rustdoc perf: clone clean::Item less

[lukas-code]

In #130798, I caused a small perf regression for rustdoc (see #130807 (comment)), so here is a small improvement to make up for it 😺.

This change is actually unrelated to the minor perf regression in Item::stability and instead fixes a more relevant perf problem that I found while investigating: For certain crates with many impls on type aliases, we unnecessarily cloned large clean::Items multiple times -- now we just borrow them.

[lukas-code]

@bors try @rust-timer queue

[bors]

⌛ Trying commit 345077a with merge 30e0b90...

[bors]

☀️ Try build successful - checks-actions
Build commit: 30e0b90 (30e0b903dddde0b3027145ac674a4d183cc0898f)

[rust-timer]

Finished benchmarking commit (30e0b90): comparison URL.

Overall result: ✅ improvements - no action needed

Benchmarking this pull request likely means that it is perf-sensitive, so we're automatically marking it as not fit for rolling up. While you can manually mark this PR as fit for rollup, we strongly recommend not doing so since this PR may lead to changes in compiler perf.

@bors rollup=never
@rustbot label: -S-waiting-on-perf -perf-regression

Instruction count

This is a highly reliable metric that was used to determine the overall result at the top of this comment.

	mean	range	count
Regressions ❌ (primary)	-	-	0
Regressions ❌ (secondary)	-	-	0
Improvements ✅ (primary)	-6.3%	[-15.5%, -0.2%]	3
Improvements ✅ (secondary)	-1.4%	[-1.4%, -1.4%]	1
All ❌✅ (primary)	-6.3%	[-15.5%, -0.2%]	3

Max RSS (memory usage)

Results (primary -28.3%)

This is a less reliable metric that may be of interest but was not used to determine the overall result at the top of this comment.

	mean	range	count
Regressions ❌ (primary)	2.5%	[2.5%, 2.5%]	1
Regressions ❌ (secondary)	-	-	0
Improvements ✅ (primary)	-38.6%	[-78.0%, -2.6%]	3
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	-28.3%	[-78.0%, 2.5%]	4

Cycles

Results (primary -15.9%, secondary 2.4%)

This is a less reliable metric that may be of interest but was not used to determine the overall result at the top of this comment.

	mean	range	count
Regressions ❌ (primary)	-	-	0
Regressions ❌ (secondary)	2.4%	[2.2%, 2.7%]	3
Improvements ✅ (primary)	-15.9%	[-15.9%, -15.9%]	1
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	-15.9%	[-15.9%, -15.9%]	1

Binary size

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

Bootstrap: 772.322s -> 772.862s (0.07%)
Artifact size: 340.90 MiB -> 340.91 MiB (0.00%)

[rustbot]

Some changes occurred in src/librustdoc/clean/types.rs

cc @camelid

[lukas-code]

r? @notriddle

[notriddle]

@bors r+ rollup=never

[bors]

📌 Commit 345077a has been approved by notriddle

It is now in the queue for this repository.

[bors]

⌛ Testing commit 345077a with merge 73a5576...

[bors]

💔 Test failed - checks-actions

[rust-log-analyzer]

A job failed! Check out the build log: (web) (plain)

Click to see the possible cause of the failure (guessed by this bot)

[notriddle]

500 error from Docket registry

@bors retry

[bors]

⌛ Testing commit 345077a with merge a3f76a2...

[bors]

☀️ Test successful - checks-actions
Approved by: notriddle
Pushing a3f76a2 to master...

[rust-timer]

Finished benchmarking commit (a3f76a2): comparison URL.

Overall result: ✅ improvements - no action needed

@rustbot label: -perf-regression

Instruction count

This is a highly reliable metric that was used to determine the overall result at the top of this comment.

	mean	range	count
Regressions ❌ (primary)	-	-	0
Regressions ❌ (secondary)	-	-	0
Improvements ✅ (primary)	-9.3%	[-15.5%, -3.1%]	2
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	-9.3%	[-15.5%, -3.1%]	2

Max RSS (memory usage)

Results (primary -28.3%, secondary 1.0%)

This is a less reliable metric that may be of interest but was not used to determine the overall result at the top of this comment.

	mean	range	count
Regressions ❌ (primary)	1.7%	[1.7%, 1.7%]	1
Regressions ❌ (secondary)	2.5%	[2.3%, 2.8%]	2
Improvements ✅ (primary)	-38.3%	[-78.5%, -1.2%]	3
Improvements ✅ (secondary)	-2.2%	[-2.2%, -2.2%]	1
All ❌✅ (primary)	-28.3%	[-78.5%, 1.7%]	4

Cycles

Results (primary -16.1%)

This is a less reliable metric that may be of interest but was not used to determine the overall result at the top of this comment.

	mean	range	count
Regressions ❌ (primary)	-	-	0
Regressions ❌ (secondary)	-	-	0
Improvements ✅ (primary)	-16.1%	[-16.1%, -16.1%]	1
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	-16.1%	[-16.1%, -16.1%]	1

Binary size

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

Bootstrap: 775.094s -> 776.908s (0.23%)
Artifact size: 341.33 MiB -> 341.40 MiB (0.02%)