[PERF] privacy: Visit DefIds once in DefIdVisitorSkeleton

[petrochenkov]

Testing various caching strategies in privacy visitors inspired by #146128.

[rustbot]

r? @lcnr

rustbot has assigned @lcnr.
They will have a look at your PR within the next two weeks and either review your PR or reassign to another reviewer.

Use r? to explicitly pick a reviewer

[petrochenkov]

@bors2 try @rust-timer queue

[rust-bors]

☀️ Try build successful (CI)
Build commit: 665fb0c (665fb0c6194a924362c4847361764e762a482668, parent: 910617d84d611e9ba508fd57a058c59b8a767697)

[rust-timer]

Finished benchmarking commit (665fb0c): comparison URL.

Overall result: ❌✅ regressions and improvements - 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)	0.4%	[0.1%, 1.0%]	141
Regressions ❌ (secondary)	0.4%	[0.1%, 1.0%]	77
Improvements ✅ (primary)	-1.3%	[-2.8%, -0.2%]	20
Improvements ✅ (secondary)	-1.2%	[-1.2%, -1.2%]	1
All ❌✅ (primary)	0.2%	[-2.8%, 1.0%]	161

Max RSS (memory usage)

Results (primary 0.9%)

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

	mean	range	count
Regressions ❌ (primary)	2.6%	[0.8%, 4.4%]	2
Regressions ❌ (secondary)	-	-	0
Improvements ✅ (primary)	-2.6%	[-2.6%, -2.6%]	1
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	0.9%	[-2.6%, 4.4%]	3

Cycles

Results (secondary -2.9%)

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)	-2.9%	[-2.9%, -2.9%]	1
All ❌✅ (primary)	-	-	0

Binary size

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

Bootstrap: 473.206s -> 472.658s (-0.12%)
Artifact size: 388.42 MiB -> 388.39 MiB (-0.01%)

[petrochenkov]

Interesting, per-DefId caching is a small regression in majority of cases, but provides larger speedups in some cases.
(From local testing, caching at DefId level doesn't help with #145741.)

I'll test per-Ty and per-TraitRef caching next.

[rustbot]

This PR was rebased onto a different master commit. Here's a range-diff highlighting what actually changed.

Rebasing is a normal part of keeping PRs up to date, so no action is needed—this note is just to help reviewers.

[petrochenkov]

@bors2 try @rust-timer queue

[petrochenkov]

The Ty-caching version helps with #145741, and reduces the compilation time from 35 to 16 seconds on my machine.

[rust-bors]

☀️ Try build successful (CI)
Build commit: f8e844a (f8e844a5ff3d4e587399f1873c352cd8bb5ba8fd, parent: acf243778e6c54cb7d54bee4be88e510e4be123e)

[rust-timer]

Finished benchmarking commit (f8e844a): comparison URL.

Overall result: ❌✅ regressions and improvements - 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)	0.6%	[0.1%, 1.5%]	148
Regressions ❌ (secondary)	0.8%	[0.1%, 3.1%]	130
Improvements ✅ (primary)	-0.5%	[-0.7%, -0.1%]	10
Improvements ✅ (secondary)	-0.5%	[-0.8%, -0.2%]	7
All ❌✅ (primary)	0.5%	[-0.7%, 1.5%]	158

Max RSS (memory usage)

Results (primary 1.4%)

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

	mean	range	count
Regressions ❌ (primary)	3.8%	[3.8%, 3.8%]	1
Regressions ❌ (secondary)	-	-	0
Improvements ✅ (primary)	-1.0%	[-1.0%, -1.0%]	1
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	1.4%	[-1.0%, 3.8%]	2

Cycles

Results (secondary 3.0%)

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)	3.0%	[2.0%, 4.9%]	9
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	-	-	0

Binary size

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

Bootstrap: 471.876s -> 472.593s (0.15%)
Artifact size: 388.40 MiB -> 388.36 MiB (-0.01%)