Merge pull request #1088 from pnkfelix/triage-2021-11-02

perf triage for this week.

Author: Mark-Simulacrum

triage/2021-11-02.md

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+# 2021-11-02 Triage Log
+
+Summary: The only significant regressions were 1. two PRs that slowed down doc
+generation, and 2. some slowdown from the new lints to flag occurrences of
+Unicode bidirectional control characters. The doc generation regression is being
+investigated.
+
+Triage done by **@pnkfelix**.
+Revision range: [3c8f001d454b1b495f7472d8430ef8fdf10aac11..6384dca100f3cedfa031a9204586f94f8612eae5](https://perf.rust-lang.org/?start=3c8f001d454b1b495f7472d8430ef8fdf10aac11&end=6384dca100f3cedfa031a9204586f94f8612eae5&absolute=false&stat=instructions%3Au)
+
+6 Regressions, 3 Improvements, 1 Mixed; 4 of them in rollups
+39 comparisons made in total
+
+#### Regressions
+
+Fixes incorrect handling of ADT's drop requirements [#90218](https://github.com/rust-lang/rust/issues/90218)
+- Very large regression in [instruction counts](https://perf.rust-lang.org/compare.html?start=c4ff03f689c03d73d3a8af49611b1f2b54d6a300&end=85c0558d032e204f4f4ed6137f3119cb92dbc684&stat=instructions:u) (up to 5.3% on `full` builds of `regression-31157`)
+- regression-31157 check regressed by 4.7% on incr and 5.3 on full.
+- issue-46449 check regressed by 1.89% on incr-full.
+- wg-grammar regressed by 1.3-1.4% in a bunch of scenarios.
+- but otherwise, this does not seem too bad. I think we should keep this PR approved for backport, while also look into fixing the regression on nightly.
+- filed [#90504](https://github.com/rust-lang/rust/issues/90504) as followup investigation issue.
+
+Rollup of 3 pull requests [#90387](https://github.com/rust-lang/rust/issues/90387)
+- Large regression in [instruction counts](https://perf.rust-lang.org/compare.html?start=c390d69a615f095208ac94841f3310268521b2ee&end=df76418f1ee1a1973e862828ae8520abb6c3794a&stat=instructions:u) (up to 2.4% on `full` builds of `inflate`)
+- 2 of the 3 pull requests appear trivial (fixing typos and removing extra lines in documentation), which leaves [PR #90376](https://github.com/rust-lang/rust/pull/90376) as the main suspect.
+- Meanwhile, all [PR #90376](https://github.com/rust-lang/rust/pull/90376) does, according to its description, is move code around, remove dead code, and inline a singly called function.
+- treating as alignment artifacts from code rearrangement. We tend not to micro-optimize that in the compiler.
+
+Rollup of 8 pull requests [#90416](https://github.com/rust-lang/rust/issues/90416)
+- Large regression in [instruction counts](https://perf.rust-lang.org/compare.html?start=2b643e987173b36cb0279a018579372e31a35776&end=9f13083542cb2b9fce83ed8a50238e4a6386820f&stat=instructions:u) (up to 2.7% on `full` builds of `helloworld`)
+- All the significant perf regressions are due to doc generation (many regressed by 1.0-2.7%).
+- filed [#90512](https://github.com/rust-lang/rust/issues/90512) as followup investigation issue.
+
+Rollup of 5 pull requests [#90422](https://github.com/rust-lang/rust/issues/90422)
+- Very large regression in [instruction counts](https://perf.rust-lang.org/compare.html?start=2609fab8e46414333aa68412134df65c7fcd1a77&end=e249ce6b2345587d6e11052779c86adbad626dff&stat=instructions:u) (up to 5.8% on `full` builds of `tokio-webpush-simple`)
+- All the significant perf regressions are due to doc generation (many regressed by 1.0-5.8%).
+- discussion is ongoing in [PR 90183](https://github.com/rust-lang/rust/pull/90183)
+
+impl Pattern for char array [#86336](https://github.com/rust-lang/rust/issues/86336)
+- Small regression in [instruction counts](https://perf.rust-lang.org/compare.html?start=68b554e6af18726fe6fa8de2134c59c441e0b019&end=c7e4740ec18996e082fe6e29ebf7efdc7dda418f&stat=instructions:u) (up to 0.6% on `full` builds of `deeply-nested-async`)
+- The only benchmarks that regressed did so by a small amount, percentage wise 0.2-0.6%; the benchmarks that did regress in that fashion are: `deeply-nested-async`, `helloworld`, `unify-linearly`.
+- I don't think its worth investing effort trying to figure out the root cause of this minor regression, unless someone wants to take it on as a self-educating exercise.
+
+Update cargo [#90490](https://github.com/rust-lang/rust/issues/90490)
+- Moderate regression in [instruction counts](https://perf.rust-lang.org/compare.html?start=6225262562f06d8a52624e7898098b58789a6ae5&end=dca3f1b786efd27be3b325ed1e01e247aa589c3b&stat=instructions:u) (up to 2.0% on `incr-patched: println` builds of `regression-31157`)
+- Only regression-31157 opt regressed, by 1.6-2.0%.
+- It is not worth investing effort trying to figure out the root cause of this limited regression.
