[Perf] Linux/x64: 2 Regressions on 8/5/2026 6:23:30 AM +00:00

### Run Information

Name | Value
-- | --
Architecture | x64
OS | ubuntu 22.04
Queue | ViperUbuntu
Baseline | [f107b2325cccfd453f9bf46013159f4704ea56c2](https://github.com/dotnet/runtime/commit/f107b2325cccfd453f9bf46013159f4704ea56c2)
Compare | [b6caa7d9ec9b346b2b09a31ab3fccfe7d049b723](https://github.com/dotnet/runtime/commit/b6caa7d9ec9b346b2b09a31ab3fccfe7d049b723)
Diff | [Diff](https://github.com/dotnet/runtime/compare/f107b2325cccfd453f9bf46013159f4704ea56c2...b6caa7d9ec9b346b2b09a31ab3fccfe7d049b723)
Configs | CompilationMode:wasm, RunKind:micro, RuntimeType:coreclr

### Regressions in PerfLabTests.CastingPerf

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

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

| 560.48 ns | 795.23 ns | 1.42 | 0.26 | False | | |
|

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

| 569.82 ns | 770.47 ns | 1.35 | 0.25 | 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 'PerfLabTests.CastingPerf*'
```

### PerfLabTests.CastingPerf.CheckArrayIsArrayByVariance

#### ETL Files

#### Histogram

#### JIT Disasms

### PerfLabTests.CastingPerf.CheckListIsVariantGenericInterface

#### 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/perflab/CastingPerf.cs at lines 400-412 and reproduce the two reported benchmarks with the documented benchmarks_ci.py command. Compare the baseline and test commits and use the linked performance and profiling reports to investigate the regression. Done means identifying the cause and resolving or validating the reported slowdown.

Written by the indexing model from the issue text.