[Perf] Linux/x64: 2 Regressions on 9/7/2026 3:25:38 AM +00:00

### Run Information

Name | Value
-- | --
Architecture | x64
OS | ubuntu 22.04
Queue | ViperUbuntu
Baseline | [3b2b97b454ad0e3627f4fbc118f0284cb0ab07b5](https://github.com/dotnet/runtime/commit/3b2b97b454ad0e3627f4fbc118f0284cb0ab07b5)
Compare | [2120018b13c80b3bfff680dcfa93bc2e668664cc](https://github.com/dotnet/runtime/commit/2120018b13c80b3bfff680dcfa93bc2e668664cc)
Diff | [Diff](https://github.com/dotnet/runtime/compare/3b2b97b454ad0e3627f4fbc118f0284cb0ab07b5...2120018b13c80b3bfff680dcfa93bc2e668664cc)
Configs | CompilationMode:wasm, RunKind:micro

### Regressions in System.Runtime.Intrinsics.Tests.Perf_Vector128Of<Int32>

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

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

| 45.64 ns | 50.80 ns | 1.11 | 0.20 | 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.Runtime.Intrinsics.Tests.Perf_Vector128Of*'
```

### System.Runtime.Intrinsics.Tests.Perf_Vector128Of<Int32>.SquareRootBenchmark

#### 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 | [3b2b97b454ad0e3627f4fbc118f0284cb0ab07b5](https://github.com/dotnet/runtime/commit/3b2b97b454ad0e3627f4fbc118f0284cb0ab07b5)
Compare | [2120018b13c80b3bfff680dcfa93bc2e668664cc](https://github.com/dotnet/runtime/commit/2120018b13c80b3bfff680dcfa93bc2e668664cc)
Diff | [Diff](https://github.com/dotnet/runtime/compare/3b2b97b454ad0e3627f4fbc118f0284cb0ab07b5...2120018b13c80b3bfff680dcfa93bc2e668664cc)
Configs | CompilationMode:wasm, RunKind:micro

### Regressions in System.Memory.Slice<Byte>

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

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

| 41.16 ns | 43.66 ns | 1.06 | 0.08 | 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.Memory.Slice*'
```

### System.Memory.Slice<Byte>.ReadOnlyMemoryStartLengthSpan

#### 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 in performance/src/benchmarks/micro/libraries/System.Runtime.Intrinsics/Perf_Vector128OfT.cs and System.Memory/Slice.cs, then follow the benchmarking workflow documentation. Run benchmarks_ci.py with the two supplied filters and compare the baseline and regression commits; done means the regressions are explained and the relevant benchmark results are verified.

Written by the indexing model from the issue text.