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Use DenseBit for drop_live_at in liveness tracing - #162488

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Use DenseBit for drop_live_at in liveness tracing#162488
Kobzol wants to merge 1 commit into
rust-lang:mainfrom
Kobzol:borrowck-densebit

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@Kobzol

@Kobzol Kobzol commented Sep 8, 2026

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I noticed that drop_live_at only ever gets point, and never range, inserts, so I switched it over to DenseBitSet. This provides some nice wins on serde.

However, the add_drop_live_facts_for function expects to receive an IntervalSet. I first tried to switch the type of LiveRegions::AtPoints from SparseIntervalMatrix to SparseBitMatrix, but that had regressions.

So in this PR, I simply reconstruct an IntervalSet from a DenseBitSet. Not super pretty, but perf. looks reasonable.

Let me know if this makes sense or not! :)

r? jackh726

@rustbot rustbot added S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. T-compiler Relevant to the compiler team, which will review and decide on the PR/issue. labels Sep 8, 2026
jackh726
jackh726 reviewed Sep 8, 2026
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Comment thread compiler/rustc_borrowck/src/type_check/liveness/trace.rs
&self.drop_locations,
&self.drop_live_at,
);
let mut set: IntervalSet<PointIndex> =

@jackh726 jackh726 Sep 8, 2026 •
edited by rustbot
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@jackh726

jackh726 commented Sep 8, 2026

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Cool :) r=me with comment added

@jackh726

jackh726 commented Sep 8, 2026

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@bors rollup=never

@Kobzol

Kobzol commented Sep 8, 2026

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Cool, added a comment. Thank you!

@bors r=jackh726

And for good measure:
@bors try @rust-timer queue

@rust-timer

rust-timer commented Sep 8, 2026

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Awaiting bors try build completion.

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

@rust-bors

rust-bors Bot commented Sep 8, 2026

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📌 Commit 855183d has been approved by jackh726

It is now in the queue for this repository.

🌲 The tree is currently closed for pull requests below priority 5. This pull request will be tested once the tree is reopened.

Reason for tree closure: spurious failures

@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 Sep 8, 2026
@rustbot rustbot added the S-waiting-on-perf Status: Waiting on a perf run to be completed. label Sep 8, 2026
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rust-bors Bot pushed a commit that referenced this pull request Sep 8, 2026
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Auto merge of #162488 - Kobzol:borrowck-densebit, r=<try>
0f7d1ae 
Use `DenseBit` for `drop_live_at` in liveness tracing
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@rust-bors rust-bors Bot added S-waiting-on-author Status: This is awaiting some action (such as code changes or more information) from the author. and removed S-waiting-on-bors Status: Waiting on bors to run and complete tests. Bors will change the label on completion. labels Sep 8, 2026
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rust-bors Bot commented Sep 8, 2026

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⚠️ A new commit 1b1b92ed33d64bc3d722be6f13f9fc6a23faa858 was pushed.

This pull request was unapproved.

@Kobzol

Kobzol commented Sep 8, 2026

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Impressive, I managed to make the code stop compiling by adding a comment 🤦 Enough GitHub for today. Second try:

@bors r=jackh726
@bors try

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rust-bors Bot commented Sep 8, 2026

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📌 Commit 1b1b92e has been approved by jackh726

It is now in the queue for this repository.

🌲 The tree is currently closed for pull requests below priority 5. This pull request will be tested once the tree is reopened.

Reason for tree closure: spurious failures

@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-author Status: This is awaiting some action (such as code changes or more information) from the author. labels Sep 8, 2026
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rust-bors Bot pushed a commit that referenced this pull request Sep 8, 2026
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Auto merge of #162488 - Kobzol:borrowck-densebit, r=<try>
57ac888 
Use `DenseBit` for `drop_live_at` in liveness tracing
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rust-bors Bot commented Sep 8, 2026

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☀️ Try build successful (CI)
Build commit: 57ac888 (57ac8880a9ace2c2311fd96b2b77f5fad68483b4)
Base parent: 745de6e (745de6eca673de5329ec68f2689629a5ca45ab35)

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rust-timer commented Sep 8, 2026

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Queued 57ac888 with parent 745de6e, future comparison URL.
There is currently 1 preceding artifact in the queue.
It will probably take at least ~1.4 hours until the benchmark run finishes.

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