[Perf] Windows/x86: 1 Regression on 7/17/2026 3:20:10 PM +00:00

### Run Information

Name | Value
-- | --
Architecture | x86
OS | Windows 10.0.22631
Queue | ViperWindows
Baseline | [509acfd47f3cbbaeddb6a49edadaedb8fdfdf9ad](https://github.com/dotnet/runtime/commit/509acfd47f3cbbaeddb6a49edadaedb8fdfdf9ad)
Compare | [1c124aa4de6f37b96572de3d429a611260a29a23](https://github.com/dotnet/runtime/commit/1c124aa4de6f37b96572de3d429a611260a29a23)
Diff | [Diff](https://github.com/dotnet/runtime/compare/509acfd47f3cbbaeddb6a49edadaedb8fdfdf9ad...1c124aa4de6f37b96572de3d429a611260a29a23)
Configs | CompilationMode:tiered, RunKind:micro

### Regressions in Microsoft.Extensions.Primitives.StringSegmentBenchmark

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

• [Indexer - Duration of single invocation]()
• 📝 - [Benchmark Source]()
• [ADX - Test Multi Config 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 'Microsoft.Extensions.Primitives.StringSegmentBenchmark*'
```

### Microsoft.Extensions.Primitives.StringSegmentBenchmark.Indexer

#### 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 the Microsoft.Extensions.Primitives.StringSegmentBenchmark source at src/benchmarks/micro/libraries/Microsoft.Extensions.Primitives/StringSegmentBenchmark.cs and reproduce the Indexer benchmark using the provided benchmarks_ci.py command. Compare the listed baseline and test commits and use the linked report and history graph to investigate the 24% regression; done means the regression is explained and the benchmark returns toward its baseline.

Written by the indexing model from the issue text.