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Simplify Vec using iter::repeat_n - #104596

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Simplify Vec using iter::repeat_n#104596
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@scottmcmscottmcm commented Nov 19, 2022•
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By using repeat_n instead of ExtendElement, we can delete a bunch more unsafe code from Vec.

All the codegen tests are passing (and I made one stricter to help be sure), so let's see if perf is also happy with it.

r? @ghost

Built atop #104435; will leave draft until I can rebase atop that.

@scottmcm
VecDeque::resize should re-use the buffer in the passed-in element
d62b903
Today it always copies it for *every* appended element, but one of those clones is avoidable.
@scottmcm
Hide the items while waiting for the ACP
71bb200
@scottmcm
Simplify Vec using iter::repeat_n
50b394a
By using `repeat_n` instead of `ExtendElement`, we can delete a bunch more `unsafe` code from `Vec.
All the codegen tests are passing (and I made one stricter to help be sure), so let's see if perf is also happy with it.
@rustbotrustbot added S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. T-libs Relevant to the library team, which will review and decide on the PR/issue. labels Nov 19, 2022
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@rustbotrustbot added the S-waiting-on-perf Status: Waiting on a perf run to be completed. label Nov 19, 2022
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⌛ Trying commit 50b394a with merge 30c97e84bdbff017290f6d12db34df2f225359a8...

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☀️ Try build successful - checks-actions
Build commit: 30c97e84bdbff017290f6d12db34df2f225359a8 (30c97e84bdbff017290f6d12db34df2f225359a8)

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Finished benchmarking commit (30c97e84bdbff017290f6d12db34df2f225359a8): comparison URL.

Overall result: ❌✅ regressions and improvements - ACTION NEEDED

Benchmarking this pull request likely means that it is perf-sensitive, so we're automatically marking it as not fit for rolling up. While you can manually mark this PR as fit for rollup, we strongly recommend not doing so since this PR may lead to changes in compiler perf.

Next Steps: If you can justify the regressions found in this try perf run, please indicate this with @rustbot label: +perf-regression-triaged along with sufficient written justification. If you cannot justify the regressions please fix the regressions and do another perf run. If the next run shows neutral or positive results, the label will be automatically removed.

@bors rollup=never
@rustbot label: +S-waiting-on-review -S-waiting-on-perf +perf-regression

Instruction count

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

meanrangecount
Regressions ❌
(primary)		0.4%[0.2%, 0.7%]24
Regressions ❌
(secondary)		2.3%[0.2%, 5.5%]15
Improvements ✅
(primary)		-0.8%[-1.0%, -0.6%]2
Improvements ✅
(secondary)		--0
All ❌✅ (primary)0.3%[-1.0%, 0.7%]26

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.

meanrangecount
Regressions ❌
(primary)		1.8%[0.4%, 3.8%]5
Regressions ❌
(secondary)		1.7%[1.2%, 2.5%]3
Improvements ✅
(primary)		-4.6%[-4.6%, -4.6%]1
Improvements ✅
(secondary)		--0
All ❌✅ (primary)0.8%[-4.6%, 3.8%]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.

meanrangecount
Regressions ❌
(primary)		0.8%[0.7%, 0.9%]3
Regressions ❌
(secondary)		5.0%[4.5%, 5.8%]6
Improvements ✅
(primary)		--0
Improvements ✅
(secondary)		-5.3%[-5.3%, -5.3%]1
All ❌✅ (primary)0.8%[0.7%, 0.9%]3

@rustbotrustbot added perf-regression Performance regression. and removed S-waiting-on-perf Status: Waiting on a perf run to be completed. labels Nov 19, 2022
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I'm not sure if it's a good idea to remove this. There's untapped optimization potential in the current implementation. E.g. it could use the zero-value check that vec initialization already has and then use Allocator::grow_zeroed.

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scottmcm commented Nov 19, 2022

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@the8472 I agree that's a good thing to add, but I don't think it needs the ExtendWithtrait, since we can't do that for ExtendFunc anyway. I could leave an private extend_element function without the trait and type, though, if you think that'd be helpful.

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@rustbotrustbot added the S-waiting-on-perf Status: Waiting on a perf run to be completed. label Nov 19, 2022
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⌛ Trying commit 78f2356 with merge d6ba54d913266c13b4ddf2eaf8b1b9b023df4caa...

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☀️ Try build successful - checks-actions
Build commit: d6ba54d913266c13b4ddf2eaf8b1b9b023df4caa (d6ba54d913266c13b4ddf2eaf8b1b9b023df4caa)

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Finished benchmarking commit (d6ba54d913266c13b4ddf2eaf8b1b9b023df4caa): comparison URL.

Overall result: ❌ regressions - ACTION NEEDED

Benchmarking this pull request likely means that it is perf-sensitive, so we're automatically marking it as not fit for rolling up. While you can manually mark this PR as fit for rollup, we strongly recommend not doing so since this PR may lead to changes in compiler perf.

Next Steps: If you can justify the regressions found in this try perf run, please indicate this with @rustbot label: +perf-regression-triaged along with sufficient written justification. If you cannot justify the regressions please fix the regressions and do another perf run. If the next run shows neutral or positive results, the label will be automatically removed.

@bors rollup=never
@rustbot label: +S-waiting-on-review -S-waiting-on-perf +perf-regression

Instruction count

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

meanrangecount
Regressions ❌
(primary)		0.5%[0.2%, 1.2%]76
Regressions ❌
(secondary)		1.8%[0.2%, 6.6%]30
Improvements ✅
(primary)		--0
Improvements ✅
(secondary)		-0.2%[-0.2%, -0.2%]1
All ❌✅ (primary)0.5%[0.2%, 1.2%]76

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.

meanrangecount
Regressions ❌
(primary)		1.1%[0.4%, 2.4%]6
Regressions ❌
(secondary)		1.5%[1.5%, 1.5%]1
Improvements ✅
(primary)		-4.8%[-4.8%, -4.8%]1
Improvements ✅
(secondary)		-3.7%[-5.3%, -2.1%]2
All ❌✅ (primary)0.3%[-4.8%, 2.4%]7

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.

meanrangecount
Regressions ❌
(primary)		0.9%[0.8%, 1.0%]6
Regressions ❌
(secondary)		2.5%[1.3%, 3.7%]8
Improvements ✅
(primary)		-1.4%[-1.9%, -0.9%]9
Improvements ✅
(secondary)		-2.8%[-5.2%, -2.1%]13
All ❌✅ (primary)-0.5%[-1.9%, 1.0%]15

@rustbotrustbot removed the S-waiting-on-perf Status: Waiting on a perf run to be completed. label Nov 20, 2022
@scottmcm

scottmcm commented Nov 20, 2022

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Curious -- arguably good on cycles, but clearly bad on instructions.

I guess I should do this in smaller pieces, if at all.

