Remove no-op cleanups as post-mono MIR opt

[Mark-Simulacrum]

On cargo this cuts ~5% of the LLVM IR lines we generate (measured with -Cno-prepopulate-passes). Opening to assess performance.

[Mark-Simulacrum]

@bors2 try @rust-timer queue

[rust-bors]

⌛ Trying commit e0423d5 with merge fb9de75…

To cancel the try build, run the command @bors2 try cancel.

[rust-bors]

☀️ Try build successful (CI)
Build commit: fb9de75 (fb9de75a813ea747c43682b22929463ada3f80de, parent: 5e749eb66f93ee998145399fbdde337e57cd72ef)

[rust-timer]

Finished benchmarking commit (fb9de75): 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)	18.6%	[0.2%, 60.9%]	6
Regressions ❌ (secondary)	9.4%	[0.4%, 18.4%]	2
Improvements ✅ (primary)	-1.9%	[-3.8%, -0.2%]	18
Improvements ✅ (secondary)	-2.5%	[-17.6%, -0.2%]	21
All ❌✅ (primary)	3.2%	[-3.8%, 60.9%]	24

Max RSS (memory usage)

Results (primary 8.9%, secondary 2.4%)

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

	mean	range	count
Regressions ❌ (primary)	9.2%	[1.3%, 33.3%]	34
Regressions ❌ (secondary)	3.6%	[2.9%, 4.9%]	4
Improvements ✅ (primary)	-1.6%	[-1.6%, -1.6%]	1
Improvements ✅ (secondary)	-2.4%	[-2.4%, -2.4%]	1
All ❌✅ (primary)	8.9%	[-1.6%, 33.3%]	35

Cycles

Results (primary 3.0%, secondary -3.6%)

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

	mean	range	count
Regressions ❌ (primary)	29.8%	[26.6%, 33.1%]	2
Regressions ❌ (secondary)	17.1%	[17.1%, 17.1%]	1
Improvements ✅ (primary)	-1.9%	[-3.0%, -1.2%]	11
Improvements ✅ (secondary)	-6.2%	[-20.2%, -2.1%]	8
All ❌✅ (primary)	3.0%	[-3.0%, 33.1%]	13

Binary size

Results (primary -0.7%, secondary -0.9%)

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)	0.0%	[0.0%, 0.0%]	1
Improvements ✅ (primary)	-0.7%	[-1.6%, -0.0%]	66
Improvements ✅ (secondary)	-0.9%	[-3.7%, -0.0%]	30
All ❌✅ (primary)	-0.7%	[-1.6%, -0.0%]	66

Bootstrap: 695.323s -> 698.39s (0.44%)
Artifact size: 371.80 MiB -> 371.90 MiB (0.03%)