[Perf] Linux/arm64: 2 Improvements on 7/20/2026 8:13:06 AM +00:00

### Run Information

Name | Value
-- | --
Architecture | arm64
OS | azurelinux 3.0
Queue | CobaltAzureLinux
Baseline | [f43516f45fff5920eabd11753bd5f1803cfacd0c](https://github.com/dotnet/runtime/commit/f43516f45fff5920eabd11753bd5f1803cfacd0c)
Compare | [dd5371130e5074f28aae46e00d54e24a220f743b](https://github.com/dotnet/runtime/commit/dd5371130e5074f28aae46e00d54e24a220f743b)
Diff | [Diff](https://github.com/dotnet/runtime/compare/f43516f45fff5920eabd11753bd5f1803cfacd0c...dd5371130e5074f28aae46e00d54e24a220f743b)
Configs | CompilationMode:tiered, RunKind:micro

### Improvements in System.Tests.Perf_Double

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]()

| 33.73 μs | 30.70 μs | 0.91 | 0.15 | False | | |
|

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

| 33.74 μs | 30.76 μs | 0.91 | 0.18 | 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.Tests.Perf_Double*'
```

### System.Tests.Perf_Double.ToStringWithFormat(value: 1.7976931348623157E+308, format: "F50")

#### ETL Files

#### Histogram

#### JIT Disasms

### System.Tests.Perf_Double.ToStringWithFormat(value: -1.7976931348623157E+308, 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.Double.cs lines 65-69 and the linked benchmark report, then run the provided benchmarks_ci.py command for System.Tests.Perf_Double. Done means reproducing and explaining the reported arm64 improvement, with any required follow-up grounded in the benchmark results.

Written by the indexing model from the issue text.