@scottmcm
scottmcm deleted the simplify-vec-internals branch November 20, 2022 01:02
@scottmcmscottmcm mentioned this pull request Nov 20, 2022
Closed
scottmcm added a commit to scottmcm/rust that referenced this pull request Nov 20, 2022
@scottmcm
Use normal iterators instead of the internal vec::ExtendWith
4820629
Repeating is `TrustedLen`, so we don't need another copy of [the `TrustedLen` specialization for `extend`](https://github.com/rust-lang/rust/blob/c5d82ed7a4ad94a538bb87e5016e7d5ce0bd434b/library/alloc/src/vec/spec_extend.rs#L27).
(This is a simpler version of rust-lang#104596, which tried to do too many things at once.)
@scottmcmscottmcm mentioned this pull request Dec 8, 2025
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Simplify `Vec` using `iter::repeat_n` by scottmcm · Pull Request #104596 · rust-lang/rust · GitHub
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Simplify Vec using iter::repeat_n - #104596
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scottmcm wants to merge 4 commits into
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Simplify Vec using iter::repeat_n#104596
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@scottmcmscottmcm
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Nov 19, 2022•

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By using repeat_n instead of ExtendElement, we can delete a bunch more unsafe code from Vec.
All the codegen tests are passing (and I made one stricter to help be sure), so let's see if perf is also happy with it.
r? @ghost
Built atop #104435; will leave draft until I can rebase atop that.
@scottmcm
VecDeque::resize should re-use the buffer in the passed-in element
d62b903
Today it always copies it for *every* appended element, but one of those clones is avoidable.
@scottmcm
Hide the items while waiting for the ACP
71bb200
@scottmcm
Simplify Vec using iter::repeat_n
50b394a
By using `repeat_n` instead of `ExtendElement`, we can delete a bunch more `unsafe` code from `Vec.
All the codegen tests are passing (and I made one stricter to help be sure), so let's see if perf is also happy with it.
@rustbotrustbot
added

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Status: Awaiting review from the assignee but also interested parties.
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⌛ Trying commit 50b394a with merge 30c97e84bdbff017290f6d12db34df2f225359a8...
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Nov 19, 2022

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☀️ Try build successful - checks-actions

Build commit: 30c97e84bdbff017290f6d12db34df2f225359a8 (30c97e84bdbff017290f6d12db34df2f225359a8)
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Finished benchmarking commit (30c97e84bdbff017290f6d12db34df2f225359a8): comparison URL.
Overall result: ❌✅ regressions and improvements - ACTION NEEDED
Benchmarking this pull request likely means that it is perf-sensitive, so we're automatically marking it as not fit for rolling up. While you can manually mark this PR as fit for rollup, we strongly recommend not doing so since this PR may lead to changes in compiler perf.
Next Steps: If you can justify the regressions found in this try perf run, please indicate this with @rustbot label: +perf-regression-triaged along with sufficient written justification. If you cannot justify the regressions please fix the regressions and do another perf run. If the next run shows neutral or positive results, the label will be automatically removed.
@bors rollup=never
@rustbot label: +S-waiting-on-review -S-waiting-on-perf +perf-regression
Instruction count
This is a highly reliable metric that was used to determine the overall result at the top of this comment.
meanrangecount
Regressions ❌ 
 (primary)		0.4%[0.2%, 0.7%]24
Regressions ❌ 
 (secondary)		2.3%[0.2%, 5.5%]15
Improvements ✅ 
 (primary)		-0.8%[-1.0%, -0.6%]2
Improvements ✅ 
 (secondary)		--0
All ❌✅ (primary)0.3%[-1.0%, 0.7%]26
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.
meanrangecount
Regressions ❌ 
 (primary)		1.8%[0.4%, 3.8%]5
Regressions ❌ 
 (secondary)		1.7%[1.2%, 2.5%]3
Improvements ✅ 
 (primary)		-4.6%[-4.6%, -4.6%]1
Improvements ✅ 
 (secondary)		--0
All ❌✅ (primary)0.8%[-4.6%, 3.8%]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.
meanrangecount
Regressions ❌ 
 (primary)		0.8%[0.7%, 0.9%]3
Regressions ❌ 
 (secondary)		5.0%[4.5%, 5.8%]6
Improvements ✅ 
 (primary)		--0
Improvements ✅ 
 (secondary)		-5.3%[-5.3%, -5.3%]1
All ❌✅ (primary)0.8%[0.7%, 0.9%]3
@rustbotrustbot
added

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@the8472
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I'm not sure if it's a good idea to remove this. There's untapped optimization potential in the current implementation. E.g. it could use the zero-value check that vec initialization already has and then use Allocator::grow_zeroed.
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@the8472 I agree that's a good thing to add, but I don't think it needs the ExtendWithtrait, since we can't do that for ExtendFunc anyway. I could leave an private extend_element function without the trait and type, though, if you think that'd be helpful.
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@bors try @rust-timer queue
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⌛ Trying commit 78f2356 with merge d6ba54d913266c13b4ddf2eaf8b1b9b023df4caa...
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☀️ Try build successful - checks-actions

Build commit: d6ba54d913266c13b4ddf2eaf8b1b9b023df4caa (d6ba54d913266c13b4ddf2eaf8b1b9b023df4caa)
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Finished benchmarking commit (d6ba54d913266c13b4ddf2eaf8b1b9b023df4caa): comparison URL.
Overall result: ❌ regressions - ACTION NEEDED
Benchmarking this pull request likely means that it is perf-sensitive, so we're automatically marking it as not fit for rolling up. While you can manually mark this PR as fit for rollup, we strongly recommend not doing so since this PR may lead to changes in compiler perf.
Next Steps: If you can justify the regressions found in this try perf run, please indicate this with @rustbot label: +perf-regression-triaged along with sufficient written justification. If you cannot justify the regressions please fix the regressions and do another perf run. If the next run shows neutral or positive results, the label will be automatically removed.
@bors rollup=never
@rustbot label: +S-waiting-on-review -S-waiting-on-perf +perf-regression
Instruction count
This is a highly reliable metric that was used to determine the overall result at the top of this comment.
meanrangecount
Regressions ❌ 
 (primary)		0.5%[0.2%, 1.2%]76
Regressions ❌ 
 (secondary)		1.8%[0.2%, 6.6%]30
Improvements ✅ 
 (primary)		--0
Improvements ✅ 
 (secondary)		-0.2%[-0.2%, -0.2%]1
All ❌✅ (primary)0.5%[0.2%, 1.2%]76
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.
meanrangecount
Regressions ❌ 
 (primary)		1.1%[0.4%, 2.4%]6
Regressions ❌ 
 (secondary)		1.5%[1.5%, 1.5%]1
Improvements ✅ 
 (primary)		-4.8%[-4.8%, -4.8%]1
Improvements ✅ 
 (secondary)		-3.7%[-5.3%, -2.1%]2
All ❌✅ (primary)0.3%[-4.8%, 2.4%]7
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.
meanrangecount
Regressions ❌ 
 (primary)		0.9%[0.8%, 1.0%]6
Regressions ❌ 
 (secondary)		2.5%[1.3%, 3.7%]8
Improvements ✅ 
 (primary)		-1.4%[-1.9%, -0.9%]9
Improvements ✅ 
 (secondary)		-2.8%[-5.2%, -2.1%]13
All ❌✅ (primary)-0.5%[-1.9%, 1.0%]15
@rustbotrustbot
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Status: Waiting on a perf run to be completed.
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Nov 20, 2022

