[rustdoc] a small performance improvement: only allocate new string if there are DOS backlines in highlight.rs

[krtab]

r? @GuillaumeGomez

[GuillaumeGomez]

Let's see how it impacts it. :)

@bors2 try @rust-timer queue

[rust-bors]

☀️ Try build successful (CI)
Build commit: b1991c3 (b1991c3da006335cf156110d9ca7f6dcd0abf4f3, parent: 4a54b26d30dac43778afb0e503524b763fce0eee)

[rust-timer]

Finished benchmarking commit (b1991c3): comparison URL.

Overall result: ✅ 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
Improvements ✅ (primary)	-0.2%	[-0.3%, -0.2%]	3
Improvements ✅ (secondary)	-0.4%	[-0.6%, -0.0%]	8
All ❌✅ (primary)	-0.2%	[-0.3%, -0.2%]	3

Max RSS (memory usage)

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

Cycles

Results (secondary -2.7%)

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)	-	-	0
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-2.7%	[-2.9%, -2.6%]	2
All ❌✅ (primary)	-	-	0

Binary size

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

Bootstrap: 473.216s -> 472.246s (-0.20%)
Artifact size: 388.39 MiB -> 388.36 MiB (-0.01%)

[GuillaumeGomez]

Up to -0.5%, well done!

@bors r+

[bors]

📌 Commit e98856b has been approved by GuillaumeGomez

It is now in the queue for this repository.

[bors]

⌛ Testing commit e98856b with merge 910617d...

[bors]

☀️ Test successful - checks-actions
Approved by: GuillaumeGomez
Pushing 910617d to master...

[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 82224f6 (parent) -> 910617d (this PR)

Test differences

Show 4 test diffs

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

Test dashboard

Run

cargo run --manifest-path src/ci/citool/Cargo.toml -- \
    test-dashboard 910617d84d611e9ba508fd57a058c59b8a767697 --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-android: 1510.8s -> 1127.6s (-25.4%)
2. pr-check-1: 1680.4s -> 1435.3s (-14.6%)
3. aarch64-apple: 8661.2s -> 9901.1s (14.3%)
4. dist-ohos-aarch64: 4322.8s -> 4925.3s (13.9%)
5. dist-aarch64-msvc: 6325.5s -> 5475.7s (-13.4%)
6. x86_64-rust-for-linux: 2967.7s -> 2603.5s (-12.3%)
7. i686-gnu-1: 8270.7s -> 7314.9s (-11.6%)
8. aarch64-gnu-debug: 4118.6s -> 3657.7s (-11.2%)
9. x86_64-gnu-llvm-20-2: 6187.8s -> 5553.0s (-10.3%)
10. i686-gnu-2: 6162.3s -> 5547.0s (-10.0%)

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 (910617d): 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
Regressions ❌ (secondary)	-	-	0
Improvements ✅ (primary)	-0.2%	[-0.3%, -0.1%]	4
Improvements ✅ (secondary)	-0.2%	[-0.5%, -0.0%]	5
All ❌✅ (primary)	-0.2%	[-0.3%, -0.1%]	4

Max RSS (memory usage)

Results (primary 2.3%, secondary -2.6%)

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

	mean	range	count
Regressions ❌ (primary)	2.3%	[2.3%, 2.3%]	1
Regressions ❌ (secondary)	-	-	0
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-2.6%	[-2.6%, -2.6%]	1
All ❌✅ (primary)	2.3%	[2.3%, 2.3%]	1

Cycles

Results (primary -3.2%, secondary 0.8%)

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)	3.2%	[2.7%, 4.2%]	3
Improvements ✅ (primary)	-3.2%	[-3.2%, -3.2%]	1
Improvements ✅ (secondary)	-2.7%	[-2.7%, -2.7%]	2
All ❌✅ (primary)	-3.2%	[-3.2%, -3.2%]	1

Binary size

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

Bootstrap: 473.927s -> 473.206s (-0.15%)
Artifact size: 388.42 MiB -> 388.42 MiB (0.00%)