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Skip move checks when the size limit is zero - #164332

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charliermarsh:charlie/skip-disabled-move-checks
Oct 15, 2026
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Skip move checks when the size limit is zero#164332
rust-bors[bot] merged 1 commit into
rust-lang:mainfrom
charliermarsh:charlie/skip-disabled-move-checks

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@charliermarsh

@charliermarsh charliermarsh commented Oct 14, 2026

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Summary

When the move-size limit is zero (i.e., the default), the individual large-assignment checks already return without doing anything. But we still traverse the reachable MIR blocks and monomorphize callee types before reaching those checks. This PR instead returns early from check_moves.

@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 Oct 14, 2026
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r? @TaKO8Ki

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@Kobzol

Kobzol commented Oct 14, 2026

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@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 Oct 14, 2026
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rust-bors Bot pushed a commit that referenced this pull request Oct 14, 2026
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Auto merge of #164332 - charliermarsh:charlie/skip-disabled-move-chec…
b5c78cd 
…ks, r=<try>

Skip move checks when the size limit is zero
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☀️ Try build successful (CI)
Build commit: b5c78cd (b5c78cd49f88d89a5c2aeb383c2d273a22a00cf1)
Base parent: 7df8138 (7df81381d027710708209f36b98d11b1c88f8d2e)

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rust-timer commented Oct 15, 2026

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Finished benchmarking commit (b5c78cd): comparison URL.

Overall result: ✅ improvements - no action needed

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

@bors rollup=iffy 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
Regressions ❌
(secondary)		 - - 0
Improvements ✅
(primary)		 -0.8% [-0.8%, -0.8%] 1
Improvements ✅
(secondary)		 -0.3% [-0.6%, -0.2%] 6
All ❌✅ (primary) -0.8% [-0.8%, -0.8%] 1

Max RSS (memory usage)

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

Cycles

Results (primary 2.4%, secondary 4.2%)

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

mean range count
Regressions ❌
(primary)		 2.4% [2.4%, 2.4%] 1
Regressions ❌
(secondary)		 4.2% [4.2%, 4.2%] 1
Improvements ✅
(primary)		 - - 0
Improvements ✅
(secondary)		 - - 0
All ❌✅ (primary) 2.4% [2.4%, 2.4%] 1

Binary size

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

Bootstrap: 489.902s -> 487.199s (-0.55%)
Artifact size: 407.05 MiB -> 406.95 MiB (-0.02%)

@rustbot rustbot removed the S-waiting-on-perf Status: Waiting on a perf run to be completed. label Oct 15, 2026
@TaKO8Ki

TaKO8Ki commented Oct 15, 2026 •
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Thank you! @bors r+ rollup

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📌 Commit fd1029d has been approved by TaKO8Ki

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 Oct 15, 2026
@JonathanBrouwer JonathanBrouwer mentioned this pull request Oct 15, 2026
Merged
rust-bors Bot pushed a commit that referenced this pull request Oct 15, 2026
@bors
Auto merge of #164367 - JonathanBrouwer:rollup-pmUrlQY, r=JonathanBro…
56df459 
…uwer

Rollup of 2 pull requests

Successful merges:

 - #164332 (Skip move checks when the size limit is zero)
 - #164351 (Print exit code if rustc fails in compiletest)
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rust-bors Bot merged commit 3a03efb into rust-lang:main Oct 15, 2026
15 checks passed
@rustbot rustbot added this to the 1.101.0 milestone Oct 15, 2026
rust-bors Bot pushed a commit that referenced this pull request Oct 15, 2026
@bors
Unrolled build for #164332 in rollup 164367
b6d908e 
Rollup merge of #164332 - charliermarsh:charlie/skip-disabled-move-checks, r=TaKO8Ki

Skip move checks when the size limit is zero

## Summary

When the move-size limit is zero (i.e., the default), the individual large-assignment checks already return without doing anything. But we still traverse the reachable MIR blocks and monomorphize callee types before reaching those checks. This PR instead returns early from `check_moves`.
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@TaKO8Ki TaKO8Ki TaKO8Ki approved these changes

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@TaKO8Ki TaKO8Ki

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@charliermarsh @rustbot @Kobzol @rust-timer @TaKO8Ki