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Curious -- arguably good on cycles, but clearly bad on instructions.
I guess I should do this in smaller pieces, if at all.
@scottmcm
scottmcm
deleted the

simplify-vec-internals

branch
November 20, 2022 01:02
@scottmcmscottmcm
mentioned this pull request
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to scottmcm/rust
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Nov 20, 2022
@scottmcm
Use normal iterators instead of the internal vec::ExtendWith
4820629
Repeating is `TrustedLen`, so we don't need another copy of [the `TrustedLen` specialization for `extend`](https://github.com/rust-lang/rust/blob/c5d82ed7a4ad94a538bb87e5016e7d5ce0bd434b/library/alloc/src/vec/spec_extend.rs#L27).
(This is a simpler version of rust-lang#104596, which tried to do too many things at once.)
@scottmcmscottmcm
mentioned this pull request
Dec 8, 2025
 Draft

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Simplify `Vec` using `iter::repeat_n` by scottmcm · Pull Request #104596 · rust-lang/rust · GitHub
Skip to content
Simplify Vec using iter::repeat_n - #104596
Closed
scottmcm wants to merge 4 commits into
rust-lang:masterfrom 
scottmcm:simplify-vec-internals
Closed
Simplify Vec using iter::repeat_n#104596
scottmcm wants to merge 4 commits into
rust-lang:masterfrom 
scottmcm:simplify-vec-internals
Conversation
@scottmcm
@scottmcmscottmcm
commented
Nov 19, 2022•

edited

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By using repeat_n instead of ExtendElement, we can delete a bunch more unsafe code from Vec.
All the codegen tests are passing (and I made one stricter to help be sure), so let's see if perf is also happy with it.
r? @ghost
Built atop #104435; will leave draft until I can rebase atop that.
@scottmcm
VecDeque::resize should re-use the buffer in the passed-in element
d62b903
Today it always copies it for *every* appended element, but one of those clones is avoidable.
@scottmcm
Hide the items while waiting for the ACP
71bb200
@scottmcm
Simplify Vec using iter::repeat_n
50b394a
By using `repeat_n` instead of `ExtendElement`, we can delete a bunch more `unsafe` code from `Vec.
All the codegen tests are passing (and I made one stricter to help be sure), so let's see if perf is also happy with it.
@rustbotrustbot
added

S-waiting-on-review
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⌛ Trying commit 50b394a with merge 30c97e84bdbff017290f6d12db34df2f225359a8...
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☀️ Try build successful - checks-actions

Build commit: 30c97e84bdbff017290f6d12db34df2f225359a8 (30c97e84bdbff017290f6d12db34df2f225359a8)
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Finished benchmarking commit (30c97e84bdbff017290f6d12db34df2f225359a8): comparison URL.
Overall result: ❌✅ regressions and improvements - ACTION NEEDED
Benchmarking this pull request likely means that it is perf-sensitive, so we're automatically marking it as not fit for rolling up. While you can manually mark this PR as fit for rollup, we strongly recommend not doing so since this PR may lead to changes in compiler perf.
Next Steps: If you can justify the regressions found in this try perf run, please indicate this with @rustbot label: +perf-regression-triaged along with sufficient written justification. If you cannot justify the regressions please fix the regressions and do another perf run. If the next run shows neutral or positive results, the label will be automatically removed.
@bors rollup=never
@rustbot label: +S-waiting-on-review -S-waiting-on-perf +perf-regression
Instruction count
This is a highly reliable metric that was used to determine the overall result at the top of this comment.
meanrangecount
Regressions ❌ 
 (primary)		0.4%[0.2%, 0.7%]24
Regressions ❌ 
 (secondary)		2.3%[0.2%, 5.5%]15
Improvements ✅ 
 (primary)		-0.8%[-1.0%, -0.6%]2
Improvements ✅ 
 (secondary)		--0
All ❌✅ (primary)0.3%[-1.0%, 0.7%]26
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.
meanrangecount
Regressions ❌ 
 (primary)		1.8%[0.4%, 3.8%]5
Regressions ❌ 
 (secondary)		1.7%[1.2%, 2.5%]3
Improvements ✅ 
 (primary)		-4.6%[-4.6%, -4.6%]1
Improvements ✅ 
 (secondary)		--0
All ❌✅ (primary)0.8%[-4.6%, 3.8%]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.
meanrangecount
Regressions ❌ 
 (primary)		0.8%[0.7%, 0.9%]3
Regressions ❌ 
 (secondary)		5.0%[4.5%, 5.8%]6
Improvements ✅ 
 (primary)		--0
Improvements ✅ 
 (secondary)		-5.3%[-5.3%, -5.3%]1
All ❌✅ (primary)0.8%[0.7%, 0.9%]3
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I'm not sure if it's a good idea to remove this. There's untapped optimization potential in the current implementation. E.g. it could use the zero-value check that vec initialization already has and then use Allocator::grow_zeroed.
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@the8472 I agree that's a good thing to add, but I don't think it needs the ExtendWithtrait, since we can't do that for ExtendFunc anyway. I could leave an private extend_element function without the trait and type, though, if you think that'd be helpful.
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⌛ Trying commit 78f2356 with merge d6ba54d913266c13b4ddf2eaf8b1b9b023df4caa...
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☀️ Try build successful - checks-actions

