Stop emitting UbChecks on every Vec→Slice

[scottmcm]

Spotted this in #148766's test changes. It doesn't seem like this ubcheck would catch anything useful; let's see if skipping it helps perf. (After all, this is inside every [] on a vec, among other things.)

[scottmcm]

@bors try @rust-timer queue

[rust-bors]

☀️ Try build successful (CI)
Build commit: d3405d7 (d3405d79c1b6f5617f04715f0b349c565c6a743d, parent: 000ccd651d6dfeab13f7703d92a5fd7a9ff7510f)

[rust-timer]

Finished benchmarking commit (d3405d7): 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)	1.6%	[0.6%, 2.4%]	4
Regressions ❌ (secondary)	0.4%	[0.0%, 2.3%]	7
Improvements ✅ (primary)	-1.4%	[-6.0%, -0.1%]	28
Improvements ✅ (secondary)	-0.7%	[-2.2%, -0.1%]	7
All ❌✅ (primary)	-1.0%	[-6.0%, 2.4%]	32

Max RSS (memory usage)

Results (primary 1.5%, secondary 1.9%)

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

	mean	range	count
Regressions ❌ (primary)	3.8%	[1.3%, 6.7%]	6
Regressions ❌ (secondary)	3.3%	[0.9%, 6.1%]	14
Improvements ✅ (primary)	-5.4%	[-7.2%, -3.5%]	2
Improvements ✅ (secondary)	-1.9%	[-2.6%, -1.5%]	5
All ❌✅ (primary)	1.5%	[-7.2%, 6.7%]	8

Cycles

Results (primary -1.0%, secondary -1.9%)

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

	mean	range	count
Regressions ❌ (primary)	2.6%	[2.3%, 2.8%]	2
Regressions ❌ (secondary)	2.3%	[2.1%, 2.8%]	3
Improvements ✅ (primary)	-2.4%	[-2.7%, -2.3%]	5
Improvements ✅ (secondary)	-4.0%	[-6.5%, -2.1%]	6
All ❌✅ (primary)	-1.0%	[-2.7%, 2.8%]	7

Binary size

Results (primary -0.2%, 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)	0.2%	[0.0%, 1.2%]	11
Regressions ❌ (secondary)	0.6%	[0.0%, 1.2%]	2
Improvements ✅ (primary)	-0.3%	[-0.9%, -0.0%]	64
Improvements ✅ (secondary)	-0.6%	[-3.6%, -0.0%]	20
All ❌✅ (primary)	-0.2%	[-0.9%, 1.2%]	75

Bootstrap: 481.34s -> 483.129s (0.37%)
Artifact size: 390.37 MiB -> 390.63 MiB (0.07%)

[rustbot]

r? @ibraheemdev

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[scottmcm]

Reconfirming after rebasing, but should be basically the same
@bors try @rust-timer queue

[scottmcm]

Annot: nothing actually overrode this anywhere, so removed it in favour of the usual PartialEq::ne.

[scottmcm]

annot: note that we're still inlining the whole &String → &str → &u8 part (since it'll essentially disappear in LLVM), just stopping at <[_]>::eq which sharing at the MIR level is probably best.

[rust-bors]

☀️ Try build successful (CI)
Build commit: fa07ba2 (fa07ba28fd0d71635c2fcc8ab0cb7944dd5fea85, parent: 04813e4de86a5e024e71756ef092637aa862c984)

[rust-timer]

Finished benchmarking commit (fa07ba2): 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)	1.4%	[0.3%, 2.6%]	5
Regressions ❌ (secondary)	0.6%	[0.0%, 2.5%]	5
Improvements ✅ (primary)	-1.5%	[-6.0%, -0.2%]	26
Improvements ✅ (secondary)	-0.6%	[-2.0%, -0.1%]	10
All ❌✅ (primary)	-1.0%	[-6.0%, 2.6%]	31

Max RSS (memory usage)

Results (primary -0.1%, 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)	4.3%	[2.1%, 5.4%]	3
Regressions ❌ (secondary)	3.5%	[0.8%, 5.8%]	9
Improvements ✅ (primary)	-4.6%	[-7.7%, -2.3%]	3
Improvements ✅ (secondary)	-1.7%	[-2.2%, -1.4%]	5
All ❌✅ (primary)	-0.1%	[-7.7%, 5.4%]	6

Cycles

Results (primary -1.0%, secondary -1.4%)

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)	2.5%	[2.2%, 2.9%]	3
Improvements ✅ (primary)	-2.6%	[-2.8%, -2.3%]	2
Improvements ✅ (secondary)	-3.3%	[-6.9%, -1.4%]	6
All ❌✅ (primary)	-1.0%	[-2.8%, 2.2%]	3

Binary size

Results (primary -0.2%, 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)	0.2%	[0.0%, 1.2%]	8
Regressions ❌ (secondary)	0.6%	[0.0%, 1.2%]	2
Improvements ✅ (primary)	-0.3%	[-0.9%, -0.0%]	57
Improvements ✅ (secondary)	-0.6%	[-3.7%, -0.0%]	20
All ❌✅ (primary)	-0.2%	[-0.9%, 1.2%]	65

Bootstrap: 481.395s -> 479.879s (-0.31%)
Artifact size: 390.31 MiB -> 390.61 MiB (0.08%)