[Perf] Linux/x64: 2 Regressions on 7/19/2026 5:54:44 PM +00:00

### Run Information

Name | Value
-- | --
Architecture | x64
OS | ubuntu 22.04
Queue | ViperUbuntu
Baseline | [b78a8f8b1d15898ba39eb4fd63e2578edcf16c37](https://github.com/dotnet/runtime/commit/b78a8f8b1d15898ba39eb4fd63e2578edcf16c37)
Compare | [f43516f45fff5920eabd11753bd5f1803cfacd0c](https://github.com/dotnet/runtime/commit/f43516f45fff5920eabd11753bd5f1803cfacd0c)
Diff | [Diff](https://github.com/dotnet/runtime/compare/b78a8f8b1d15898ba39eb4fd63e2578edcf16c37...f43516f45fff5920eabd11753bd5f1803cfacd0c)
Configs | AOT:true, CompilationMode:wasm, RunKind:micro

### Regressions in System.Globalization.Tests.Perf_NumberCultureInfo

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

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

| 189.12 ns | 211.56 ns | 1.12 | 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.Globalization.Tests.Perf_NumberCultureInfo*'
```

### System.Globalization.Tests.Perf_NumberCultureInfo.ToString(culturestring: fr)

#### 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 | [b78a8f8b1d15898ba39eb4fd63e2578edcf16c37](https://github.com/dotnet/runtime/commit/b78a8f8b1d15898ba39eb4fd63e2578edcf16c37)
Compare | [f43516f45fff5920eabd11753bd5f1803cfacd0c](https://github.com/dotnet/runtime/commit/f43516f45fff5920eabd11753bd5f1803cfacd0c)
Diff | [Diff](https://github.com/dotnet/runtime/compare/b78a8f8b1d15898ba39eb4fd63e2578edcf16c37...f43516f45fff5920eabd11753bd5f1803cfacd0c)
Configs | AOT:true, CompilationMode:wasm, RunKind:micro

### Regressions in Microsoft.Extensions.Primitives.StringSegmentBenchmark

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

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

| 38.23 ns | 40.63 ns | 1.06 | 0.13 | 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 'Microsoft.Extensions.Primitives.StringSegmentBenchmark*'
```

### Microsoft.Extensions.Primitives.StringSegmentBenchmark.Indexer

#### 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/libraries/System.Globalization/Perf.NumberCultureInfo.cs and src/benchmarks/micro/libraries/Microsoft.Extensions.Primitives/StringSegmentBenchmark.cs, then run the two benchmark commands in the Repro sections. Compare results with the listed baseline and compare commits and inspect the linked reports. Done means the regressions are explained and the affected benchmarks no longer show the reported slowdown.

Written by the indexing model from the issue text.