Small highlight.rs optimizations

[yotamofek]

Let's get a perf run to see if these actually make any difference?
r? @GuillaumeGomez

(third commit is a cleanup, first two are the optimizations)

[GuillaumeGomez]

@bors try @rust-timer queue

[yotamofek]

(for the record) cc #146992

[workingjubilee]

I wonder if we should have a rustdoc-specific perf check for cases where something only can affect rustdoc performance.

[yotamofek]

I wonder if we should have a rustdoc-specific perf check for cases where something only can affect rustdoc performance.

I've been fantasizing about that a lot. That would be sooo cool, at least for me personally (as someone whose majority of contributions tend to be around rustdoc perf and trying to improve it or at least not hurt it).

But to be fair, it does sound like something that would require too much investment from the already-swamped infra team, for something that wouldn't be THAT beneficial across the board. I mean, apart from rustdoc people, it might make the perf runner queue shorter, but it does seem to be pretty short lately (probably more so since the migration to the beefier runner)

[workingjubilee]

It doesn't sound that costly on the backend side of things, honestly. It probably just needs someone willing to implement it.

[rust-bors]

☀️ Try build successful (CI)
Build commit: ee53c6e (ee53c6ea7fb48a3718987f8c083341bb471de0db, parent: c0ee51f07d271f7cf3227c60a2c59aa18c959192)

[rust-timer]

Finished benchmarking commit (ee53c6e): comparison URL.

Overall result: ❌ regressions - 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)	0.3%	[0.1%, 2.9%]	16
Regressions ❌ (secondary)	0.2%	[0.1%, 0.3%]	8
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	0.3%	[0.1%, 2.9%]	16

Max RSS (memory usage)

Results (primary -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
Regressions ❌ (secondary)	-	-	0
Improvements ✅ (primary)	-0.4%	[-0.4%, -0.4%]	1
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	-0.4%	[-0.4%, -0.4%]	1

Cycles

Results (primary 2.7%, secondary -3.3%)

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

	mean	range	count
Regressions ❌ (primary)	2.7%	[2.7%, 2.7%]	1
Regressions ❌ (secondary)	-	-	0
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-3.3%	[-3.4%, -3.1%]	2
All ❌✅ (primary)	2.7%	[2.7%, 2.7%]	1

Binary size

Results (primary 1.1%)

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

	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: 471.818s -> 471.944s (0.03%)
Artifact size: 388.10 MiB -> 388.16 MiB (0.02%)