Build commit: d6ba54d913266c13b4ddf2eaf8b1b9b023df4caa (d6ba54d913266c13b4ddf2eaf8b1b9b023df4caa)
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Finished benchmarking commit (d6ba54d913266c13b4ddf2eaf8b1b9b023df4caa): comparison URL.
Overall result: ❌ regressions - ACTION NEEDED
Benchmarking this pull request likely means that it is perf-sensitive, so we're automatically marking it as not fit for rolling up. While you can manually mark this PR as fit for rollup, we strongly recommend not doing so since this PR may lead to changes in compiler perf.
Next Steps: If you can justify the regressions found in this try perf run, please indicate this with @rustbot label: +perf-regression-triaged along with sufficient written justification. If you cannot justify the regressions please fix the regressions and do another perf run. If the next run shows neutral or positive results, the label will be automatically removed.
@bors rollup=never
@rustbot label: +S-waiting-on-review -S-waiting-on-perf +perf-regression
Instruction count
This is a highly reliable metric that was used to determine the overall result at the top of this comment.
meanrangecount
Regressions ❌ 
 (primary)		0.5%[0.2%, 1.2%]76
Regressions ❌ 
 (secondary)		1.8%[0.2%, 6.6%]30
Improvements ✅ 
 (primary)		--0
Improvements ✅ 
 (secondary)		-0.2%[-0.2%, -0.2%]1
All ❌✅ (primary)0.5%[0.2%, 1.2%]76
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.
meanrangecount
Regressions ❌ 
 (primary)		1.1%[0.4%, 2.4%]6
Regressions ❌ 
 (secondary)		1.5%[1.5%, 1.5%]1
Improvements ✅ 
 (primary)		-4.8%[-4.8%, -4.8%]1
Improvements ✅ 
 (secondary)		-3.7%[-5.3%, -2.1%]2
All ❌✅ (primary)0.3%[-4.8%, 2.4%]7
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.
meanrangecount
Regressions ❌ 
 (primary)		0.9%[0.8%, 1.0%]6
Regressions ❌ 
 (secondary)		2.5%[1.3%, 3.7%]8
Improvements ✅ 
 (primary)		-1.4%[-1.9%, -0.9%]9
Improvements ✅ 
 (secondary)		-2.8%[-5.2%, -2.1%]13
All ❌✅ (primary)-0.5%[-1.9%, 1.0%]15
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Curious -- arguably good on cycles, but clearly bad on instructions.
I guess I should do this in smaller pieces, if at all.
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Use normal iterators instead of the internal vec::ExtendWith
4820629
Repeating is `TrustedLen`, so we don't need another copy of [the `TrustedLen` specialization for `extend`](https://github.com/rust-lang/rust/blob/c5d82ed7a4ad94a538bb87e5016e7d5ce0bd434b/library/alloc/src/vec/spec_extend.rs#L27).
(This is a simpler version of rust-lang#104596, which tried to do too many things at once.)
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Simplify `Vec` using `iter::repeat_n` by scottmcm · Pull Request #104596 · rust-lang/rust · GitHub
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Simplify Vec using iter::repeat_n - #104596
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By using repeat_n instead of ExtendElement, we can delete a bunch more unsafe code from Vec.
All the codegen tests are passing (and I made one stricter to help be sure), so let's see if perf is also happy with it.
r? @ghost
Built atop #104435; will leave draft until I can rebase atop that.
@scottmcm
VecDeque::resize should re-use the buffer in the passed-in element
d62b903
Today it always copies it for *every* appended element, but one of those clones is avoidable.
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Hide the items while waiting for the ACP
71bb200
@scottmcm
Simplify Vec using iter::repeat_n
50b394a
By using `repeat_n` instead of `ExtendElement`, we can delete a bunch more `unsafe` code from `Vec.
All the codegen tests are passing (and I made one stricter to help be sure), so let's see if perf is also happy with it.
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⌛ Trying commit 50b394a with merge 30c97e84bdbff017290f6d12db34df2f225359a8...
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☀️ Try build successful - checks-actions

Build commit: 30c97e84bdbff017290f6d12db34df2f225359a8 (30c97e84bdbff017290f6d12db34df2f225359a8)
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Finished benchmarking commit (30c97e84bdbff017290f6d12db34df2f225359a8): comparison URL.
Overall result: ❌✅ regressions and improvements - ACTION NEEDED
Benchmarking this pull request likely means that it is perf-sensitive, so we're automatically marking it as not fit for rolling up. While you can manually mark this PR as fit for rollup, we strongly recommend not doing so since this PR may lead to changes in compiler perf.
Next Steps: If you can justify the regressions found in this try perf run, please indicate this with @rustbot label: +perf-regression-triaged along with sufficient written justification. If you cannot justify the regressions please fix the regressions and do another perf run. If the next run shows neutral or positive results, the label will be automatically removed.
@bors rollup=never
@rustbot label: +S-waiting-on-review -S-waiting-on-perf +perf-regression
Instruction count
This is a highly reliable metric that was used to determine the overall result at the top of this comment.
meanrangecount
Regressions ❌ 
 (primary)		0.4%[0.2%, 0.7%]24
Regressions ❌ 
 (secondary)		2.3%[0.2%, 5.5%]15
Improvements ✅ 
 (primary)		-0.8%[-1.0%, -0.6%]2
Improvements ✅ 
 (secondary)		--0
All ❌✅ (primary)0.3%[-1.0%, 0.7%]26
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.
meanrangecount
Regressions ❌ 
 (primary)		1.8%[0.4%, 3.8%]5
Regressions ❌ 
 (secondary)		1.7%[1.2%, 2.5%]3
Improvements ✅ 
 (primary)		-4.6%[-4.6%, -4.6%]1
Improvements ✅ 
 (secondary)		--0
All ❌✅ (primary)0.8%[-4.6%, 3.8%]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.
meanrangecount
Regressions ❌ 
 (primary)		0.8%[0.7%, 0.9%]3
Regressions ❌ 
 (secondary)		5.0%[4.5%, 5.8%]6
Improvements ✅ 
 (primary)		--0
Improvements ✅ 
 (secondary)		-5.3%[-5.3%, -5.3%]1
All ❌✅ (primary)0.8%[0.7%, 0.9%]3
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I'm not sure if it's a good idea to remove this. There's untapped optimization potential in the current implementation. E.g. it could use the zero-value check that vec initialization already has and then use Allocator::grow_zeroed.
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@the8472 I agree that's a good thing to add, but I don't think it needs the ExtendWithtrait, since we can't do that for ExtendFunc anyway. I could leave an private extend_element function without the trait and type, though, if you think that'd be helpful.
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⌛ Trying commit 78f2356 with merge d6ba54d913266c13b4ddf2eaf8b1b9b023df4caa...
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☀️ Try build successful - checks-actions

Build commit: d6ba54d913266c13b4ddf2eaf8b1b9b023df4caa (d6ba54d913266c13b4ddf2eaf8b1b9b023df4caa)
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Finished benchmarking commit (d6ba54d913266c13b4ddf2eaf8b1b9b023df4caa): comparison URL.
Overall result: ❌ regressions - ACTION NEEDED
Benchmarking this pull request likely means that it is perf-sensitive, so we're automatically marking it as not fit for rolling up. While you can manually mark this PR as fit for rollup, we strongly recommend not doing so since this PR may lead to changes in compiler perf.
Next Steps: If you can justify the regressions found in this try perf run, please indicate this with @rustbot label: +perf-regression-triaged along with sufficient written justification. If you cannot justify the regressions please fix the regressions and do another perf run. If the next run shows neutral or positive results, the label will be automatically removed.
@bors rollup=never
@rustbot label: +S-waiting-on-review -S-waiting-on-perf +perf-regression
Instruction count
This is a highly reliable metric that was used to determine the overall result at the top of this comment.
meanrangecount
Regressions ❌ 
 (primary)		0.5%[0.2%, 1.2%]76
Regressions ❌ 
 (secondary)		1.8%[0.2%, 6.6%]30
Improvements ✅ 
 (primary)		--0
Improvements ✅ 
 (secondary)		-0.2%[-0.2%, -0.2%]1
All ❌✅ (primary)0.5%[0.2%, 1.2%]76
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.
meanrangecount
Regressions ❌ 
 (primary)		1.1%[0.4%, 2.4%]6
Regressions ❌ 
 (secondary)		1.5%[1.5%, 1.5%]1
Improvements ✅ 
 (primary)		-4.8%[-4.8%, -4.8%]1
Improvements ✅ 
 (secondary)		-3.7%[-5.3%, -2.1%]2
All ❌✅ (primary)0.3%[-4.8%, 2.4%]7
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.
meanrangecount
Regressions ❌ 
 (primary)		0.9%[0.8%, 1.0%]6
Regressions ❌ 
 (secondary)		2.5%[1.3%, 3.7%]8
Improvements ✅ 
 (primary)		-1.4%[-1.9%, -0.9%]9
Improvements ✅ 
 (secondary)		-2.8%[-5.2%, -2.1%]13
All ❌✅ (primary)-0.5%[-1.9%, 1.0%]15
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Curious -- arguably good on cycles, but clearly bad on instructions.
I guess I should do this in smaller pieces, if at all.
@scottmcm
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November 20, 2022 01:02
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@scottmcm
Use normal iterators instead of the internal vec::ExtendWith
4820629
Repeating is `TrustedLen`, so we don't need another copy of [the `TrustedLen` specialization for `extend`](https://github.com/rust-lang/rust/blob/c5d82ed7a4ad94a538bb87e5016e7d5ce0bd434b/library/alloc/src/vec/spec_extend.rs#L27).
(This is a simpler version of rust-lang#104596, which tried to do too many things at once.)
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Simplify `Vec` using `iter::repeat_n` by scottmcm · Pull Request #104596 · rust-lang/rust · GitHub
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Simplify Vec using iter::repeat_n - #104596
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Simplify Vec using iter::repeat_n#104596
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By using repeat_n instead of ExtendElement, we can delete a bunch more unsafe code from Vec.
All the codegen tests are passing (and I made one stricter to help be sure), so let's see if perf is also happy with it.
r? @ghost
Built atop #104435; will leave draft until I can rebase atop that.
@scottmcm
VecDeque::resize should re-use the buffer in the passed-in element
d62b903
Today it always copies it for *every* appended element, but one of those clones is avoidable.
@scottmcm
Hide the items while waiting for the ACP
71bb200
@scottmcm
Simplify Vec using iter::repeat_n
50b394a
By using `repeat_n` instead of `ExtendElement`, we can delete a bunch more `unsafe` code from `Vec.
All the codegen tests are passing (and I made one stricter to help be sure), so let's see if perf is also happy with it.
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⌛ Trying commit 50b394a with merge 30c97e84bdbff017290f6d12db34df2f225359a8...
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☀️ Try build successful - checks-actions

