[Perf] Windows/x64: 2 Improvements on 7/20/2026 8:13:06 AM +00:00

### Run Information

Name | Value
-- | --
Architecture | x64
OS | Windows 10.0.22631
Queue | ViperWindows
Baseline | [c1b09d933f7d720f7ae50f80b4ec6980bb93d96f](https://github.com/dotnet/runtime/commit/c1b09d933f7d720f7ae50f80b4ec6980bb93d96f)
Compare | [dd5371130e5074f28aae46e00d54e24a220f743b](https://github.com/dotnet/runtime/commit/dd5371130e5074f28aae46e00d54e24a220f743b)
Diff | [Diff](https://github.com/dotnet/runtime/compare/c1b09d933f7d720f7ae50f80b4ec6980bb93d96f...dd5371130e5074f28aae46e00d54e24a220f743b)
Configs | CompilationMode:tiered, RunKind:micro

### Improvements in System.Memory.Span<Int32>

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

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

| 11.24 ns | 2.82 ns | 0.25 | 0.19 | False | | |
|

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

| 17.82 ns | 8.76 ns | 0.49 | 0.08 | 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.Memory.Span*'
```

### System.Memory.Span<Int32>.Fill(Size: 33)

#### ETL Files

#### Histogram

#### JIT Disasms

### System.Memory.Span<Int32>.Reverse(Size: 33)

#### 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 benchmark source at src/benchmarks/micro/libraries/System.Memory/Span.cs lines 53-57 and run the provided benchmarks_ci.py command with the System.Memory.Span filter. Compare the Fill and Reverse results with the linked reports; done means the reported performance behavior is understood and any justified optimization is validated by the benchmark.

Written by the indexing model from the issue text.