Remove useless assumes from slice::iter(_mut)

[scottmcm]

You were right in #111395 (comment),
r? @the8472

LLVM already removes these assumes while optimizing, as can be seen in https://rust.godbolt.org/z/KTfWKbdEM.

[thomcc]

Looks great, r=me after green CI (sorry for stealing it, linked to me in Discord and I'm already here). I don't think a perf run is needed but lets not roll it up just in case.

@bors rollup=never
r? @thomcc

[thomcc]

Oh wait, it's rollup=never so there's no reason not to r+ it now.

@bors r+

[bors]

📌 Commit 4cde41a80030c9ecf354e113756c6a816e4ad085 has been approved by thomcc

It is now in the queue for this repository.

[bors]

🌲 The tree is currently closed for pull requests below priority 50. This pull request will be tested once the tree is reopened.

[bors]

⌛ Testing commit 4cde41a80030c9ecf354e113756c6a816e4ad085 with merge 9310adfaa815d4c86044af0e176e7c83788990e7...

[bors]

💔 Test failed - checks-actions

[scottmcm]

@bors retry

[scottmcm]

Rebased atop #111395.

@bors r=thomcc

[bors]

📌 Commit e5e7eb764def1d3fd92eefd0ec63eda4970f8631 has been approved by thomcc

It is now in the queue for this repository.

[bors]

⌛ Testing commit e5e7eb764def1d3fd92eefd0ec63eda4970f8631 with merge ae19200d5e51f1c0a62d525d1adf56b63d5bc0ec...

[bors]

💔 Test failed - checks-actions

[scottmcm]

Oh, interesting, this with something else that went in after I last rebased means that slice::Iter::new is now small enough that it gets mir-inlined. Rebased again and reblessed.

@bors r=thomcc

[bors]

📌 Commit c50a2e1 has been approved by thomcc

It is now in the queue for this repository.

[bors]

⌛ Testing commit c50a2e1 with merge 16d3e18...

[bors]

☀️ Test successful - checks-actions
Approved by: thomcc
Pushing 16d3e18 to master...

[rust-timer]

Finished benchmarking commit (16d3e18): comparison URL.

Overall result: ❌✅ regressions and improvements - ACTION NEEDED

Next Steps: If you can justify the regressions found in this perf run, please indicate this with @rustbot label: +perf-regression-triaged along with sufficient written justification. If you cannot justify the regressions please open an issue or create a new PR that fixes the regressions, add a comment linking to the newly created issue or PR, and then add the perf-regression-triaged label to this PR.

@rustbot label: +perf-regression
cc @rust-lang/wg-compiler-performance

Instruction count

This is a highly reliable metric that was used to determine the overall result at the top of this comment.

	mean	range	count
Regressions ❌ (primary)	-	-	0
Regressions ❌ (secondary)	1.1%	[1.1%, 1.1%]	2
Improvements ✅ (primary)	-0.8%	[-1.7%, -0.3%]	85
Improvements ✅ (secondary)	-0.7%	[-1.4%, -0.4%]	46
All ❌✅ (primary)	-0.8%	[-1.7%, -0.3%]	85

Max RSS (memory usage)

Results

This is a less reliable metric that may be of interest but was not used to determine the overall result at the top of this comment.

	mean	range	count
Regressions ❌ (primary)	2.8%	[2.7%, 2.9%]	2
Regressions ❌ (secondary)	-	-	0
Improvements ✅ (primary)	-3.6%	[-5.1%, -2.3%]	4
Improvements ✅ (secondary)	-3.1%	[-3.3%, -2.9%]	2
All ❌✅ (primary)	-1.5%	[-5.1%, 2.9%]	6

Cycles

Results

This is a less reliable metric that may be of interest but was not used to determine the overall result at the top of this comment.

	mean	range	count
Regressions ❌ (primary)	-	-	0
Regressions ❌ (secondary)	-	-	0
Improvements ✅ (primary)	-1.3%	[-1.9%, -0.8%]	3
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	-1.3%	[-1.9%, -0.8%]	3

Binary size

Results

This is a less reliable metric that may be of interest but was not used to determine the overall result at the top of this comment.

	mean	range	count
Regressions ❌ (primary)	0.4%	[0.0%, 5.7%]	56
Regressions ❌ (secondary)	-	-	0
Improvements ✅ (primary)	-0.2%	[-1.4%, -0.0%]	11
Improvements ✅ (secondary)	-0.1%	[-0.1%, -0.1%]	4
All ❌✅ (primary)	0.3%	[-1.4%, 5.7%]	67

Bootstrap: 659.629s -> 659.427s (-0.03%)

[nnethercote]

Perf improvements here massively outweigh the small number of regressions.

@rustbot label: +perf-regression-triaged