[Perf] Linux/x64: 2 Regressions on 8/14/2026 10:22:33 AM +00:00

### Run Information

Name | Value
-- | --
Architecture | x64
OS | ubuntu 22.04
Queue | ViperUbuntu
Baseline | [d00a0a24912957046ed2443adc0af7bbfb4c43bc](https://github.com/dotnet/runtime/commit/d00a0a24912957046ed2443adc0af7bbfb4c43bc)
Compare | [420dfbb4f584c1b0ddebec9615d1a673437050f6](https://github.com/dotnet/runtime/commit/420dfbb4f584c1b0ddebec9615d1a673437050f6)
Diff | [Diff](https://github.com/dotnet/runtime/compare/d00a0a24912957046ed2443adc0af7bbfb4c43bc...420dfbb4f584c1b0ddebec9615d1a673437050f6)
Configs | AOT:true, CompilationMode:wasm, RunKind:micro

### Regressions in Span.IndexerBench

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

• [Indexer4 - Duration of single invocation]()
• 📝 - [Benchmark Source]()
• [ADX - Test Multi Config Graph]()

| 3.06 μs | 4.00 μs | 1.30 | 0.00 | False | | |
|

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

| 356.30 ns | 380.95 ns | 1.07 | 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 'Span.IndexerBench*'
```

### Span.IndexerBench.Indexer4(length: 1024)

#### ETL Files

#### Histogram

#### JIT Disasms

### 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)

Start with src/benchmarks/micro/runtime/Span/Indexer.cs, especially the Indexer4 and KnownSizeCtor2 benchmarks, and run the provided benchmarks_ci.py command. Compare the baseline and compare commits and use the linked test reports to investigate both regressions. Done means the cause is identified and the reported benchmark regressions are resolved.

Written by the indexing model from the issue text.