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Unschedule moved locals - #159577

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Unschedule moved locals#159577
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cjgillot:unschedule-moved-locals

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@cjgillot cjgillot commented Jul 19, 2026 •
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Alternative to #159537

This extracts part of the implementation from #125923.

Instead of maintaining a bit-set of locals that are moved from the innermost scope, this PR just removes the locals from the drop schedule.

r? @ghost for perf, and because of a borrowck corner case

@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 Jul 19, 2026
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@rustbot rustbot added the S-waiting-on-perf Status: Waiting on a perf run to be completed. label Jul 19, 2026
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rust-bors Bot pushed a commit that referenced this pull request Jul 19, 2026
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Auto merge of #159577 - cjgillot:unschedule-moved-locals, r=<try>
ab0430c 
Unschedule moved locals
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cjgillot force-pushed the unschedule-moved-locals branch from 53d969a to d9d6173 Compare July 19, 2026 20:40
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☀️ Try build successful (CI)
Build commit: ab0430c (ab0430cfc09675383a04ad2a1b7877ec314aaac9)
Base parent: 9f36de7 (9f36de775bc636c8e88c31a173c2bcb6995956a0)

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Finished benchmarking commit (ab0430c): comparison URL.

Overall result: ❌✅ regressions and improvements - please read:

Benchmarking means the PR may be perf-sensitive. It's automatically marked not fit for rolling up. Overriding is possible but disadvised: it risks changing compiler perf.

Next, please: If you can, justify the regressions found in this try perf run in writing along with @rustbot label: +perf-regression-triaged. If not, fix the regressions and do another perf run. Neutral or positive results will clear the label automatically.

@bors rollup=never rustc-perf
@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)		 0.5% [0.4%, 0.5%] 6
Regressions ❌
(secondary)		 0.3% [0.2%, 0.3%] 2
Improvements ✅
(primary)		 -0.5% [-1.0%, -0.2%] 53
Improvements ✅
(secondary)		 -0.4% [-1.0%, -0.2%] 44
All ❌✅ (primary) -0.4% [-1.0%, 0.5%] 59

Max RSS (memory usage)

Results (primary -0.7%, secondary -0.7%)

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)		 - - 0
Improvements ✅
(primary)		 -0.7% [-0.9%, -0.5%] 3
Improvements ✅
(secondary)		 -0.7% [-0.7%, -0.7%] 1
All ❌✅ (primary) -0.7% [-0.9%, -0.5%] 3

Cycles

Results (primary -2.3%, 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)		 - - 0
Regressions ❌
(secondary)		 - - 0
Improvements ✅
(primary)		 -2.3% [-2.4%, -2.3%] 2
Improvements ✅
(secondary)		 -1.4% [-1.4%, -1.4%] 1
All ❌✅ (primary) -2.3% [-2.4%, -2.3%] 2

Binary size

Results (primary -0.4%, secondary -0.2%)

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

mean range count
Regressions ❌
(primary)		 0.6% [0.6%, 0.6%] 1
Regressions ❌
(secondary)		 - - 0
Improvements ✅
(primary)		 -0.4% [-1.9%, -0.0%] 42
Improvements ✅
(secondary)		 -0.2% [-1.9%, -0.0%] 30
All ❌✅ (primary) -0.4% [-1.9%, 0.6%] 43

Bootstrap: 484.26s -> 485.704s (0.30%)
Artifact size: 391.74 MiB -> 391.76 MiB (0.01%)

@rustbot rustbot added perf-regression Performance regression. and removed S-waiting-on-perf Status: Waiting on a perf run to be completed. labels Jul 19, 2026
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cjgillot commented Jul 20, 2026

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@rustbot rustbot added the S-waiting-on-perf Status: Waiting on a perf run to be completed. label Jul 20, 2026
rust-bors Bot pushed a commit that referenced this pull request Jul 20, 2026
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Auto merge of #159577 - cjgillot:unschedule-moved-locals, r=<try>
563ed1f 
Unschedule moved locals
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☀️ Try build successful (CI)
Build commit: 563ed1f (563ed1fa91907743b81f0cbaac99dc8c8ad29077)
Base parent: 87e5904 (87e5904f5eb6398af6b22eac2802c78934260c48)

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Finished benchmarking commit (563ed1f): comparison URL.

Overall result: ❌✅ regressions and improvements - please read:

Benchmarking means the PR may be perf-sensitive. It's automatically marked not fit for rolling up. Overriding is possible but disadvised: it risks changing compiler perf.

Next, please: If you can, justify the regressions found in this try perf run in writing along with @rustbot label: +perf-regression-triaged. If not, fix the regressions and do another perf run. Neutral or positive results will clear the label automatically.

