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Add 2025-10-13 triage #2280

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# 2025-10-13 Triage Log

This week saw small wins across the board from some microoptimizations of the incremental query
system ([#147423](https://github.com/rust-lang/rust/pull/147423)). There have also been a couple of
regressions. [#142390](https://github.com/rust-lang/rust/pull/142390) introduced regressions of `check`
builds across the board. The largest regression (18%) is from an incremental opt build of a secondary
artificial stress test, so we deemed it acceptable.
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Also incremental opt is not a default config IIRC

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What do you mean by default config?

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@lqd lqd Oct 13, 2025 •
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Something that cargo does out of the box. You need to opt into incremental for release builds IIRC, since codegen is worse. It’s not a configuration that people would usually use.

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Yes, and I think the same is true for Check Full and Debug Full because Check/Debug are incremental by default. I've previously wondered if we should account for this somehow, possibly even removing some of the combinations.

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@Kobzol Kobzol Oct 14, 2025 •
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I do personally use incremental release builds from time to time, and I do use them almost all the time when building the compiler itself. Non-incremental check/debug is also very common in CI pipelines, because there incremental builds are disabled in 99.9% of cases, and most people just do cargo check/build to have the build finish faster.


Triage done by **@kobzol**.
Revision range: [1a3cdd34..956f47c3](https://perf.rust-lang.org/?start=1a3cdd34629306fa67624eaa60d73687e7fcf855&end=956f47c32f1bd97b22cd702d7ccf78f0f0d42c34&absolute=false&stat=instructions%3Au)

**Summary**:

| (instructions:u) | mean | range | count |
|:----------------------------------:|:-----:|:--------------:|:-----:|
| Regressions ❌ <br /> (primary) | 0.7% | [0.1%, 2.0%] | 65 |
| Regressions ❌ <br /> (secondary) | 0.8% | [0.1%, 18.6%] | 65 |
| Improvements ✅ <br /> (primary) | -0.6% | [-1.6%, -0.1%] | 119 |
| Improvements ✅ <br /> (secondary) | -0.4% | [-1.6%, -0.1%] | 76 |
| All ❌✅ (primary) | -0.1% | [-1.6%, 2.0%] | 184 |


2 Regressions, 7 Improvements, 3 Mixed; 3 of them in rollups
35 artifact comparisons made in total

#### Regressions

Rollup of 12 pull requests [#147512](https://github.com/rust-lang/rust/pull/147512) [(Comparison Link)](https://perf.rust-lang.org/compare.html?start=bd3487101ff9397ca8a54dd83aa360d93342b82e&end=acf243778e6c54cb7d54bee4be88e510e4be123e&stat=instructions:u)

| (instructions:u) | mean | range | count |
|:----------------------------------:|:----:|:------------:|:-----:|
| Regressions ❌ <br /> (primary) | - | - | 0 |
| Regressions ❌ <br /> (secondary) | 0.4% | [0.0%, 0.8%] | 10 |
| Improvements ✅ <br /> (primary) | - | - | 0 |
| Improvements ✅ <br /> (secondary) | - | - | 0 |
| All ❌✅ (primary) | - | - | 0 |

- Noise, the secondary benchmarks have rebounded in [#147519](https://github.com/rust-lang/rust/pull/147519).
- Marked as triaged.

Fix normalization overflow ICEs in monomorphization [#146096](https://github.com/rust-lang/rust/pull/146096) [(Comparison Link)](https://perf.rust-lang.org/compare.html?start=2300c2aef7dbc2a7bbbeaa9894d07d459abd9bc6&end=36e4f5d1fe1d63953a5bf1758ce2b64172623e2e&stat=instructions:u)

| (instructions:u) | mean | range | count |
|:----------------------------------:|:----:|:-------------:|:-----:|
| Regressions ❌ <br /> (primary) | 0.4% | [0.2%, 0.6%] | 5 |
| Regressions ❌ <br /> (secondary) | 9.7% | [0.7%, 18.7%] | 2 |
| Improvements ✅ <br /> (primary) | - | - | 0 |
| Improvements ✅ <br /> (secondary) | - | - | 0 |
| All ❌✅ (primary) | 0.4% | [0.2%, 0.6%] | 5 |

- The perf. hit was expected and deemed worth it, as this PR fixes a couple of issues.
- Apart from some tiny regressions, the single large regression is in a secondary stress test, and also in full incremental opt build.
- Marked as triaged.

