2020-09-15 Triage Log

See the README for details on how this log was gathered.

Triage done by @Mark-Simulacrum. Revision range: 35fc8359868e65a0970094f648ba87fce634e8c7..a53f449516f23486d2dfd4e5685d4e869e8591d9

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

Regressions

Removing the def_id field from hot ParamEnv to make it smaller #76244

• A 3% instruction and 25% wall-time regression on some benchmarks.

Improvements

BTreeMap mutable iterators should not take any reference to visited nodes during iteration #73971

• A ~1.4% improvement on token-stream-stress check in instruction counts

make ConstEvaluatable more strict #74595

• Improvement of up to 2% in instruction counts

Nags requiring follow up

• #76244
  • Consider a revert if no comments