Build commit: 30c97e84bdbff017290f6d12db34df2f225359a8 (30c97e84bdbff017290f6d12db34df2f225359a8)
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Finished benchmarking commit (30c97e84bdbff017290f6d12db34df2f225359a8): comparison URL.
Overall result: ❌✅ regressions and improvements - ACTION NEEDED
Benchmarking this pull request likely means that it is perf-sensitive, so we're automatically marking it as not fit for rolling up. While you can manually mark this PR as fit for rollup, we strongly recommend not doing so since this PR may lead to changes in compiler perf.
Next Steps: If you can justify the regressions found in this try perf run, please indicate this with @rustbot label: +perf-regression-triaged along with sufficient written justification. If you cannot justify the regressions please fix the regressions and do another perf run. If the next run shows neutral or positive results, the label will be automatically removed.
@bors rollup=never
@rustbot label: +S-waiting-on-review -S-waiting-on-perf +perf-regression
Instruction count
This is a highly reliable metric that was used to determine the overall result at the top of this comment.
meanrangecount
Regressions ❌ 
 (primary)		0.4%[0.2%, 0.7%]24
Regressions ❌ 
 (secondary)		2.3%[0.2%, 5.5%]15
Improvements ✅ 
 (primary)		-0.8%[-1.0%, -0.6%]2
Improvements ✅ 
 (secondary)		--0
All ❌✅ (primary)0.3%[-1.0%, 0.7%]26
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.
meanrangecount
Regressions ❌ 
 (primary)		1.8%[0.4%, 3.8%]5
Regressions ❌ 
 (secondary)		1.7%[1.2%, 2.5%]3
Improvements ✅ 
 (primary)		-4.6%[-4.6%, -4.6%]1
Improvements ✅ 
 (secondary)		--0
All ❌✅ (primary)0.8%[-4.6%, 3.8%]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.
meanrangecount
Regressions ❌ 
 (primary)		0.8%[0.7%, 0.9%]3
Regressions ❌ 
 (secondary)		5.0%[4.5%, 5.8%]6
Improvements ✅ 
 (primary)		--0
Improvements ✅ 
 (secondary)		-5.3%[-5.3%, -5.3%]1
All ❌✅ (primary)0.8%[0.7%, 0.9%]3
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I'm not sure if it's a good idea to remove this. There's untapped optimization potential in the current implementation. E.g. it could use the zero-value check that vec initialization already has and then use Allocator::grow_zeroed.
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@the8472 I agree that's a good thing to add, but I don't think it needs the ExtendWithtrait, since we can't do that for ExtendFunc anyway. I could leave an private extend_element function without the trait and type, though, if you think that'd be helpful.
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⌛ Trying commit 78f2356 with merge d6ba54d913266c13b4ddf2eaf8b1b9b023df4caa...
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☀️ Try build successful - checks-actions

Build commit: d6ba54d913266c13b4ddf2eaf8b1b9b023df4caa (d6ba54d913266c13b4ddf2eaf8b1b9b023df4caa)
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Finished benchmarking commit (d6ba54d913266c13b4ddf2eaf8b1b9b023df4caa): comparison URL.
Overall result: ❌ regressions - ACTION NEEDED
Benchmarking this pull request likely means that it is perf-sensitive, so we're automatically marking it as not fit for rolling up. While you can manually mark this PR as fit for rollup, we strongly recommend not doing so since this PR may lead to changes in compiler perf.
Next Steps: If you can justify the regressions found in this try perf run, please indicate this with @rustbot label: +perf-regression-triaged along with sufficient written justification. If you cannot justify the regressions please fix the regressions and do another perf run. If the next run shows neutral or positive results, the label will be automatically removed.
@bors rollup=never
@rustbot label: +S-waiting-on-review -S-waiting-on-perf +perf-regression
Instruction count
This is a highly reliable metric that was used to determine the overall result at the top of this comment.
meanrangecount
Regressions ❌ 
 (primary)		0.5%[0.2%, 1.2%]76
Regressions ❌ 
 (secondary)		1.8%[0.2%, 6.6%]30
Improvements ✅ 
 (primary)		--0
Improvements ✅ 
 (secondary)		-0.2%[-0.2%, -0.2%]1
All ❌✅ (primary)0.5%[0.2%, 1.2%]76
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.
meanrangecount
Regressions ❌ 
 (primary)		1.1%[0.4%, 2.4%]6
Regressions ❌ 
 (secondary)		1.5%[1.5%, 1.5%]1
Improvements ✅ 
 (primary)		-4.8%[-4.8%, -4.8%]1
Improvements ✅ 
 (secondary)		-3.7%[-5.3%, -2.1%]2
All ❌✅ (primary)0.3%[-4.8%, 2.4%]7
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.
meanrangecount
Regressions ❌ 
 (primary)		0.9%[0.8%, 1.0%]6
Regressions ❌ 
 (secondary)		2.5%[1.3%, 3.7%]8
Improvements ✅ 
 (primary)		-1.4%[-1.9%, -0.9%]9
Improvements ✅ 
 (secondary)		-2.8%[-5.2%, -2.1%]13
All ❌✅ (primary)-0.5%[-1.9%, 1.0%]15
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Curious -- arguably good on cycles, but clearly bad on instructions.
I guess I should do this in smaller pieces, if at all.
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Use normal iterators instead of the internal vec::ExtendWith
4820629
Repeating is `TrustedLen`, so we don't need another copy of [the `TrustedLen` specialization for `extend`](https://github.com/rust-lang/rust/blob/c5d82ed7a4ad94a538bb87e5016e7d5ce0bd434b/library/alloc/src/vec/spec_extend.rs#L27).
(This is a simpler version of rust-lang#104596, which tried to do too many things at once.)
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Simplify `Vec` using `iter::repeat_n` by scottmcm · Pull Request #104596 · rust-lang/rust · GitHub
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Simplify Vec using iter::repeat_n - #104596
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Simplify Vec using iter::repeat_n#104596
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Nov 19, 2022•

