[Perf] Windows/x86: 2 Regressions on 9/2/2026 11:01:35 AM +00:00

### Run Information

Name | Value
-- | --
Architecture | x86
OS | Windows 10.0.22631
Queue | ViperWindows
Baseline | [600c5b67ae4680acf39f6e85529973930bda4168](https://github.com/dotnet/runtime/commit/600c5b67ae4680acf39f6e85529973930bda4168)
Compare | [399c3eb8ba823f00f9a250de4a3cdbdfb5d18f33](https://github.com/dotnet/runtime/commit/399c3eb8ba823f00f9a250de4a3cdbdfb5d18f33)
Diff | [Diff](https://github.com/dotnet/runtime/compare/600c5b67ae4680acf39f6e85529973930bda4168...399c3eb8ba823f00f9a250de4a3cdbdfb5d18f33)
Configs | CompilationMode:tiered, RunKind:micro

### Regressions in System.Text.RegularExpressions.Tests.Perf_Regex_Industry_Leipzig

Benchmark | Baseline | Test | Test/Base | Test Quality | Edge Detector | Baseline IR | Compare IR | IR Ratio
-- | -- | -- | -- | -- | -- | -- | -- | --
|

• [Count - Duration of single invocation]()
• 📝 - [Benchmark Source]()
• [ADX - Test Multi Config Graph]()

| 27.42 ms | 30.28 ms | 1.10 | 0.02 | False | | |
|

• [Count - Duration of single invocation]()
• 📝 - [Benchmark Source]()
• [ADX - Test Multi Config Graph]()

| 27.48 ms | 30.27 ms | 1.10 | 0.01 | False | | |

![graph]()
![graph]()
[Test Report]()

### Repro
General Docs link: https://github.com/dotnet/performance/blob/main/docs/benchmarking-workflow-dotnet-runtime.md

```cmd
git clone https://github.com/dotnet/performance.git
py .\performance\scripts\benchmarks_ci.py -f net8.0 --filter 'System.Text.RegularExpressions.Tests.Perf_Regex_Industry_Leipzig*'
```

### System.Text.RegularExpressions.Tests.Perf_Regex_Industry_Leipzig.Count(Pattern: "\\p{Sm}", Options: NonBacktracking)

#### ETL Files

#### Histogram

#### JIT Disasms

### System.Text.RegularExpressions.Tests.Perf_Regex_Industry_Leipzig.Count(Pattern: "\\p{Sm}", Options: None)

#### ETL Files

#### Histogram

#### JIT Disasms

### Docs

[Profiling workflow for dotnet/runtime repository](https://github.com/dotnet/performance/blob/master/docs/profiling-workflow-dotnet-runtime.md)
[Benchmarking workflow for dotnet/runtime repository](https://github.com/dotnet/performance/blob/master/docs/benchmarking-workflow-dotnet-runtime.md)

Start with src/benchmarks/micro/libraries/System.Text.RegularExpressions/Perf.Regex.Industry.cs at lines 242-244 and run the provided benchmarks_ci.py command for Perf_Regex_Industry_Leipzig. Compare the baseline and regression commits, then investigate the reported Windows/x86 slowdown. Done means the regression is explained and the benchmark no longer shows the reported performance loss.

Written by the indexing model from the issue text.