rustc_metadata: Encode the set of "rustdoc-reachable" def ids to metadata

[petrochenkov]

rustdoc currently calculates this set for every crate in the crate tree, so let's try to pre-compute it in advance.

[rustbot]

r? @jackh726

(rustbot has picked a reviewer for you, use r? to override)

[petrochenkov]

Initial version without any caching.
@bors try @rust-timer queue

[bors]

⌛ Trying commit d31d71e with merge 0f312812bb875cfde5e43719e27535fbd4580a30...

[bors]

☀️ Try build successful - checks-actions
Build commit: 0f312812bb875cfde5e43719e27535fbd4580a30 (0f312812bb875cfde5e43719e27535fbd4580a30)

[rust-timer]

Finished benchmarking commit (0f312812bb875cfde5e43719e27535fbd4580a30): comparison URL.

Overall result: ❌✅ regressions and improvements - 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.

Next Steps: If you can justify the regressions found in this try perf run, please indicate this with @rustbot label: +perf-regression-triaged along with sufficient written justification. If you cannot justify the regressions please fix the regressions and do another perf run. If the next run shows neutral or positive results, the label will be automatically removed.

@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)	0.8%	[0.5%, 1.4%]	17
Regressions ❌ (secondary)	1.0%	[0.4%, 1.9%]	10
Improvements ✅ (primary)	-1.3%	[-4.1%, -0.2%]	15
Improvements ✅ (secondary)	-2.6%	[-3.9%, -0.8%]	22
All ❌✅ (primary)	-0.2%	[-4.1%, 1.4%]	32

Max RSS (memory usage)

Results

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)	1.1%	[0.9%, 1.4%]	5
Regressions ❌ (secondary)	-	-	0
Improvements ✅ (primary)	-2.2%	[-3.2%, -1.3%]	4
Improvements ✅ (secondary)	-2.7%	[-3.8%, -2.0%]	4
All ❌✅ (primary)	-0.4%	[-3.2%, 1.4%]	9

Cycles

Results

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)	1.5%	[1.5%, 1.5%]	1
Regressions ❌ (secondary)	-	-	0
Improvements ✅ (primary)	-2.4%	[-3.2%, -1.8%]	4
Improvements ✅ (secondary)	-3.2%	[-3.9%, -2.0%]	14
All ❌✅ (primary)	-1.6%	[-3.2%, 1.5%]	5

[petrochenkov]

This is another tradeoff in favor of rustdoc at cost of rustc, and it makes less sense after #94857 is merged.