[Perf] Linux/arm64: 3 Improvements on 7/20/2026 4:17:25 AM +00:00

### Run Information

Name | Value
-- | --
Architecture | arm64
OS | ubuntu 22.04
Queue | AmpereUbuntu
Baseline | [cb301bc23e682da023cf3c51985d45fbb528e7c3](https://github.com/dotnet/runtime/commit/cb301bc23e682da023cf3c51985d45fbb528e7c3)
Compare | [d349aa7988e9adf0ee0f5f0473886c0582975955](https://github.com/dotnet/runtime/commit/d349aa7988e9adf0ee0f5f0473886c0582975955)
Diff | [Diff](https://github.com/dotnet/runtime/compare/cb301bc23e682da023cf3c51985d45fbb528e7c3...d349aa7988e9adf0ee0f5f0473886c0582975955)
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]()

| 34.44 μs | 32.18 μs | 0.93 | 0.00 | False | | |
|

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

| 34.40 μs | 32.18 μs | 0.94 | 0.00 | 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_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)

---

### Run Information

Name | Value
-- | --
Architecture | arm64
OS | ubuntu 22.04
Queue | AmpereUbuntu
Baseline | [cb301bc23e682da023cf3c51985d45fbb528e7c3](https://github.com/dotnet/runtime/commit/cb301bc23e682da023cf3c51985d45fbb528e7c3)
Compare | [d349aa7988e9adf0ee0f5f0473886c0582975955](https://github.com/dotnet/runtime/commit/d349aa7988e9adf0ee0f5f0473886c0582975955)
Diff | [Diff](https://github.com/dotnet/runtime/compare/cb301bc23e682da023cf3c51985d45fbb528e7c3...d349aa7988e9adf0ee0f5f0473886c0582975955)
Configs | CompilationMode:tiered, RunKind:micro

### Improvements in System.Memory.Span<Byte>

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

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

| 104.33 ns | 96.32 ns | 0.92 | 0.37 | False | | |

![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.Memory.Span*'
```

### System.Memory.Span<Byte>.LastIndexOfAnyValues(Size: 3000)

#### 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 linked benchmark sources in dotnet/performance, including src/benchmarks/micro/libraries/System.Runtime/Perf.Double.cs and System.Memory/Span.cs, then run scripts/benchmarks_ci.py with the filters shown. Compare the ARM64 Ubuntu results with the linked reports; the issue does not define a specific change or clear completion condition.

Written by the indexing model from the issue text.