[Perf] Linux/x64: 2 Regressions on 8/19/2026 11:48:00 PM +00:00

### Run Information

Name | Value
-- | --
Architecture | x64
OS | ubuntu 22.04
Queue | ViperUbuntu
Baseline | [22645b47c400e6cc0aec97ddcb3f1998677b6d94](https://github.com/dotnet/runtime/commit/22645b47c400e6cc0aec97ddcb3f1998677b6d94)
Compare | [cb8ddc8cac0182e932903d921bd09300be7ae2a6](https://github.com/dotnet/runtime/commit/cb8ddc8cac0182e932903d921bd09300be7ae2a6)
Diff | [Diff](https://github.com/dotnet/runtime/compare/22645b47c400e6cc0aec97ddcb3f1998677b6d94...cb8ddc8cac0182e932903d921bd09300be7ae2a6)
Configs | CompilationMode:wasm, RunKind:micro, RuntimeType:coreclr

### Regressions in System.Tests.Perf_Single

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

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

| 31.22 μs | 42.01 μs | 1.35 | 0.17 | False | | |
|

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

| 41.64 μs | 53.09 μs | 1.28 | 0.20 | 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
python3 .\performance\scripts\benchmarks_ci.py -f net8.0 --filter 'System.Tests.Perf_Single*'
```

### System.Tests.Perf_Single.ToStringWithFormat(value: 12345, format: "G17")

#### ETL Files

#### Histogram

#### JIT Disasms

### System.Tests.Perf_Single.ToStringWithFormat(value: 12345, format: "F50")

#### 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.Runtime/Perf.Single.cs at lines 63-67 and compare the baseline and test commits linked in the report. Run the provided benchmarks_ci.py command for System.Tests.Perf_Single, then use the linked test reports and graphs to investigate both ToStringWithFormat regressions. Done means identifying the regression and documenting or resolving its cause.

Written by the indexing model from the issue text.