Add triage for this week

Author: Mark-Simulacrum

triage/2021-06-08.md

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+# 2021-06-08 Triage Log
+
+Some good improvements, and a few regressions. No large changes.
+
+Triage done by **@simulacrum**.
+Revision range: [1160cf864f2a0014e3442367e1b96496bfbeadf4..a50d72158e08e02cfc051b863017bdbd2c45b637](https://perf.rust-lang.org/?start=1160cf864f2a0014e3442367e1b96496bfbeadf4&end=a50d72158e08e02cfc051b863017bdbd2c45b637&absolute=false&stat=instructions%3Au)
+
+3 Regressions, 3 Improvements, 1 Mixed
+1 of them in rollups
+
+#### Regressions
+
+Always go through the expn_that_defined query. [#86002](https://github.com/rust-lang/rust/issues/86002)
+- Moderate regression in [instruction counts](https://perf.rust-lang.org/compare.html?start=ac3e680193a3e11e60b07840ffb1db12793de110&end=6c2dd251bbff03c7a3092d43fb5b637eca0810e3&stat=instructions:u) (up to 1.6% on `incr-patched: println` builds of `webrender-check`)
+- Necessary for correctness, regresions largely limited to incremental.
+
+Add variance-related information to lifetime error messages [#85343](https://github.com/rust-lang/rust/issues/85343)
+- Moderate regression in [instruction counts](https://perf.rust-lang.org/compare.html?start=5b638c1d3751b7ab31cac9739add516bdf39e10a&end=35fff69d043b1c0f5c29894e7f4b0da8b039c131&stat=instructions:u) (up to 4.3% on `full` builds of `wg-grammar-check`)
+- Seems to potentially be necessary, but difference from PR run suggests more
+  can possibly be done to avoid some of the losses noted on the final merge.
+
+Revert "Merge CrateDisambiguator into StableCrateId" [#85891](https://github.com/rust-lang/rust/issues/85891)
+- Moderate regression in [instruction counts](https://perf.rust-lang.org/compare.html?start=022720bfccd46400e69def42f4647fe4059ad951&end=2312ff1a850db449b79fd3c4b215395cd2598c25&stat=instructions:u) (up to 4.9% on `full` builds of `html5ever-opt`)
+- Reverted due to performance concerns on the original PR ([#85804]), but does
+  not seem to have recovered performance. Suggested path is to re-land but with
+  measurements the original PR; potentially there are some performance
+  improvements that can be done there as well.
+
+[#85804]: https://github.com/rust-lang/rust/pull/85804
+
+#### Improvements
+
+Remove CrateNum::ReservedForIncrCompCache [#85829](https://github.com/rust-lang/rust/issues/85829)
+- Very large improvement in [instruction counts](https://perf.rust-lang.org/compare.html?start=7f9ab0300cd66f6f616e03ea90b2d71af474bf28&end=625d5a693e4697bcafdd34fd1a38c281acabb8e9&stat=instructions:u) (up to -11.2% on `full` builds of `deeply-nested-async-debug`)
+- Unclear what the exact cause of the large improvement is. It may be worth
+  investigating, as at first glance the change does not seem like it should have
+  such strong effects.
+
+Only compute the trait map once [#85905](https://github.com/rust-lang/rust/issues/85905)
+- Moderate improvement in [instruction counts](https://perf.rust-lang.org/compare.html?start=c4f186f0ea443db4aacdd90a2515632c20ccd3fe&end=d20b9add05d32761abad651f568f1b1831cb8cf6&stat=instructions:u) (up to -1.6% on `incr-unchanged` builds of `cranelift-codegen-check`)
+
+Miscellaneous inlining improvements [#85892](https://github.com/rust-lang/rust/issues/85892)
+- Moderate improvement in [instruction counts](https://perf.rust-lang.org/compare.html?start=7350f655ef7e1b00f287eca6f8c0016a8985900c&end=1e13a9bb33debb931d603278b7f1a706b0d11660&stat=instructions:u) (up to -2.2% on `full` builds of `ctfe-stress-4-check`)
+
+#### Mixed
+
+Rollup of 13 pull requests [#85952](https://github.com/rust-lang/rust/issues/85952)
+- Moderate improvement in [instruction counts](https://perf.rust-lang.org/compare.html?start=016e9b5e33ef1407bffb575ec63d24241912556d&end=a93699f20a433797a4b84787b9652300dd7b2ad2&stat=instructions:u) (up to -4.8% on `full` builds of `html5ever-opt`)
+- Moderate regression in [instruction counts](https://perf.rust-lang.org/compare.html?start=016e9b5e33ef1407bffb575ec63d24241912556d&end=a93699f20a433797a4b84787b9652300dd7b2ad2&stat=instructions:u) (up to 2.9% on `incr-patched: println` builds of `cargo-opt`)
+- Predominantly an improvement, some incremental regressions; does not appear
+  worthwhile to investigate in depth the exact cause.
+
+#### Nags requiring follow up
+
+* Follow up on regression in [#85343](https://github.com/rust-lang/rust/pull/85343#issuecomment-856819536)