[experiment] Try to make index vec smaller when possible

[panstromek]

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This is very ugly and unsound, but I want to check CI and perf to see whether there's at least something to gain.

Notes

• this roundtrips every mutation through vec, which might mask any gains if it's not optimized out properly. I hope I'm gonna see at least some change to see whether it's worth cleaning up.

TODO

• not sure about Dyn[Send|Sync]
• Why I had to change the lifetimes in ProjectedMaybeOwner? (Failed in borrowck in rustc_middle)
• proper desc
• proper commits

[panstromek]

@bors try @rust-timer queue

[rust-bors]

☀️ Try build successful (CI)
Build commit: 76803df (76803df0625aa385701a24c186e4526355371fd5, parent: a1e52fc1cf67929a7c01ed9c037520e276ec98fd)

[rust-timer]

Finished benchmarking commit (76803df): 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)	0.4%	[0.2%, 0.7%]	155
Regressions ❌ (secondary)	0.4%	[0.1%, 1.0%]	107
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-0.5%	[-0.9%, -0.4%]	7
All ❌✅ (primary)	0.4%	[0.2%, 0.7%]	155

Max RSS (memory usage)

Results (primary -0.9%, secondary -1.2%)

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)	-0.9%	[-1.0%, -0.8%]	4
Improvements ✅ (secondary)	-1.2%	[-2.0%, -0.3%]	2
All ❌✅ (primary)	-0.9%	[-1.0%, -0.8%]	4

Cycles

Results (primary 2.2%)

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

	mean	range	count
Regressions ❌ (primary)	2.2%	[2.2%, 2.2%]	1
Regressions ❌ (secondary)	-	-	0
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	2.2%	[2.2%, 2.2%]	1

Binary size

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

Bootstrap: 519.113s -> 519.594s (0.09%)
Artifact size: 400.82 MiB -> 400.82 MiB (-0.00%)

[panstromek]

@bors try @rust-timer queue

[panstromek]

@bors try @rust-timer queue

[rust-bors]

☀️ Try build successful (CI)
Build commit: 979b836 (979b8369057e754d3efd9c1b6212527837effa46, parent: 5ff740e85e8569289a93573ad25f1295dfae0323)

[rust-timer]

Finished benchmarking commit (979b836): comparison URL.

Overall result: ❌ regressions - 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)	0.3%	[0.1%, 0.5%]	121
Regressions ❌ (secondary)	0.3%	[0.1%, 0.7%]	70
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	0.3%	[0.1%, 0.5%]	121

Max RSS (memory usage)

Results (primary -0.4%, 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)	2.3%	[0.9%, 3.6%]	2
Regressions ❌ (secondary)	0.8%	[0.8%, 0.8%]	1
Improvements ✅ (primary)	-1.3%	[-2.6%, -0.7%]	6
Improvements ✅ (secondary)	-1.4%	[-1.7%, -1.2%]	3
All ❌✅ (primary)	-0.4%	[-2.6%, 3.6%]	8

Cycles

Results (secondary 8.2%)

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)	18.7%	[18.7%, 18.7%]	1
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-2.4%	[-2.4%, -2.4%]	1
All ❌✅ (primary)	-	-	0

Binary size

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

Bootstrap: 518.77s -> 521.552s (0.54%)
Artifact size: 401.47 MiB -> 401.51 MiB (0.01%)

[panstromek]

@bors try @rust-timer queue

[rust-bors]

☀️ Try build successful (CI)
Build commit: 58d0082 (58d008275cf40c79fb3b7169e6ef0b09976d2af3, parent: b998449636a48e2c4a362809085b600a0174e1f2)

[rust-timer]

Finished benchmarking commit (58d0082): 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)	0.3%	[0.2%, 0.5%]	69
Regressions ❌ (secondary)	0.3%	[0.2%, 0.6%]	44
Improvements ✅ (primary)	-0.1%	[-0.4%, -0.1%]	5
Improvements ✅ (secondary)	-0.2%	[-0.3%, -0.1%]	19
All ❌✅ (primary)	0.3%	[-0.4%, 0.5%]	74

Max RSS (memory usage)

Results (primary -1.4%, 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)	-	-	0
Regressions ❌ (secondary)	-	-	0
Improvements ✅ (primary)	-1.4%	[-3.0%, -0.7%]	6
Improvements ✅ (secondary)	-2.4%	[-6.0%, -0.7%]	8
All ❌✅ (primary)	-1.4%	[-3.0%, -0.7%]	6

Cycles

Results (primary -0.1%, secondary 0.3%)

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

	mean	range	count
Regressions ❌ (primary)	3.6%	[3.6%, 3.6%]	1
Regressions ❌ (secondary)	4.0%	[2.1%, 7.0%]	9
Improvements ✅ (primary)	-1.9%	[-2.3%, -1.5%]	2
Improvements ✅ (secondary)	-3.1%	[-4.2%, -1.8%]	10
All ❌✅ (primary)	-0.1%	[-2.3%, 3.6%]	3

Binary size

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

Bootstrap: 524.623s -> 525.312s (0.13%)
Artifact size: 401.77 MiB -> 401.30 MiB (-0.12%)

[panstromek]

@bors try @rust-timer queue

[rust-bors]

☀️ Try build successful (CI)
Build commit: e21afdb (e21afdb99656464bd33cbca6b540e1b423f74697, parent: 89a99936d9e76a50e8df622e7242190841fd871b)

[rust-timer]

Finished benchmarking commit (e21afdb): 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)	0.3%	[0.2%, 0.4%]	75
Regressions ❌ (secondary)	0.3%	[0.0%, 0.6%]	36
Improvements ✅ (primary)	-0.1%	[-0.2%, -0.1%]	5
Improvements ✅ (secondary)	-0.3%	[-0.4%, -0.1%]	21
All ❌✅ (primary)	0.3%	[-0.2%, 0.4%]	80

Max RSS (memory usage)

Results (primary -1.2%, secondary -0.1%)

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)	7.1%	[7.1%, 7.1%]	1
Improvements ✅ (primary)	-1.2%	[-2.5%, -0.7%]	5
Improvements ✅ (secondary)	-1.5%	[-2.6%, -1.1%]	5
All ❌✅ (primary)	-1.2%	[-2.5%, -0.7%]	5

Cycles

Results (secondary 4.5%)

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)	5.0%	[2.0%, 12.0%]	12
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-1.5%	[-1.5%, -1.5%]	1
All ❌✅ (primary)	-	-	0

Binary size

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

Bootstrap: 522.035s -> 523.485s (0.28%)
Artifact size: 401.81 MiB -> 401.31 MiB (-0.12%)