#### Improvements

Rollup of 7 pull requests [#147449](https://github.com/rust-lang/rust/pull/147449) [(Comparison Link)](https://perf.rust-lang.org/compare.html?start=fed46ffd5059e11669df1bd9406b02914c3fb73f&end=d62f33a7c684473bf6efa2f3ff57093bb8986141&stat=instructions:u)

| (instructions:u) | mean | range | count |
|:----------------------------------:|:-----:|:--------------:|:-----:|
| Regressions ❌ <br /> (primary) | - | - | 0 |
| Regressions ❌ <br /> (secondary) | - | - | 0 |
| Improvements ✅ <br /> (primary) | -0.2% | [-0.3%, -0.1%] | 8 |
| Improvements ✅ <br /> (secondary) | -0.5% | [-0.5%, -0.5%] | 1 |
| All ❌✅ (primary) | -0.2% | [-0.3%, -0.1%] | 8 |


`DepNodeColor` tweaks [#147423](https://github.com/rust-lang/rust/pull/147423) [(Comparison Link)](https://perf.rust-lang.org/compare.html?start=4fd31815524baba0bf368f151f757101f432e3de&end=5767910cbcc9d199bf261a468574d45aa3857599&stat=instructions:u)

| (instructions:u) | mean | range | count |
|:----------------------------------:|:-----:|:--------------:|:-----:|
| Regressions ❌ <br /> (primary) | - | - | 0 |
| Regressions ❌ <br /> (secondary) | - | - | 0 |
| Improvements ✅ <br /> (primary) | -0.6% | [-1.5%, -0.2%] | 98 |
| Improvements ✅ <br /> (secondary) | -0.6% | [-1.2%, -0.1%] | 47 |
| All ❌✅ (primary) | -0.6% | [-1.5%, -0.2%] | 98 |


[rustdoc] a small performance improvement: only allocate new string if there are DOS backlines in highlight.rs [#147443](https://github.com/rust-lang/rust/pull/147443) [(Comparison Link)](https://perf.rust-lang.org/compare.html?start=82224f6891c7e7aa0c6c865aa825100b3ea2d0fb&end=910617d84d611e9ba508fd57a058c59b8a767697&stat=instructions:u)

| (instructions:u) | mean | range | count |
|:----------------------------------:|:-----:|:--------------:|:-----:|
| Regressions ❌ <br /> (primary) | - | - | 0 |
| Regressions ❌ <br /> (secondary) | - | - | 0 |
| Improvements ✅ <br /> (primary) | -0.2% | [-0.3%, -0.1%] | 4 |
| Improvements ✅ <br /> (secondary) | -0.2% | [-0.5%, -0.0%] | 5 |
| All ❌✅ (primary) | -0.2% | [-0.3%, -0.1%] | 4 |


Refactor AddCallGuards in two loops. [#147477](https://github.com/rust-lang/rust/pull/147477) [(Comparison Link)](https://perf.rust-lang.org/compare.html?start=b6f0945e4681bc4d2faa7c22c5f61dc36abf7dd2&end=61efd190243db101d1e47c82c7ec543565c25f62&stat=instructions:u)

| (instructions:u) | mean | range | count |
|:----------------------------------:|:-----:|:--------------:|:-----:|
| Regressions ❌ <br /> (primary) | - | - | 0 |
| Regressions ❌ <br /> (secondary) | - | - | 0 |
| Improvements ✅ <br /> (primary) | -0.2% | [-0.3%, -0.1%] | 8 |
| Improvements ✅ <br /> (secondary) | -0.3% | [-0.6%, -0.1%] | 9 |
| All ❌✅ (primary) | -0.2% | [-0.3%, -0.1%] | 8 |


Move more code to `RawVec::finish_grow` [#147124](https://github.com/rust-lang/rust/pull/147124) [(Comparison Link)](https://perf.rust-lang.org/compare.html?start=360a3a4e65cb70ea6e9da69cbb15f460dee516fd&end=be0ade2b602bdfe37a3cc259fcc79e8624dcba94&stat=instructions:u)

| (instructions:u) | mean | range | count |
|:----------------------------------:|:-----:|:--------------:|:-----:|
| Regressions ❌ <br /> (primary) | - | - | 0 |
| Regressions ❌ <br /> (secondary) | - | - | 0 |
| Improvements ✅ <br /> (primary) | -0.2% | [-0.4%, -0.1%] | 5 |
| Improvements ✅ <br /> (secondary) | -0.1% | [-0.2%, -0.0%] | 7 |
| All ❌✅ (primary) | -0.2% | [-0.4%, -0.1%] | 5 |