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By using repeat_n instead of ExtendElement, we can delete a bunch more unsafe code from Vec.
All the codegen tests are passing (and I made one stricter to help be sure), so let's see if perf is also happy with it.
r? @ghost
Built atop #104435; will leave draft until I can rebase atop that.
@scottmcm
VecDeque::resize should re-use the buffer in the passed-in element
d62b903
Today it always copies it for *every* appended element, but one of those clones is avoidable.
@scottmcm
Hide the items while waiting for the ACP
71bb200
@scottmcm
Simplify Vec using iter::repeat_n
50b394a
By using `repeat_n` instead of `ExtendElement`, we can delete a bunch more `unsafe` code from `Vec.
All the codegen tests are passing (and I made one stricter to help be sure), so let's see if perf is also happy with it.
@rustbotrustbot
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⌛ Trying commit 50b394a with merge 30c97e84bdbff017290f6d12db34df2f225359a8...
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☀️ Try build successful - checks-actions

Build commit: 30c97e84bdbff017290f6d12db34df2f225359a8 (30c97e84bdbff017290f6d12db34df2f225359a8)
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Finished benchmarking commit (30c97e84bdbff017290f6d12db34df2f225359a8): comparison URL.
Overall result: ❌✅ regressions and improvements - ACTION NEEDED
Benchmarking this pull request likely means that it is perf-sensitive, so we're automatically marking it as not fit for rolling up. While you can manually mark this PR as fit for rollup, we strongly recommend not doing so since this PR may lead to changes in compiler perf.
Next Steps: If you can justify the regressions found in this try perf run, please indicate this with @rustbot label: +perf-regression-triaged along with sufficient written justification. If you cannot justify the regressions please fix the regressions and do another perf run. If the next run shows neutral or positive results, the label will be automatically removed.
@bors rollup=never
@rustbot label: +S-waiting-on-review -S-waiting-on-perf +perf-regression
Instruction count
This is a highly reliable metric that was used to determine the overall result at the top of this comment.
meanrangecount
Regressions ❌ 
 (primary)		0.4%[0.2%, 0.7%]24
Regressions ❌ 
 (secondary)		2.3%[0.2%, 5.5%]15
Improvements ✅ 
 (primary)		-0.8%[-1.0%, -0.6%]2
Improvements ✅ 
 (secondary)		--0
All ❌✅ (primary)0.3%[-1.0%, 0.7%]26
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.
meanrangecount
Regressions ❌ 
 (primary)		1.8%[0.4%, 3.8%]5
Regressions ❌ 
 (secondary)		1.7%[1.2%, 2.5%]3
Improvements ✅ 
 (primary)		-4.6%[-4.6%, -4.6%]1
Improvements ✅ 
 (secondary)		--0
All ❌✅ (primary)0.8%[-4.6%, 3.8%]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.
meanrangecount
Regressions ❌ 
 (primary)		0.8%[0.7%, 0.9%]3
Regressions ❌ 
 (secondary)		5.0%[4.5%, 5.8%]6
Improvements ✅ 
 (primary)		--0
Improvements ✅ 
 (secondary)		-5.3%[-5.3%, -5.3%]1
All ❌✅ (primary)0.8%[0.7%, 0.9%]3
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@the8472
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I'm not sure if it's a good idea to remove this. There's untapped optimization potential in the current implementation. E.g. it could use the zero-value check that vec initialization already has and then use Allocator::grow_zeroed.
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@the8472 I agree that's a good thing to add, but I don't think it needs the ExtendWithtrait, since we can't do that for ExtendFunc anyway. I could leave an private extend_element function without the trait and type, though, if you think that'd be helpful.
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⌛ Trying commit 78f2356 with merge d6ba54d913266c13b4ddf2eaf8b1b9b023df4caa...
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☀️ Try build successful - checks-actions

Build commit: d6ba54d913266c13b4ddf2eaf8b1b9b023df4caa (d6ba54d913266c13b4ddf2eaf8b1b9b023df4caa)
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Finished benchmarking commit (d6ba54d913266c13b4ddf2eaf8b1b9b023df4caa): comparison URL.
Overall result: ❌ regressions - ACTION NEEDED
Benchmarking this pull request likely means that it is perf-sensitive, so we're automatically marking it as not fit for rolling up. While you can manually mark this PR as fit for rollup, we strongly recommend not doing so since this PR may lead to changes in compiler perf.
Next Steps: If you can justify the regressions found in this try perf run, please indicate this with @rustbot label: +perf-regression-triaged along with sufficient written justification. If you cannot justify the regressions please fix the regressions and do another perf run. If the next run shows neutral or positive results, the label will be automatically removed.
@bors rollup=never
@rustbot label: +S-waiting-on-review -S-waiting-on-perf +perf-regression
Instruction count
This is a highly reliable metric that was used to determine the overall result at the top of this comment.
meanrangecount
Regressions ❌ 
 (primary)		0.5%[0.2%, 1.2%]76
Regressions ❌ 
 (secondary)		1.8%[0.2%, 6.6%]30
Improvements ✅ 
 (primary)		--0
Improvements ✅ 
 (secondary)		-0.2%[-0.2%, -0.2%]1
All ❌✅ (primary)0.5%[0.2%, 1.2%]76
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.
meanrangecount
Regressions ❌ 
 (primary)		1.1%[0.4%, 2.4%]6
Regressions ❌ 
 (secondary)		1.5%[1.5%, 1.5%]1
Improvements ✅ 
 (primary)		-4.8%[-4.8%, -4.8%]1
Improvements ✅ 
 (secondary)		-3.7%[-5.3%, -2.1%]2
All ❌✅ (primary)0.3%[-4.8%, 2.4%]7
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.
meanrangecount
Regressions ❌ 
 (primary)		0.9%[0.8%, 1.0%]6
Regressions ❌ 
 (secondary)		2.5%[1.3%, 3.7%]8
Improvements ✅ 
 (primary)		-1.4%[-1.9%, -0.9%]9
Improvements ✅ 
 (secondary)		-2.8%[-5.2%, -2.1%]13
All ❌✅ (primary)-0.5%[-1.9%, 1.0%]15
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Curious -- arguably good on cycles, but clearly bad on instructions.
I guess I should do this in smaller pieces, if at all.
@scottmcm
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November 20, 2022 01:02
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@scottmcm
Use normal iterators instead of the internal vec::ExtendWith
4820629
Repeating is `TrustedLen`, so we don't need another copy of [the `TrustedLen` specialization for `extend`](https://github.com/rust-lang/rust/blob/c5d82ed7a4ad94a538bb87e5016e7d5ce0bd434b/library/alloc/src/vec/spec_extend.rs#L27).
(This is a simpler version of rust-lang#104596, which tried to do too many things at once.)
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Simplify `Vec` using `iter::repeat_n` by scottmcm · Pull Request #104596 · rust-lang/rust · GitHub
Skip to content
Simplify Vec using iter::repeat_n - #104596
Closed
scottmcm wants to merge 4 commits into
rust-lang:masterfrom 
scottmcm:simplify-vec-internals
Closed
Simplify Vec using iter::repeat_n#104596
scottmcm wants to merge 4 commits into
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scottmcm:simplify-vec-internals
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Nov 19, 2022•

