rustdoc: Optimize IdMap

[Kobzol]

Slightly optimizes IdMap, which is hot in markdown_links (context here). There are more improvements that can be made near this place, but this seemed like an easy win locally (although I tried it on top of #94857, so let's see what happens without that PR).

r? @petrochenkov

[Kobzol]

@bors try @rust-timer queue

[rust-timer]

Awaiting bors try build completion.

@rustbot label: +S-waiting-on-perf

[bors]

⌛ Trying commit 34e2d3b with merge 9342e57819dbf87e987f6c94aef9dd170cd69646...

[bors]

☀️ Try build successful - checks-actions
Build commit: 9342e57819dbf87e987f6c94aef9dd170cd69646 (9342e57819dbf87e987f6c94aef9dd170cd69646)

[rust-timer]

Queued 9342e57819dbf87e987f6c94aef9dd170cd69646 with parent 51ea9bb, future comparison URL.

[rust-timer]

Finished benchmarking commit (9342e57819dbf87e987f6c94aef9dd170cd69646): comparison url.

Summary:

• Primary benchmarks: 🎉 relevant improvements found
• Secondary benchmarks: 🎉 relevant improvements found

	Regressions 😿 (primary)	Regressions 😿 (secondary)	Improvements 🎉 (primary)	Improvements 🎉 (secondary)	All 😿 🎉 (primary)
count1	0	0	11	15	11
mean2	N/A	N/A	-0.7%	-0.6%	-0.7%
max	N/A	N/A	-3.1%	-2.3%	-3.1%

If you disagree with this performance assessment, please file an issue in rust-lang/rustc-perf.

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-review -S-waiting-on-perf -perf-regression

Footnotes

1. number of relevant changes↩

2. the arithmetic mean of the percent change↩

[Kobzol]

For comparison, when this was applied after the PR which stops resolver cloning, it improved helloworld doc by almost 5 %.

[petrochenkov]

Nice.
@bors r+

[bors]

📌 Commit 34e2d3b has been approved by petrochenkov

[bors]

⌛ Testing commit 34e2d3b with merge 5915368c701f5cf205894c7d1b0e7aa0a480d60a...

[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)

[Kobzol]

@bors retry

[bors]

⌛ Testing commit 34e2d3b with merge de1bc00...

[bors]

☀️ Test successful - checks-actions
Approved by: petrochenkov
Pushing de1bc00 to master...

[rust-timer]

Finished benchmarking commit (de1bc00): comparison url.

Summary:

• Primary benchmarks: 🎉 relevant improvements found
• Secondary benchmarks: 🎉 relevant improvements found

	Regressions 😿 (primary)	Regressions 😿 (secondary)	Improvements 🎉 (primary)	Improvements 🎉 (secondary)	All 😿 🎉 (primary)
count1	1	0	11	15	12
mean2	1.0%	N/A	-0.7%	-0.6%	-0.6%
max	1.0%	N/A	-3.1%	-2.3%	-3.1%

If you disagree with this performance assessment, please file an issue in rust-lang/rustc-perf.

@rustbot label: -perf-regression

Footnotes

1. number of relevant changes↩

2. the arithmetic mean of the percent change↩