust-lang/wg-compiler-performance

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)	1.4%	[0.6%, 2.8%]	3
Regressions ❌ (secondary)	1.4%	[0.3%, 4.5%]	6
Improvements ✅ (primary)	-0.7%	[-1.1%, -0.6%]	6
Improvements ✅ (secondary)	-0.2%	[-0.6%, -0.1%]	5
All ❌✅ (primary)	-0.0%	[-1.1%, 2.8%]	9

Max RSS (memory usage)

Results (primary -7.0%, secondary -2.1%)

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)	-7.0%	[-10.6%, -3.4%]	2
Improvements ✅ (secondary)	-2.1%	[-2.1%, -2.1%]	1
All ❌✅ (primary)	-7.0%	[-10.6%, -3.4%]	2

Cycles

Results (secondary 0.6%)

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)	3.4%	[3.4%, 3.4%]	1
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-2.3%	[-2.3%, -2.3%]	1
All ❌✅ (primary)	-	-	0

Binary size

Results (primary 0.1%, secondary 0.4%)

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

	mean	range	count
Regressions ❌ (primary)	0.5%	[0.0%, 1.5%]	6
Regressions ❌ (secondary)	0.8%	[0.1%, 1.5%]	2
Improvements ✅ (primary)	-0.1%	[-0.4%, -0.0%]	13
Improvements ✅ (secondary)	-0.1%	[-0.1%, -0.0%]	2
All ❌✅ (primary)	0.1%	[-0.4%, 1.5%]	19

Bootstrap: 475.873s -> 473.67s (-0.46%)
Artifact size: 383.65 MiB -> 383.57 MiB (-0.02%)

[Zalathar]

Perf changes appear to be the reverse of #130998 (comment), which is one of the PRs being reverted.