@bors rollup=never rustc-perf
@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)		 1.3% [0.2%, 11.7%] 65
Regressions ❌
(secondary)		 0.7% [0.1%, 2.0%] 66
Improvements ✅
(primary)		 -0.3% [-0.6%, -0.2%] 10
Improvements ✅
(secondary)		 -0.3% [-0.3%, -0.3%] 2
All ❌✅ (primary) 1.0% [-0.6%, 11.7%] 75

Max RSS (memory usage)

Results (primary 1.7%, secondary 2.4%)

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

mean range count
Regressions ❌
(primary)		 6.9% [6.6%, 7.2%] 2
Regressions ❌
(secondary)		 3.2% [2.1%, 6.0%] 4
Improvements ✅
(primary)		 -1.7% [-3.5%, -0.8%] 3
Improvements ✅
(secondary)		 -0.7% [-0.7%, -0.7%] 1
All ❌✅ (primary) 1.7% [-3.5%, 7.2%] 5

Cycles

Results (primary 10.9%, 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)		 10.9% [1.9%, 23.2%] 6
Regressions ❌
(secondary)		 5.9% [5.9%, 5.9%] 1
Improvements ✅
(primary)		 - - 0
Improvements ✅
(secondary)		 -3.8% [-4.2%, -3.5%] 3
All ❌✅ (primary) 10.9% [1.9%, 23.2%] 6

Binary size

Results (primary -0.4%, secondary -0.2%)

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

mean range count
Regressions ❌
(primary)		 0.6% [0.6%, 0.6%] 1
Regressions ❌
(secondary)		 - - 0
Improvements ✅
(primary)		 -0.4% [-1.9%, -0.0%] 42
Improvements ✅
(secondary)		 -0.2% [-1.9%, -0.0%] 29
All ❌✅ (primary) -0.4% [-1.9%, 0.6%] 43

Bootstrap: 486.983s -> 486.82s (-0.03%)
Artifact size: 391.82 MiB -> 391.79 MiB (-0.01%)

@rustbot rustbot removed the S-waiting-on-perf Status: Waiting on a perf run to be completed. label Jul 21, 2026
@cjgillot
cjgillot force-pushed the unschedule-moved-locals branch from acb7050 to b5a6304 Compare July 22, 2026 00:41
@rustbot rustbot added A-tidy Area: The tidy tool T-bootstrap Relevant to the bootstrap subteam: Rust's build system (x.py and src/bootstrap) labels Jul 22, 2026
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cjgillot commented Jul 22, 2026

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@rustbot rustbot added the S-waiting-on-perf Status: Waiting on a perf run to be completed. label Jul 22, 2026
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rust-bors Bot pushed a commit that referenced this pull request Jul 22, 2026
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Auto merge of #159577 - cjgillot:unschedule-moved-locals, r=<try>
5c95d39 
Unschedule moved locals
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☀️ Try build successful (CI)
Build commit: 5c95d39 (5c95d397a217a2ad69c501c978c9ec972fb53549)
Base parent: 0e29c21 (0e29c21d93abc9bdc330182be1fbd33cfd5fee68)

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rust-timer commented Jul 22, 2026

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Finished benchmarking commit (5c95d39): comparison URL.

Overall result: ❌✅ regressions and improvements - please read:

Benchmarking means the PR may be perf-sensitive. It's automatically marked not fit for rolling up. Overriding is possible but disadvised: it risks changing compiler perf.

Next, please: If you can, justify the regressions found in this try perf run in writing along with @rustbot label: +perf-regression-triaged. If not, fix the regressions and do another perf run. Neutral or positive results will clear the label automatically.

@bors rollup=never rustc-perf
@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)		 0.9% [0.1%, 6.6%] 48
Regressions ❌
(secondary)		 0.7% [0.1%, 1.8%] 36
Improvements ✅
(primary)		 -0.4% [-0.6%, -0.2%] 12
Improvements ✅
(secondary)		 -0.3% [-0.4%, -0.2%] 4
All ❌✅ (primary) 0.6% [-0.6%, 6.6%] 60

Max RSS (memory usage)

Results (primary 1.7%, secondary 1.7%)

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

mean range count
Regressions ❌
(primary)		 2.8% [0.4%, 4.7%] 6
Regressions ❌
(secondary)		 3.2% [1.4%, 6.6%] 9
Improvements ✅
(primary)		 -1.6% [-2.5%, -0.7%] 2
Improvements ✅
(secondary)		 -2.9% [-5.1%, -0.8%] 3
All ❌✅ (primary) 1.7% [-2.5%, 4.7%] 8

Cycles

Results (primary 4.9%, secondary 2.4%)

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

mean range count
Regressions ❌
(primary)		 4.9% [1.2%, 9.9%] 7
Regressions ❌
(secondary)		 2.4% [2.4%, 2.4%] 1
Improvements ✅
(primary)		 - - 0
Improvements ✅
(secondary)		 - - 0
All ❌✅ (primary) 4.9% [1.2%, 9.9%] 7

Binary size

Results (primary -0.4%, secondary -0.2%)

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

mean range count
Regressions ❌
(primary)		 0.6% [0.6%, 0.6%] 1
Regressions ❌
(secondary)		 - - 0
Improvements ✅
(primary)		 -0.4% [-1.9%, -0.0%] 42
Improvements ✅
(secondary)		 -0.2% [-1.9%, -0.0%] 29
All ❌✅ (primary) -0.4% [-1.9%, 0.6%] 43

