[Perf] Linux/arm64: 1 Regression on 8/14/2026 7:15:06 PM +00:00

### Run Information

Name | Value
-- | --
Architecture | arm64
OS | azurelinux 3.0
Queue | CobaltAzureLinux
Baseline | [afb1dc1f8fbffeb5afda4ec624695ae8ddd2960d](https://github.com/dotnet/runtime/commit/afb1dc1f8fbffeb5afda4ec624695ae8ddd2960d)
Compare | [c99188c2f97b94c8b086cc9b87516b6d710ec4ff](https://github.com/dotnet/runtime/commit/c99188c2f97b94c8b086cc9b87516b6d710ec4ff)
Diff | [Diff](https://github.com/dotnet/runtime/compare/afb1dc1f8fbffeb5afda4ec624695ae8ddd2960d...c99188c2f97b94c8b086cc9b87516b6d710ec4ff)
Configs | CompilationMode:tiered, R2RType:r2r_interpreter, RunKind:micro

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

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]()

![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>.LastIndexOfAnyValues(Size: 512)

#### 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 106-107 and compare the baseline and test commits listed in the issue. Run the provided benchmarks_ci.py command with the System.Memory.Span filter, then investigate the LastIndexOfAnyValues regression on Linux/arm64. Done means the regression is explained and the benchmark no longer shows the reported slowdown.

Written by the indexing model from the issue text.