[Perf] Linux/x64: 2 Regressions on 8/21/2026 7:05:07 PM +00:00

### Run Information

Name | Value
-- | --
Architecture | x64
OS | ubuntu 22.04
Queue | ViperUbuntu
Baseline | [76c60b960a2daa412c44a5061abf66f3286f6a92](https://github.com/dotnet/runtime/commit/76c60b960a2daa412c44a5061abf66f3286f6a92)
Compare | [58a829968e8d2624cbcb4e2ce7f1bb01cb9f652b](https://github.com/dotnet/runtime/commit/58a829968e8d2624cbcb4e2ce7f1bb01cb9f652b)
Diff | [Diff](https://github.com/dotnet/runtime/compare/76c60b960a2daa412c44a5061abf66f3286f6a92...58a829968e8d2624cbcb4e2ce7f1bb01cb9f652b)
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
-- | -- | -- | -- | -- | -- | -- | -- | --
|

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

| 550.34 ns | 693.45 ns | 1.26 | 0.24 | 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
python3 .\performance\scripts\benchmarks_ci.py -f net8.0 --filter 'PerfLabTests.CastingPerf*'
```

### PerfLabTests.CastingPerf.CheckArrayIsVariantGenericInterfaceNo

#### 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 | x64
OS | ubuntu 22.04
Queue | ViperUbuntu
Baseline | [76c60b960a2daa412c44a5061abf66f3286f6a92](https://github.com/dotnet/runtime/commit/76c60b960a2daa412c44a5061abf66f3286f6a92)
Compare | [58a829968e8d2624cbcb4e2ce7f1bb01cb9f652b](https://github.com/dotnet/runtime/commit/58a829968e8d2624cbcb4e2ce7f1bb01cb9f652b)
Diff | [Diff](https://github.com/dotnet/runtime/compare/76c60b960a2daa412c44a5061abf66f3286f6a92...58a829968e8d2624cbcb4e2ce7f1bb01cb9f652b)
Configs | CompilationMode:wasm, RunKind:micro, RuntimeType:coreclr

### Regressions in System.Collections.CtorFromCollection<String>

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

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

| 3.69 μs | 4.03 μs | 1.09 | 0.28 | 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
python3 .\performance\scripts\benchmarks_ci.py -f net8.0 --filter 'System.Collections.CtorFromCollection*'
```

### System.Collections.CtorFromCollection<String>.ImmutableArray(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 linked benchmark sources, src/benchmarks/micro/runtime/perflab/CastingPerf.cs and src/benchmarks/micro/libraries/System.Collections/Create/CtorFromCollection.cs, then run the provided benchmarks_ci.py filters. Compare the reported results with the baseline and comparison commits. Done means the two performance regressions are explained and addressed or triaged with supporting benchmark results.

Written by the indexing model from the issue text.