[Perf] Linux/x64: 1 Regression on 9/1/2026 1:51:33 AM +00:00

### Run Information

Name | Value
-- | --
Architecture | x64
OS | ubuntu 22.04
Queue | ViperUbuntu
Baseline | [98a0a46bd543813f3e041c9e86650c2cdf20d7b6](https://github.com/dotnet/runtime/commit/98a0a46bd543813f3e041c9e86650c2cdf20d7b6)
Compare | [eaf33d448f75e519da20083ac9392098964d7c74](https://github.com/dotnet/runtime/commit/eaf33d448f75e519da20083ac9392098964d7c74)
Diff | [Diff](https://github.com/dotnet/runtime/compare/98a0a46bd543813f3e041c9e86650c2cdf20d7b6...eaf33d448f75e519da20083ac9392098964d7c74)
Configs | CompilationMode:wasm, RunKind:micro, RuntimeType:coreclr

### Regressions in System.Collections.ContainsKeyFalse<String, String>

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

• [ImmutableSortedDictionary - 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
python3 .\performance\scripts\benchmarks_ci.py -f net8.0 --filter 'System.Collections.ContainsKeyFalse*'
```

### System.Collections.ContainsKeyFalse<String, String>.ImmutableSortedDictionary(Size: 512)

#### 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.Collections/Contains/ContainsKeyFalse.cs at lines 127-136, then run the provided benchmarks_ci.py command and compare the listed baseline and test commits. Use the linked test report and profiling workflow documentation to identify the cause of the ImmutableSortedDictionary regression; done means the regression is explained and performance is restored or the result is triaged.

Written by the indexing model from the issue text.