EffectiveVisibility: split fixed-point iteration into 2 stages

[Bryanskiy]

Use fixed-point iteration exclusively for modules and use chains during EffectiveVisibility computation. Other defs/fields are computed in a separate single pass.

r? @petrochenkov

[petrochenkov]

@bors try @rust-timer queue

[rust-bors]

☀️ Try build successful (CI)
Build commit: 0f6b3e5 (0f6b3e5650c214776ae5f15284bf9e746cdb46d1, parent: 783062d3c612d223e6841db4bbbc9bac4ab31ff4)

[rust-timer]

Finished benchmarking commit (0f6b3e5): comparison URL.

Overall result: ✅ improvements - no action needed

Benchmarking means the PR may be perf-sensitive. It's automatically marked not fit for rolling up. Overriding is possible but disadvised: it risks changing compiler perf.

@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
Regressions ❌ (secondary)	-	-	0
Improvements ✅ (primary)	-0.2%	[-0.3%, -0.2%]	4
Improvements ✅ (secondary)	-0.2%	[-0.2%, -0.2%]	2
All ❌✅ (primary)	-0.2%	[-0.3%, -0.2%]	4

Max RSS (memory usage)

Results (primary 1.7%, secondary 1.1%)

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

	mean	range	count
Regressions ❌ (primary)	1.7%	[1.7%, 1.7%]	1
Regressions ❌ (secondary)	1.1%	[0.5%, 2.4%]	4
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	1.7%	[1.7%, 1.7%]	1

Cycles

Results (primary 2.7%, secondary -1.6%)

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)	0.6%	[0.4%, 0.8%]	5
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-2.8%	[-4.1%, -0.5%]	10
All ❌✅ (primary)	2.7%	[2.7%, 2.7%]	1

Binary size

This perf run didn't have relevant results for this metric.

Bootstrap: 495.891s -> 494.917s (-0.20%)
Artifact size: 394.42 MiB -> 394.41 MiB (-0.00%)

[petrochenkov]

@bors try @rust-timer queue

[rust-bors]

☀️ Try build successful (CI)
Build commit: 7ee0eba (7ee0eba7a64e803714f46cbea6525bfdde6ad833, parent: 4feb7221f4d445120a5061b16ce7222adbfdf6f6)

[rust-timer]

Finished benchmarking commit (7ee0eba): comparison URL.

Overall result: ❌✅ regressions and improvements - please read:

Benchmarking means the PR may be perf-sensitive. It's automatically marked not fit for rolling up. Overriding is possible but disadvised: it risks changing compiler perf.

Next, please: If you can, justify the regressions found in this try perf run in writing along with @rustbot label: +perf-regression-triaged. If not, fix the regressions and do another perf run. Neutral or positive results will clear the label automatically.

@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
Regressions ❌ (secondary)	0.4%	[0.3%, 0.6%]	6
Improvements ✅ (primary)	-0.6%	[-0.9%, -0.2%]	20
Improvements ✅ (secondary)	-0.1%	[-0.3%, -0.1%]	10
All ❌✅ (primary)	-0.6%	[-0.9%, -0.2%]	20

Max RSS (memory usage)

Results (primary -2.1%, secondary 1.0%)

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)	4.4%	[2.9%, 6.1%]	6
Improvements ✅ (primary)	-2.1%	[-2.1%, -2.1%]	1
Improvements ✅ (secondary)	-2.4%	[-8.1%, -0.5%]	6
All ❌✅ (primary)	-2.1%	[-2.1%, -2.1%]	1

Cycles

Results (primary -2.1%, secondary -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)	1.3%	[0.7%, 2.1%]	4
Improvements ✅ (primary)	-2.1%	[-2.1%, -2.1%]	1
Improvements ✅ (secondary)	-1.7%	[-6.0%, -0.4%]	5
All ❌✅ (primary)	-2.1%	[-2.1%, -2.1%]	1

Binary size

This perf run didn't have relevant results for this metric.

Bootstrap: 495.518s -> 493.52s (-0.40%)
Artifact size: 394.42 MiB -> 394.41 MiB (-0.00%)

[petrochenkov]

Let's block on #156185 for now.
@rustbot blocked