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Use bitset for locals_with_use_data - #161476

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Use bitset for locals_with_use_data#161476
panstromek wants to merge 1 commit into
rust-lang:mainfrom
panstromek:use-bitset-locals-with-use-data

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@panstromek panstromek commented Aug 21, 2026 •
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There seems to be very little reason to use Vec of bools, the whole map allocates space for every element anyway.

Not sure how is impactful this is, I noticed it randomly in the code, but this seems like cleaner way to do it (and more common in the compiler codebase)

@rustbot rustbot added S-waiting-on-author Status: This is awaiting some action (such as code changes or more information) from the author. T-compiler Relevant to the compiler team, which will review and decide on the PR/issue. labels Aug 21, 2026
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Use bitset for locals_with_use_data
823b923 
There seems to be very little reason to use Vec of bools, the whole map allocates space for every element anyway.
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panstromek force-pushed the use-bitset-locals-with-use-data branch from 2220f48 to 823b923 Compare August 21, 2026 17:36
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panstromek commented Aug 21, 2026

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Let's check just in case

@bors try @rust-timer queue

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@rustbot rustbot added the S-waiting-on-perf Status: Waiting on a perf run to be completed. label Aug 21, 2026
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rust-bors Bot pushed a commit that referenced this pull request Aug 21, 2026
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Auto merge of #161476 - panstromek:use-bitset-locals-with-use-data, r…
43bc7f3 
…=<try>

Use bitset for locals_with_use_data
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☀️ Try build successful (CI)
Build commit: 43bc7f3 (43bc7f388e0ac4d2209ef1c38e8641b380cbbc9c)
Base parent: b662191 (b66219142c937562f2ff8e083be2a2b25b20199e)

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@lqd

lqd commented Aug 21, 2026

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(check out #141325 if you like bitsets and want to push this one to completion)

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panstromek commented Aug 21, 2026

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Yes, I've that one in mind, too (as well as the other 2-3 bitset experiments since then). I'm trying to enable that with slightly different approach to avoid internal branching in #161345 and #161454, but it's still very WIP

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Finished benchmarking commit (43bc7f3): comparison URL.

Overall result: no relevant changes - no action needed

Benchmarking means the PR may be perf-sensitive. Consider adding rollup=never if this change is not fit for rolling up.

@rustbot label: -S-waiting-on-perf -perf-regression

Instruction count

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

Max RSS (memory usage)

Results (primary 2.6%, secondary 3.1%)

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

mean range count
Regressions ❌
(primary)		 2.6% [1.8%, 3.5%] 2
Regressions ❌
(secondary)		 3.1% [3.1%, 3.1%] 1
Improvements ✅
(primary)		 - - 0
Improvements ✅
(secondary)		 - - 0
All ❌✅ (primary) 2.6% [1.8%, 3.5%] 2

Cycles

Results (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)		 - - 0
Regressions ❌
(secondary)		 2.7% [2.7%, 2.7%] 1
Improvements ✅
(primary)		 - - 0
Improvements ✅
(secondary)		 -2.7% [-3.4%, -2.0%] 2
All ❌✅ (primary) - - 0

Binary size

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

Bootstrap: 470.067s -> 468.269s (-0.38%)
Artifact size: 400.02 MiB -> 400.11 MiB (0.02%)

@rustbot rustbot removed the S-waiting-on-perf Status: Waiting on a perf run to be completed. label Aug 21, 2026
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panstromek marked this pull request as ready for review August 21, 2026 20:31
@rustbot rustbot added the S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. label Aug 21, 2026
@rustbot rustbot removed the S-waiting-on-author Status: This is awaiting some action (such as code changes or more information) from the author. label Aug 21, 2026
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r? @folkertdev

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folkertdev commented Aug 21, 2026

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@bors r+ rollup

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📌 Commit 823b923 has been approved by folkertdev

It is now in the queue for this repository.

@rust-bors rust-bors Bot added S-waiting-on-bors Status: Waiting on bors to run and complete tests. Bors will change the label on completion. and removed S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. labels Aug 21, 2026
JonathanBrouwer added a commit to JonathanBrouwer/rust that referenced this pull request Aug 21, 2026
@JonathanBrouwer
Rollup merge of rust-lang#161476 - panstromek:use-bitset-locals-with-…
c9db83f 
…use-data, r=folkertdev

Use bitset for locals_with_use_data

There seems to be very little reason to use Vec of bools, the whole map allocates space for every element anyway.

Not sure how is impactful this is, I noticed it randomly in the code, but this seems like cleaner way to do it (and more common in the compiler codebase)
@JonathanBrouwer JonathanBrouwer mentioned this pull request Aug 21, 2026
Closed
JonathanBrouwer added a commit to JonathanBrouwer/rust that referenced this pull request Aug 21, 2026
@JonathanBrouwer
Rollup merge of rust-lang#161476 - panstromek:use-bitset-locals-with-…
39478b5 
…use-data, r=folkertdev

Use bitset for locals_with_use_data

There seems to be very little reason to use Vec of bools, the whole map allocates space for every element anyway.

Not sure how is impactful this is, I noticed it randomly in the code, but this seems like cleaner way to do it (and more common in the compiler codebase)
@JonathanBrouwer JonathanBrouwer mentioned this pull request Aug 21, 2026
Closed
JonathanBrouwer added a commit to JonathanBrouwer/rust that referenced this pull request Aug 21, 2026
@JonathanBrouwer
Rollup merge of rust-lang#161476 - panstromek:use-bitset-locals-with-…
a36a1bd 
…use-data, r=folkertdev

Use bitset for locals_with_use_data

There seems to be very little reason to use Vec of bools, the whole map allocates space for every element anyway.

Not sure how is impactful this is, I noticed it randomly in the code, but this seems like cleaner way to do it (and more common in the compiler codebase)
@JonathanBrouwer JonathanBrouwer mentioned this pull request Aug 21, 2026
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