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DestinationPropagation: avoid creating overlapping assignments. #146516

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Merged
merged 4 commits into from
Sep 16, 2025
Merged

DestinationPropagation: avoid creating overlapping assignments. #146516

merged 4 commits into from
Sep 16, 2025

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cjgillot
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@cjgillot cjgillot commented Sep 13, 2025 •
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r? @Amanieu

Fixes #146383

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rustbot commented Sep 13, 2025

Some changes occurred to MIR optimizations

cc @rust-lang/wg-mir-opt

@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 13, 2025
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Amanieu
Amanieu reviewed Sep 13, 2025
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compiler/rustc_mir_transform/src/dest_prop.rs Outdated
DefUse::Def | DefUse::PartialWrite => {
if let Some(relevant) = relevant.shrink[place.local] {
values.insert(relevant, twostep);
let is_simple_assignment =
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This could use an explanatory comment: overlaps aren't allowed so we can only treat the source and destination of an assignment as disjoint if they are "simple" and in a form we can later eliminate at the end of this pass.

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@cjgillot cjgillot added the A-mir-opt Area: MIR optimizations label Sep 14, 2025
Amanieu
Amanieu reviewed Sep 15, 2025
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Amanieu commented Sep 16, 2025

@bors r+

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bors commented Sep 16, 2025

📌 Commit d58061e has been approved by Amanieu

It is now in the queue for this repository.

@bors bors 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 16, 2025
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bors commented Sep 16, 2025

⌛ Testing commit d58061e with merge eec6bd9...

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bors commented Sep 16, 2025

☀️ Test successful - checks-actions
Approved by: Amanieu
Pushing eec6bd9 to master...

@bors bors added the merged-by-bors This PR was explicitly merged by bors. label Sep 16, 2025
@bors bors merged commit eec6bd9 into rust-lang:master Sep 16, 2025
11 checks passed
@rustbot rustbot added this to the 1.92.0 milestone Sep 16, 2025
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What is this? This is an experimental post-merge analysis report that shows differences in test outcomes between the merged PR and its parent PR.

Comparing 8a1b399 (parent) -> eec6bd9 (this PR)

Test differences

Show 4 test diffs

Stage 1

  • [mir-opt] tests/mir-opt/dest-prop/aggregate.rs: [missing] -> pass (J0)

Stage 2

  • [mir-opt] tests/mir-opt/dest-prop/aggregate.rs: [missing] -> pass (J1)

Additionally, 2 doctest diffs were found. These are ignored, as they are noisy.

Job group index

Test dashboard

Run

cargo run --manifest-path src/ci/citool/Cargo.toml -- \
    test-dashboard eec6bd9d69832f57341c6de6a93fa7b9f47e2111 --output-dir test-dashboard

And then open test-dashboard/index.html in your browser to see an overview of all executed tests.

Job duration changes

  1. dist-aarch64-apple: 5966.0s -> 6802.3s (14.0%)
  2. aarch64-msvc-2: 4819.0s -> 5467.4s (13.5%)
  3. dist-x86_64-apple: 7952.2s -> 6905.8s (-13.2%)
  4. dist-apple-various: 3766.4s -> 4218.4s (12.0%)
  5. dist-riscv64-linux: 5187.1s -> 4735.6s (-8.7%)
  6. aarch64-gnu-debug: 3695.9s -> 3935.2s (6.5%)
  7. dist-armv7-linux: 5281.0s -> 4942.0s (-6.4%)
  8. dist-s390x-linux: 4922.7s -> 5228.7s (6.2%)
  9. x86_64-msvc-ext1: 7832.0s -> 7369.9s (-5.9%)
  10. dist-x86_64-solaris: 5139.7s -> 5424.4s (5.5%)
How to interpret the job duration changes?

Job durations can vary a lot, based on the actual runner instance
that executed the job, system noise, invalidated caches, etc. The table above is provided
mostly for t-infra members, for simpler debugging of potential CI slow-downs.

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Finished benchmarking commit (eec6bd9): comparison URL.

Overall result: ✅ improvements - no action needed

@rustbot label: -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
Improvements ✅
(secondary)		 -0.6% [-0.7%, -0.4%] 5
All ❌✅ (primary) - - 0

Max RSS (memory usage)

This benchmark run did not return any relevant results for this metric.

Cycles

This benchmark run did not return any relevant results for this metric.

Binary size

This benchmark run did not return any relevant results for this metric.

Bootstrap: 473.032s -> 473.048s (0.00%)
Artifact size: 390.60 MiB -> 390.57 MiB (-0.01%)

@cjgillot cjgillot deleted the dest-prop-aggregate branch September 16, 2025 21:56
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A-mir-opt Area: MIR optimizations merged-by-bors This PR was explicitly merged by bors. S-waiting-on-bors Status: Waiting on bors to run and complete tests. Bors will change the label on completion. T-compiler Relevant to the compiler team, which will review and decide on the PR/issue.

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Successfully merging this pull request may close these issues.

Miscompile in DestinationPropagation?

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@cjgillot @rustbot @rust-log-analyzer @Amanieu @bors @rust-timer