At some point recently, performance for BDN's compiled regex tests under the interpreter on wasm regressed by around 25-50x. See https://pvscmdupload.blob.core.windows.net/reports/allTestHistory/refs/heads/main_x64_ubuntu%2022.04_CompilationMode=wasm_RunKind=micro/System.Text.RegularExpressions.Tests.Perf_Regex_Common.MatchWord(Options%3a%20IgnoreCase%2c%20Compiled).html for one example.

I tested this in isolation and was able to reproduce bad performance, but I couldn't identify the cause, and the code involved is very complex so I couldn't make sense of what was going on. I didn't notice any misbehavior on the jiterpreter side of things for this scenario.

See dotnet/perf-autofiling-issues#29881 for diff range.