Rollup of 8 pull requests [#147603](https://github.com/rust-lang/rust/pull/147603) [(Comparison Link)](https://perf.rust-lang.org/compare.html?start=3be68033b67dfc2aa3ae4cfe735aa5805aebae43&end=89276493d3c3f85691e76b27a9dde7ec82e79cdb&stat=instructions:u)

| (instructions:u) | mean | range | count |
|:----------------------------------:|:-----:|:--------------:|:-----:|
| Regressions ❌ <br /> (primary) | - | - | 0 |
| Regressions ❌ <br /> (secondary) | 0.0% | [0.0%, 0.0%] | 1 |
| Improvements ✅ <br /> (primary) | -0.2% | [-0.2%, -0.1%] | 3 |
| Improvements ✅ <br /> (secondary) | -0.1% | [-0.1%, -0.0%] | 13 |
| All ❌✅ (primary) | -0.2% | [-0.2%, -0.1%] | 3 |


Split overlapping_{inherent,trait}_impls [#147502](https://github.com/rust-lang/rust/pull/147502) [(Comparison Link)](https://perf.rust-lang.org/compare.html?start=35456985fab3419baf4bf111b8bbbd5e8565615d&end=956f47c32f1bd97b22cd702d7ccf78f0f0d42c34&stat=instructions:u)

| (instructions:u) | mean | range | count |
|:----------------------------------:|:-----:|:--------------:|:-----:|
| Regressions ❌ <br /> (primary) | - | - | 0 |
| Regressions ❌ <br /> (secondary) | - | - | 0 |
| Improvements ✅ <br /> (primary) | -0.2% | [-0.4%, -0.1%] | 15 |
| Improvements ✅ <br /> (secondary) | -0.2% | [-0.2%, -0.1%] | 4 |
| All ❌✅ (primary) | -0.2% | [-0.4%, -0.1%] | 15 |


#### Mixed

Prevent downstream `impl DerefMut for Pin<LocalType>` [#145608](https://github.com/rust-lang/rust/pull/145608) [(Comparison Link)](https://perf.rust-lang.org/compare.html?start=4a54b26d30dac43778afb0e503524b763fce0eee&end=fed46ffd5059e11669df1bd9406b02914c3fb73f&stat=instructions:u)

| (instructions:u) | mean | range | count |
|:----------------------------------:|:-----:|:--------------:|:-----:|
| Regressions ❌ <br /> (primary) | 0.3% | [0.3%, 0.3%] | 2 |
| Regressions ❌ <br /> (secondary) | - | - | 0 |
| Improvements ✅ <br /> (primary) | - | - | 0 |
| Improvements ✅ <br /> (secondary) | -0.0% | [-0.0%, -0.0%] | 1 |
| All ❌✅ (primary) | 0.3% | [0.3%, 0.3%] | 2 |

- Tiny regression on hyper, otherwise netural. This PR fixes soundness anyway.
- Marked as triaged.

Perform InstSimplify before ReferencePropagation. [#147483](https://github.com/rust-lang/rust/pull/147483) [(Comparison Link)](https://perf.rust-lang.org/compare.html?start=4b57d8154a6a74d2514cd3a674c1f29a588f224a&end=0b278a539440be291466ea463a9b6310eaf4d7bb&stat=instructions:u)

| (instructions:u) | mean | range | count |
|:----------------------------------:|:-----:|:--------------:|:-----:|
| Regressions ❌ <br /> (primary) | - | - | 0 |
| Regressions ❌ <br /> (secondary) | 0.2% | [0.1%, 0.7%] | 6 |
| Improvements ✅ <br /> (primary) | -0.3% | [-0.5%, -0.1%] | 6 |
| Improvements ✅ <br /> (secondary) | -0.3% | [-0.6%, -0.1%] | 6 |
| All ❌✅ (primary) | -0.3% | [-0.5%, -0.1%] | 6 |

- Some tiny wins on primary benchmarks, but overall it's a wash.
- Marked as triaged.

Perform unused assignment and unused variables lints on MIR. [#142390](https://github.com/rust-lang/rust/pull/142390) [(Comparison Link)](https://perf.rust-lang.org/compare.html?start=89276493d3c3f85691e76b27a9dde7ec82e79cdb&end=ff6dc928c5e33ce8e65c6911a790b9efcb5ef53a&stat=instructions:u)

| (instructions:u) | mean | range | count |
|:----------------------------------:|:-----:|:--------------:|:-----:|
| Regressions ❌ <br /> (primary) | 0.6% | [0.1%, 2.0%] | 75 |
| Regressions ❌ <br /> (secondary) | 0.7% | [0.0%, 3.7%] | 76 |
| Improvements ✅ <br /> (primary) | -0.3% | [-0.3%, -0.3%] | 1 |
| Improvements ✅ <br /> (secondary) | -0.4% | [-0.5%, -0.4%] | 6 |
| All ❌✅ (primary) | 0.6% | [-0.3%, 2.0%] | 76 |

- The regressions on the check builds are real, but they mostly didn't carry over to debug and opt builds. This is a big compiler change that took years to land, so I think that we just eat the cost.
- Marked as triaged.
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