[panstromek]

Just an idea - chain sometimes doesn't optimize as well and this iterator has encountered that issue before. Let's try using array of slices with flatten instead of Chain of slice and Option iterators

[panstromek]

@bors try @rust-timer queue

[rust-log-analyzer]

The job test-pr-check-2 failed! Check out the build log: (web) (plain enhanced) (plain)

Click to see the possible cause of the failure (guessed by this bot)

[rust-bors]

☀️ Try build successful (CI)
Build commit: 935dd45 (935dd45baa4c49545ad4f039eacbb0e7008a6aac)
Base parent: 8592206 (859220648edee0282af5b56f0b490cd4beb074db)

[rust-timer]

Finished benchmarking commit (935dd45): 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 rustc-perf
@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)	0.5%	[0.2%, 1.3%]	82
Regressions ❌ (secondary)	0.5%	[0.1%, 1.4%]	72
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-0.1%	[-0.1%, -0.1%]	1
All ❌✅ (primary)	0.5%	[0.2%, 1.3%]	82

Max RSS (memory usage)

Results (primary -0.4%, secondary -0.5%)

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

	mean	range	count
Regressions ❌ (primary)	0.5%	[0.4%, 0.7%]	5
Regressions ❌ (secondary)	1.4%	[1.4%, 1.4%]	1
Improvements ✅ (primary)	-0.8%	[-2.3%, -0.5%]	10
Improvements ✅ (secondary)	-1.5%	[-2.5%, -0.5%]	2
All ❌✅ (primary)	-0.4%	[-2.3%, 0.7%]	15

Cycles

Results (primary -0.0%, 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)	1.1%	[0.4%, 2.3%]	8
Regressions ❌ (secondary)	2.6%	[0.8%, 4.5%]	2
Improvements ✅ (primary)	-0.8%	[-1.7%, -0.5%]	11
Improvements ✅ (secondary)	-2.2%	[-2.2%, -2.2%]	1
All ❌✅ (primary)	-0.0%	[-1.7%, 2.3%]	19

Binary size

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

Bootstrap: 488.814s -> 487.859s (-0.20%)
Artifact size: 405.93 MiB -> 405.84 MiB (-0.02%)