Latest manual perf run (.NET 6 vs .NET 7 preview 1) has discovered multiple regressions in System.Text.RegularExpressions. Since most of them were not reported previously, I am opening the issue, so the owners of System.Text.RegularExpressions can triage them accordingly.

I've uploaded a full report here. It's sorted desc from biggest regression to biggest improvement.

The @performanceautofiler has not reported these regressions as they were most likely introduced before the benchmarks were added in November 2021 (historical data)

Sample repro:

git clone https://github.com/dotnet/performance.git
py .\performance\scripts\benchmarks_ci.py -f net6.0 net7.0 --filter System.Text.RegularExpressions.Tests.Perf_Regex_Industry_RustLang_Sherlock.Count

Sample results:

System.Text.RegularExpressions.Tests.Perf_Regex_Industry_RustLang_Sherlock.Count(Pattern: "Sherlock|Holmes|Watson|Irene|Adler|John|Baker", Options: Compiled)

System.Text.RegularExpressions.Tests.Perf_Regex_Common.CtorInvoke(Options: Compiled)

(cc @stephentoub )