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By using repeat_n instead of ExtendElement, we can delete a bunch more unsafe code from Vec.
All the codegen tests are passing (and I made one stricter to help be sure), so let's see if perf is also happy with it.
r? @ghost
Built atop #104435; will leave draft until I can rebase atop that.
@scottmcm
VecDeque::resize should re-use the buffer in the passed-in element
d62b903
Today it always copies it for *every* appended element, but one of those clones is avoidable.
@scottmcm
Hide the items while waiting for the ACP
71bb200
@scottmcm
Simplify Vec using iter::repeat_n
50b394a
By using `repeat_n` instead of `ExtendElement`, we can delete a bunch more `unsafe` code from `Vec.
All the codegen tests are passing (and I made one stricter to help be sure), so let's see if perf is also happy with it.
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⌛ Trying commit 50b394a with merge 30c97e84bdbff017290f6d12db34df2f225359a8...
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☀️ Try build successful - checks-actions

Build commit: 30c97e84bdbff017290f6d12db34df2f225359a8 (30c97e84bdbff017290f6d12db34df2f225359a8)
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Finished benchmarking commit (30c97e84bdbff017290f6d12db34df2f225359a8): comparison URL.
Overall result: ❌✅ regressions and improvements - ACTION NEEDED
Benchmarking this pull request likely means that it is perf-sensitive, so we're automatically marking it as not fit for rolling up. While you can manually mark this PR as fit for rollup, we strongly recommend not doing so since this PR may lead to changes in compiler perf.
Next Steps: If you can justify the regressions found in this try perf run, please indicate this with @rustbot label: +perf-regression-triaged along with sufficient written justification. If you cannot justify the regressions please fix the regressions and do another perf run. If the next run shows neutral or positive results, the label will be automatically removed.
@bors rollup=never
@rustbot label: +S-waiting-on-review -S-waiting-on-perf +perf-regression
Instruction count
This is a highly reliable metric that was used to determine the overall result at the top of this comment.
meanrangecount
Regressions ❌ 
 (primary)		0.4%[0.2%, 0.7%]24
Regressions ❌ 
 (secondary)		2.3%[0.2%, 5.5%]15
Improvements ✅ 
 (primary)		-0.8%[-1.0%, -0.6%]2
Improvements ✅ 
 (secondary)		--0
All ❌✅ (primary)0.3%[-1.0%, 0.7%]26
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.
meanrangecount
Regressions ❌ 
 (primary)		1.8%[0.4%, 3.8%]5
Regressions ❌ 
 (secondary)		1.7%[1.2%, 2.5%]3
Improvements ✅ 
 (primary)		-4.6%[-4.6%, -4.6%]1
Improvements ✅ 
 (secondary)		--0
All ❌✅ (primary)0.8%[-4.6%, 3.8%]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.
meanrangecount
Regressions ❌ 
 (primary)		0.8%[0.7%, 0.9%]3
Regressions ❌ 
 (secondary)		5.0%[4.5%, 5.8%]6
Improvements ✅ 
 (primary)		--0
Improvements ✅ 
 (secondary)		-5.3%[-5.3%, -5.3%]1
All ❌✅ (primary)0.8%[0.7%, 0.9%]3
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I'm not sure if it's a good idea to remove this. There's untapped optimization potential in the current implementation. E.g. it could use the zero-value check that vec initialization already has and then use Allocator::grow_zeroed.
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@the8472 I agree that's a good thing to add, but I don't think it needs the ExtendWithtrait, since we can't do that for ExtendFunc anyway. I could leave an private extend_element function without the trait and type, though, if you think that'd be helpful.
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@bors try @rust-timer queue
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⌛ Trying commit 78f2356 with merge d6ba54d913266c13b4ddf2eaf8b1b9b023df4caa...
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☀️ Try build successful - checks-actions

Build commit: d6ba54d913266c13b4ddf2eaf8b1b9b023df4caa (d6ba54d913266c13b4ddf2eaf8b1b9b023df4caa)
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Finished benchmarking commit (d6ba54d913266c13b4ddf2eaf8b1b9b023df4caa): comparison URL.
Overall result: ❌ regressions - ACTION NEEDED
Benchmarking this pull request likely means that it is perf-sensitive, so we're automatically marking it as not fit for rolling up. While you can manually mark this PR as fit for rollup, we strongly recommend not doing so since this PR may lead to changes in compiler perf.
Next Steps: If you can justify the regressions found in this try perf run, please indicate this with @rustbot label: +perf-regression-triaged along with sufficient written justification. If you cannot justify the regressions please fix the regressions and do another perf run. If the next run shows neutral or positive results, the label will be automatically removed.
@bors rollup=never
@rustbot label: +S-waiting-on-review -S-waiting-on-perf +perf-regression
Instruction count
This is a highly reliable metric that was used to determine the overall result at the top of this comment.
meanrangecount
Regressions ❌ 
 (primary)		0.5%[0.2%, 1.2%]76
Regressions ❌ 
 (secondary)		1.8%[0.2%, 6.6%]30
Improvements ✅ 
 (primary)		--0
Improvements ✅ 
 (secondary)		-0.2%[-0.2%, -0.2%]1
All ❌✅ (primary)0.5%[0.2%, 1.2%]76
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.
meanrangecount
Regressions ❌ 
 (primary)		1.1%[0.4%, 2.4%]6
Regressions ❌ 
 (secondary)		1.5%[1.5%, 1.5%]1
Improvements ✅ 
 (primary)		-4.8%[-4.8%, -4.8%]1
Improvements ✅ 
 (secondary)		-3.7%[-5.3%, -2.1%]2
All ❌✅ (primary)0.3%[-4.8%, 2.4%]7
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.
meanrangecount
Regressions ❌ 
 (primary)		0.9%[0.8%, 1.0%]6
Regressions ❌ 
 (secondary)		2.5%[1.3%, 3.7%]8
Improvements ✅ 
 (primary)		-1.4%[-1.9%, -0.9%]9
Improvements ✅ 
 (secondary)		-2.8%[-5.2%, -2.1%]13
All ❌✅ (primary)-0.5%[-1.9%, 1.0%]15
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Curious -- arguably good on cycles, but clearly bad on instructions.
I guess I should do this in smaller pieces, if at all.
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Use normal iterators instead of the internal vec::ExtendWith
4820629
Repeating is `TrustedLen`, so we don't need another copy of [the `TrustedLen` specialization for `extend`](https://github.com/rust-lang/rust/blob/c5d82ed7a4ad94a538bb87e5016e7d5ce0bd434b/library/alloc/src/vec/spec_extend.rs#L27).
(This is a simpler version of rust-lang#104596, which tried to do too many things at once.)
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Simplify `Vec` using `iter::repeat_n` by scottmcm · Pull Request #104596 · rust-lang/rust · GitHub
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Simplify Vec using iter::repeat_n - #104596
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Nov 19, 2022•

