[Perf] Linux/arm64: 2 Regressions on 4/28/2026 1:30:15 PM +00:00

### Run Information

Name | Value
-- | --
Architecture | arm64
OS | azurelinux 3.0
Queue | CobaltAzureLinux
Baseline | [a9bbe530c25e60e1da9cf29f3646062498d69b28](https://github.com/dotnet/runtime/commit/a9bbe530c25e60e1da9cf29f3646062498d69b28)
Compare | [5391e9ec4fb4ab1bcebe4dbfc33bf4b8fdf01981](https://github.com/dotnet/runtime/commit/5391e9ec4fb4ab1bcebe4dbfc33bf4b8fdf01981)
Diff | [Diff](https://github.com/dotnet/runtime/compare/a9bbe530c25e60e1da9cf29f3646062498d69b28...5391e9ec4fb4ab1bcebe4dbfc33bf4b8fdf01981)
Configs | CompilationMode:tiered, RunKind:micro

### Regressions in Span.IndexerBench

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

• [KnownSizeCtor2 - Duration of single invocation]()
• 📝 - [Benchmark Source]()
• [ADX - Test Multi Config Graph]()

| 763.09 ns | 975.92 ns | 1.28 | 0.16 | 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
py .\performance\scripts\benchmarks_ci.py -f net8.0 --filter 'Span.IndexerBench*'
```

### Span.IndexerBench.KnownSizeCtor2(length: 1024)

#### 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 | azurelinux 3.0
Queue | CobaltAzureLinux
Baseline | [a9bbe530c25e60e1da9cf29f3646062498d69b28](https://github.com/dotnet/runtime/commit/a9bbe530c25e60e1da9cf29f3646062498d69b28)
Compare | [5391e9ec4fb4ab1bcebe4dbfc33bf4b8fdf01981](https://github.com/dotnet/runtime/commit/5391e9ec4fb4ab1bcebe4dbfc33bf4b8fdf01981)
Diff | [Diff](https://github.com/dotnet/runtime/compare/a9bbe530c25e60e1da9cf29f3646062498d69b28...5391e9ec4fb4ab1bcebe4dbfc33bf4b8fdf01981)
Configs | CompilationMode:tiered, RunKind:micro

### Regressions in System.Numerics.Tests.Perf_BitOperations

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

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

| 1.26 μs | 1.45 μs | 1.15 | 0.15 | 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
py .\performance\scripts\benchmarks_ci.py -f net8.0 --filter 'System.Numerics.Tests.Perf_BitOperations*'
```

### System.Numerics.Tests.Perf_BitOperations.PopCount_uint

#### 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)