+- (Note: regression [#31157](https://github.com/rust-lang/rust/issues/31157) was itself put in to catch a performance regression with respect to time and RAM, but that regression was more like 1,882% in time and 10x in space.)
+
+#### Improvements
+
+Rollup of 4 pull requests [#90314](https://github.com/rust-lang/rust/issues/90314)
+- Large improvement in [instruction counts](https://perf.rust-lang.org/compare.html?start=612356aa9a0193cb5aee2b668b3893ddf67da2b5&end=e269e6bf47f40c9046cd44ab787881d700099252&stat=instructions:u) (up to -2.1% on `incr-unchanged` builds of `helloworld`)
+
+Use SortedMap in HIR. [#90145](https://github.com/rust-lang/rust/issues/90145)
+- Moderate improvement in [instruction counts](https://perf.rust-lang.org/compare.html?start=f2707fec04f655cdf18388618881748ebbd683e9&end=c4ff03f689c03d73d3a8af49611b1f2b54d6a300&stat=instructions:u) (up to -0.8% on `incr-unchanged` builds of `unicode_normalization`)
+
+Revert "Add rustc lint, warning when iterating over hashmaps" [#90380](https://github.com/rust-lang/rust/issues/90380)
+- Very large improvement in [instruction counts](https://perf.rust-lang.org/compare.html?start=a9f664f37d62fd255827a416482186308b8e8f7d&end=88a5a984fe95e0411dce4e8364f9630cadd3782c&stat=instructions:u) (up to -8.9% on `incr-full` builds of `deeply-nested-async`)
+
+
+#### Mixed
+
+[master] Fix CVE-2021-42574 [#90462](https://github.com/rust-lang/rust/issues/90462)
+- Small improvement in [instruction counts](https://perf.rust-lang.org/compare.html?start=ff0e14829e1806ca0d4226595f7fdf3e8658758f&end=db14a17e69af2a2e241ce149a501a5281811fe06&stat=instructions:u) (up to -0.5% on `full` builds of `deeply-nested-async`)
+- Very large regression in [instruction counts](https://perf.rust-lang.org/compare.html?start=ff0e14829e1806ca0d4226595f7fdf3e8658758f&end=db14a17e69af2a2e241ce149a501a5281811fe06&stat=instructions:u) (up to 14.2% on `incr-unchanged` builds of `coercions`)
+- Filed [issue #90514](https://github.com/rust-lang/rust/issues/90514) for follow up investigation of coercions regression.
+
+#### Untriaged Pull Requests
+
+- [#90490 Update cargo](https://github.com/rust-lang/rust/pull/90490)
+- [#90462 [master] Fix CVE-2021-42574](https://github.com/rust-lang/rust/pull/90462)
+- [#90422 Rollup of 5 pull requests](https://github.com/rust-lang/rust/pull/90422)
+- [#90416 Rollup of 8 pull requests](https://github.com/rust-lang/rust/pull/90416)
+- [#90387 Rollup of 3 pull requests](https://github.com/rust-lang/rust/pull/90387)
+- [#90235 Rollup of 6 pull requests](https://github.com/rust-lang/rust/pull/90235)
+- [#90218 Fixes incorrect handling of ADT's drop requirements](https://github.com/rust-lang/rust/pull/90218)
+- [#90183 Show all Deref implementations recursively](https://github.com/rust-lang/rust/pull/90183)
+- [#90067 Rollup of 10 pull requests](https://github.com/rust-lang/rust/pull/90067)
+- [#89939 Rollup of 10 pull requests](https://github.com/rust-lang/rust/pull/89939)
+- [#89858 Rollup of 6 pull requests](https://github.com/rust-lang/rust/pull/89858)
+- [#89695 Move top part of print_item to Tera templates](https://github.com/rust-lang/rust/pull/89695)
+- [#89608 Rollup of 12 pull requests](https://github.com/rust-lang/rust/pull/89608)
+- [#89534 Introduce `tcx.get_diagnostic_name`](https://github.com/rust-lang/rust/pull/89534)
+- [#89435 Rollup of 6 pull requests](https://github.com/rust-lang/rust/pull/89435)
+- [#89405 Fix clippy lints](https://github.com/rust-lang/rust/pull/89405)
+- [#89263 Suggest both of immutable and mutable trait implementations](https://github.com/rust-lang/rust/pull/89263)
+- [#89165 Fix read_to_end to not grow an exact size buffer](https://github.com/rust-lang/rust/pull/89165)
+- [#89125 Don't use projection cache or candidate cache in intercrate mode](https://github.com/rust-lang/rust/pull/89125)
+- [#89124 Index and hash HIR as part of lowering](https://github.com/rust-lang/rust/pull/89124)
+- [#89103 Migrate in-tree crates to 2021](https://github.com/rust-lang/rust/pull/89103)
+- [#89100 resolve: Use `NameBinding` for local variables and generic parameters](https://github.com/rust-lang/rust/pull/89100)
+- [#89047 Rollup of 10 pull requests](https://github.com/rust-lang/rust/pull/89047)
+- [#89030 Introduce `Rvalue::ShallowInitBox`](https://github.com/rust-lang/rust/pull/89030)
+- [#88945 Remove concept of 'completion' from the projection cache](https://github.com/rust-lang/rust/pull/88945)
+- [#88880 Rework HIR API to make invocations of the hir_crate query harder.](https://github.com/rust-lang/rust/pull/88880)
+- [#88824 Rollup of 15 pull requests](https://github.com/rust-lang/rust/pull/88824)
+- [#88804 Revise never type fallback algorithm](https://github.com/rust-lang/rust/pull/88804)
+- [#88719 Point at argument instead of call for their obligations](https://github.com/rust-lang/rust/pull/88719)
+- [#88703 Gather module items after lowering.](https://github.com/rust-lang/rust/pull/88703)