| # 2020-12-08 Triage Log |
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| Quiet week. |
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| Triage done by **@simulacrum**. |
| Revision range: [c7cff213e937c1bb301be807ce04fcf6092b9163..4fd4a98d4788bc987d7f7add9df5f5ead6a1c15e](https://perf.rust-lang.org/?start=c7cff213e937c1bb301be807ce04fcf6092b9163&end=4fd4a98d4788bc987d7f7add9df5f5ead6a1c15e&absolute=false&stat=instructions%3Au) |
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| 0 Regressions, 2 Improvements, 1 Mixed |
| 0 of them in rollups |
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| #### Regressions |
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| #### Improvements |
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| [#79594](https://github.com/rust-lang/rust/issues/79594) |
| - Moderate improvement in [instruction counts](https://perf.rust-lang.org/compare.html?start=c7cff213e937c1bb301be807ce04fcf6092b9163&end=d015f0d92144f0e72735a918aee8510b0fe2cff5&stat=instructions:u) (up to -1.7% on `incr-full` builds of `ctfe-stress-4-debug`) |
| - Likely due to the stress test not reflecting benefits of memoizing CTFE, which |
| this partially removed (due to the addition of heap allocation, which should |
| not be deduplicated). |
| |
| [#79680](https://github.com/rust-lang/rust/issues/79680) |
| - Very large improvement in [instruction counts](https://perf.rust-lang.org/compare.html?start=e6225434fff7d493baac0aa91c57f2da923ea196&end=2218520b8adf8b8e64b817537d9eb0a84840e2f1&stat=instructions:u) (up to -20.6% on `full` builds of `match-stress-enum-check`) |
| - Fixes a regression from last week by adding a `#[inline]` attribute on some |
| hot code. Improvements are likely not significant outside stress tests. |
| |
| #### Mixed |
| |
| [#78373](https://github.com/rust-lang/rust/issues/78373) |
| - Very large improvement in [instruction counts](https://perf.rust-lang.org/compare.html?start=551a2c6cbcf239f662a18233cf647bf67e5a74ed&end=9122b769c8306b1cb3c8d1f96fca3ea3e208e22e&stat=instructions:u) (up to -28.4% on `incr-patched: println` builds of `clap-rs-debug`) |
| - Large regression in [instruction counts](https://perf.rust-lang.org/compare.html?start=551a2c6cbcf239f662a18233cf647bf67e5a74ed&end=9122b769c8306b1cb3c8d1f96fca3ea3e208e22e&stat=instructions:u) (up to 9.9% on `incr-patched: println` builds of `regression-31157-opt`) |
| - Soundness fix ("Don't leak return value after panic in drop") and the perf |
| results are mixed, largest ones mostly in incremental and generally likely |
| just "generating more (necessary) LLVM IR". |
| |
| #### Nags requiring follow up |
| |
| - stdarch expansion causing a 40% libcore compile time regression is still not |
| resolved, and resolution is unclear. It seems likely that this could be one of |
| our key elements for improving std compile times at least, though. |
| - No new nags. |
