# 2020-09-15 Triage Log

See the [README](README.md) for details on how this log was gathered.

Triage done by @Mark-Simulacrum.
Revision range: [35fc8359868e65a0970094f648ba87fce634e8c7..a53f449516f23486d2dfd4e5685d4e869e8591d9](https://perf.rust-lang.org/index.html?start=35fc8359868e65a0970094f648ba87fce634e8c7&end=a53f449516f23486d2dfd4e5685d4e869e8591d9&absolute=false&stat=instructions%3Au)

1 Regressions, 2 Improvements, 0 of them in rollups.

#### Regressions

[Removing the `def_id` field from hot `ParamEnv` to make it smaller #76244](https://github.com/rust-lang/rust/pull/76244)
- A 3% instruction and [25% wall-time](https://perf.rust-lang.org/compare.html?start=a055c5a1bd95e029e9b31891db63b6dc8258b472&end=7402a394471a6738a40fea7d4f1891666e5a80c5&stat=task-clock) regression on some benchmarks.

#### Improvements

[BTreeMap mutable iterators should not take any reference to visited nodes during iteration #73971](https://github.com/rust-lang/rust/pull/73971)
- A ~1.4% improvement on token-stream-stress check in [instruction counts](https://perf.rust-lang.org/compare.html?start=b4bdc07ff5a70175dbcdff7331c557245ddb012f&end=d92155bf6ae0b7d79fc83cbeeb0cc0c765353471)

[make `ConstEvaluatable` more strict #74595](https://github.com/rust-lang/rust/pull/74595)
- Improvement of up to 2% in [instruction counts](https://perf.rust-lang.org/compare.html?start=d92155bf6ae0b7d79fc83cbeeb0cc0c765353471&end=e2be5f568d1f60365b825530f5b5cb722460591b)

#### Nags requiring follow up

* [#76244](https://github.com/rust-lang/rust/pull/76244#issuecomment-694459840)
    * Consider a revert if no comments
