Add triage report for this week

Author: Mark-Simulacrum

triage/2021-08-03.md

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+# 2021-08-03 Triage Log
+
+Quiet week for performance, with no large changes. Regressions are limited to
+just a few benchmarks.
+
+Triage done by **@simulacrum**.
+Revision range: [998cfe5aad7c21eb19a4bca50f05a13354706970..3354a44d2fa8d5ba6b8d6b40d2596de2c8292ec1](https://perf.rust-lang.org/?start=998cfe5aad7c21eb19a4bca50f05a13354706970&end=3354a44d2fa8d5ba6b8d6b40d2596de2c8292ec1&absolute=false&stat=instructions%3Au)
+
+2 Regressions, 0 Improvements, 0 Mixed; 1 of them in rollups
+
+#### Regressions
+
+Rollup of 9 pull requests [#87640](https://github.com/rust-lang/rust/issues/87640)
+- Moderate regression in [instruction counts](https://perf.rust-lang.org/compare.html?start=ef9549b6c0efb7525c9b012148689c8d070f9bc0&end=1f0a591b3a5963a0ab11a35dc525ad9d46f612e4&stat=instructions:u) (up to 1.4% on `incr-unchanged` builds of `html5ever-check`)
+- Regressions across a few benchmarks, without an obvious cause. May be due to
+  [#87385](https://github.com/rust-lang/rust/pull/87385), but logs don't appear
+  to show the warning in those crates at a cursory check. Tagged with
+  perf-regression for further investigation.
+
+Implement advance_by, advance_back_by for slice::{Iter, IterMut} [#87387](https://github.com/rust-lang/rust/issues/87387)
+- Moderate regression in [instruction counts](https://perf.rust-lang.org/compare.html?start=b289bb7fdfcb6f54d825927ab9b5722cabc2a140&end=6b0b07d41f07e1ba5808693d900903499ccf7a32&stat=instructions:u) (up to 1.6% on `full` builds of `regex-opt`)
+- Unclear cause, likely LLVM-related.
+
+#### Improvements
+
+- None this week.
+
+#### Mixed
+
+- None this week.
+
+#### Untriaged Pull Requests
+
+- [#87244 Better diagnostics with mismatched types due to implicit static lifetime](https://github.com/rust-lang/rust/pull/87244)
+- [#86777 Include terminators in instance size estimate](https://github.com/rust-lang/rust/pull/86777)
+- [#86698 Move OnDiskCache to rustc_query_impl.](https://github.com/rust-lang/rust/pull/86698)
+- [#86588 Rollup of 8 pull requests](https://github.com/rust-lang/rust/pull/86588)
+- [#86034 Change entry point to 🛡️ against 💥 💥-payloads](https://github.com/rust-lang/rust/pull/86034)
+- [#84560 Inline Iterator as IntoIterator.](https://github.com/rust-lang/rust/pull/84560)