Bootstrap: 495.463s -> 486.653s (-1.78%)
Artifact size: 387.85 MiB -> 387.83 MiB (-0.00%)

@rustbot rustbot removed the S-waiting-on-perf Status: Waiting on a perf run to be completed. label Jul 22, 2026
@cjgillot
cjgillot force-pushed the unschedule-moved-locals branch 2 times, most recently from c8d01f6 to e226832 Compare August 2, 2026 16:17
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cjgillot commented Aug 2, 2026

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Re-running perf now that #160193 merged.
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@rustbot rustbot added the S-waiting-on-perf Status: Waiting on a perf run to be completed. label Aug 2, 2026
rust-bors Bot pushed a commit that referenced this pull request Aug 2, 2026
@bors
Auto merge of #159577 - cjgillot:unschedule-moved-locals, r=<try>
d28e1ec 
Unschedule moved locals
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☀️ Try build successful (CI)
Build commit: d28e1ec (d28e1ec2b81d75ad63c3cf87781d7c18de255b0c)
Base parent: b04d3c8 (b04d3c8c22822b7f10dab5a563b4e2afff1861c1)

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rust-timer commented Aug 2, 2026

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Finished benchmarking commit (d28e1ec): comparison URL.

Overall result: ❌✅ regressions and improvements - please read:

Benchmarking means the PR may be perf-sensitive. It's automatically marked not fit for rolling up. Overriding is possible but disadvised: it risks changing compiler perf.

Next, please: If you can, justify the regressions found in this try perf run in writing along with @rustbot label: +perf-regression-triaged. If not, fix the regressions and do another perf run. Neutral or positive results will clear the label automatically.

@bors rollup=never rustc-perf
@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)		 0.6% [0.2%, 1.8%] 40
Regressions ❌
(secondary)		 0.6% [0.1%, 1.6%] 33
Improvements ✅
(primary)		 -0.4% [-0.6%, -0.2%] 10
Improvements ✅
(secondary)		 - - 0
All ❌✅ (primary) 0.4% [-0.6%, 1.8%] 50

Max RSS (memory usage)

Results (primary 1.0%, secondary 0.4%)

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

mean range count
Regressions ❌
(primary)		 1.4% [0.4%, 2.4%] 4
Regressions ❌
(secondary)		 1.8% [0.4%, 6.8%] 9
Improvements ✅
(primary)		 -0.6% [-0.6%, -0.6%] 1
Improvements ✅
(secondary)		 -3.6% [-4.4%, -2.7%] 3
All ❌✅ (primary) 1.0% [-0.6%, 2.4%] 5

Cycles

Results (primary -1.2%, 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)		 - - 0
Regressions ❌
(secondary)		 2.2% [0.5%, 3.4%] 3
Improvements ✅
(primary)		 -1.2% [-3.0%, -0.5%] 13
Improvements ✅
(secondary)		 -2.5% [-15.5%, -0.4%] 18
All ❌✅ (primary) -1.2% [-3.0%, -0.5%] 13

Binary size

Results (primary -0.3%, secondary -0.2%)

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

mean range count
Regressions ❌
(primary)		 0.1% [0.1%, 0.6%] 11
Regressions ❌
(secondary)		 0.1% [0.1%, 0.1%] 1
Improvements ✅
(primary)		 -0.3% [-1.9%, -0.0%] 56
Improvements ✅
(secondary)		 -0.2% [-1.9%, -0.0%] 31
All ❌✅ (primary) -0.3% [-1.9%, 0.6%] 67

Bootstrap: 491.057s -> 490.667s (-0.08%)
Artifact size: 390.41 MiB -> 391.17 MiB (0.20%)

@rustbot rustbot removed the S-waiting-on-perf Status: Waiting on a perf run to be completed. label Aug 2, 2026
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cjgillot and others added 8 commits August 3, 2026 01:51
@cjgillot
Mark locals used to construct Aggregates as moved.
2bc6011 
And some more cases along the way.

We have a specific optimization to avoid generating useless drops, use it.
In particular, aggregate construction are very similar to function calls
for which this is designed.
@cjgillot
Add test.
90faaf7
@cjgillot
Use a GrowableBitSet for moved_locals.
949deb7
@cjgillot
Review nits.
4a13b8f
@cjgillot @dianne
Make test comment more precise.
4ad2c3f 
Co-authored-by: dianne <diannes.gm@gmail.com>
@cjgillot
Unschedule drops instead of setting a bitset.
b2abfec
@cjgillot
Split critical edges before borrowck.
1e1bce0
@cjgillot
Only split unwind edges.
36708a4
@cjgillot
cjgillot force-pushed the unschedule-moved-locals branch from e226832 to 36708a4 Compare August 3, 2026 03:12
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rust-bors Bot commented Aug 9, 2026

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☔ The latest upstream changes (presumably #160814) made this pull request unmergeable. Please resolve the merge conflicts by rebasing.

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