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By using repeat_n instead of ExtendElement, we can delete a bunch more unsafe code from Vec.
All the codegen tests are passing (and I made one stricter to help be sure), so let's see if perf is also happy with it.
r? @ghost
Built atop #104435; will leave draft until I can rebase atop that.
@scottmcm
VecDeque::resize should re-use the buffer in the passed-in element
d62b903
Today it always copies it for *every* appended element, but one of those clones is avoidable.
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Hide the items while waiting for the ACP
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@scottmcm
Simplify Vec using iter::repeat_n
50b394a
By using `repeat_n` instead of `ExtendElement`, we can delete a bunch more `unsafe` code from `Vec.
All the codegen tests are passing (and I made one stricter to help be sure), so let's see if perf is also happy with it.
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⌛ Trying commit 50b394a with merge 30c97e84bdbff017290f6d12db34df2f225359a8...
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☀️ Try build successful - checks-actions

Build commit: 30c97e84bdbff017290f6d12db34df2f225359a8 (30c97e84bdbff017290f6d12db34df2f225359a8)
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Finished benchmarking commit (30c97e84bdbff017290f6d12db34df2f225359a8): comparison URL.
Overall result: ❌✅ regressions and improvements - ACTION NEEDED
Benchmarking this pull request likely means that it is perf-sensitive, so we're automatically marking it as not fit for rolling up. While you can manually mark this PR as fit for rollup, we strongly recommend not doing so since this PR may lead to changes in compiler perf.
Next Steps: If you can justify the regressions found in this try perf run, please indicate this with @rustbot label: +perf-regression-triaged along with sufficient written justification. If you cannot justify the regressions please fix the regressions and do another perf run. If the next run shows neutral or positive results, the label will be automatically removed.
@bors rollup=never
@rustbot label: +S-waiting-on-review -S-waiting-on-perf +perf-regression
Instruction count
This is a highly reliable metric that was used to determine the overall result at the top of this comment.
meanrangecount
Regressions ❌ 
 (primary)		0.4%[0.2%, 0.7%]24
Regressions ❌ 
 (secondary)		2.3%[0.2%, 5.5%]15
Improvements ✅ 
 (primary)		-0.8%[-1.0%, -0.6%]2
Improvements ✅ 
 (secondary)		--0
All ❌✅ (primary)0.3%[-1.0%, 0.7%]26
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.
meanrangecount
Regressions ❌ 
 (primary)		1.8%[0.4%, 3.8%]5
Regressions ❌ 
 (secondary)		1.7%[1.2%, 2.5%]3
Improvements ✅ 
 (primary)		-4.6%[-4.6%, -4.6%]1
Improvements ✅ 
 (secondary)		--0
All ❌✅ (primary)0.8%[-4.6%, 3.8%]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.
meanrangecount
Regressions ❌ 
 (primary)		0.8%[0.7%, 0.9%]3
Regressions ❌ 
 (secondary)		5.0%[4.5%, 5.8%]6
Improvements ✅ 
 (primary)		--0
Improvements ✅ 
 (secondary)		-5.3%[-5.3%, -5.3%]1
All ❌✅ (primary)0.8%[0.7%, 0.9%]3
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I'm not sure if it's a good idea to remove this. There's untapped optimization potential in the current implementation. E.g. it could use the zero-value check that vec initialization already has and then use Allocator::grow_zeroed.
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@the8472 I agree that's a good thing to add, but I don't think it needs the ExtendWithtrait, since we can't do that for ExtendFunc anyway. I could leave an private extend_element function without the trait and type, though, if you think that'd be helpful.
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⌛ Trying commit 78f2356 with merge d6ba54d913266c13b4ddf2eaf8b1b9b023df4caa...
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☀️ Try build successful - checks-actions

Build commit: d6ba54d913266c13b4ddf2eaf8b1b9b023df4caa (d6ba54d913266c13b4ddf2eaf8b1b9b023df4caa)
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Finished benchmarking commit (d6ba54d913266c13b4ddf2eaf8b1b9b023df4caa): comparison URL.
Overall result: ❌ regressions - ACTION NEEDED
Benchmarking this pull request likely means that it is perf-sensitive, so we're automatically marking it as not fit for rolling up. While you can manually mark this PR as fit for rollup, we strongly recommend not doing so since this PR may lead to changes in compiler perf.
Next Steps: If you can justify the regressions found in this try perf run, please indicate this with @rustbot label: +perf-regression-triaged along with sufficient written justification. If you cannot justify the regressions please fix the regressions and do another perf run. If the next run shows neutral or positive results, the label will be automatically removed.
@bors rollup=never
@rustbot label: +S-waiting-on-review -S-waiting-on-perf +perf-regression
Instruction count
This is a highly reliable metric that was used to determine the overall result at the top of this comment.
meanrangecount
Regressions ❌ 
 (primary)		0.5%[0.2%, 1.2%]76
Regressions ❌ 
 (secondary)		1.8%[0.2%, 6.6%]30
Improvements ✅ 
 (primary)		--0
Improvements ✅ 
 (secondary)		-0.2%[-0.2%, -0.2%]1
All ❌✅ (primary)0.5%[0.2%, 1.2%]76
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.
meanrangecount
Regressions ❌ 
 (primary)		1.1%[0.4%, 2.4%]6
Regressions ❌ 
 (secondary)		1.5%[1.5%, 1.5%]1
Improvements ✅ 
 (primary)		-4.8%[-4.8%, -4.8%]1
Improvements ✅ 
 (secondary)		-3.7%[-5.3%, -2.1%]2
All ❌✅ (primary)0.3%[-4.8%, 2.4%]7
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.
meanrangecount
Regressions ❌ 
 (primary)		0.9%[0.8%, 1.0%]6
Regressions ❌ 
 (secondary)		2.5%[1.3%, 3.7%]8
Improvements ✅ 
 (primary)		-1.4%[-1.9%, -0.9%]9
Improvements ✅ 
 (secondary)		-2.8%[-5.2%, -2.1%]13
All ❌✅ (primary)-0.5%[-1.9%, 1.0%]15
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Curious -- arguably good on cycles, but clearly bad on instructions.
I guess I should do this in smaller pieces, if at all.
@scottmcm
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simplify-vec-internals

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November 20, 2022 01:02
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scottmcm added a commit
to scottmcm/rust
that referenced
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Nov 20, 2022
@scottmcm
Use normal iterators instead of the internal vec::ExtendWith
4820629
Repeating is `TrustedLen`, so we don't need another copy of [the `TrustedLen` specialization for `extend`](https://github.com/rust-lang/rust/blob/c5d82ed7a4ad94a538bb87e5016e7d5ce0bd434b/library/alloc/src/vec/spec_extend.rs#L27).
(This is a simpler version of rust-lang#104596, which tried to do too many things at once.)
@scottmcmscottmcm
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Dec 8, 2025
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