[Perf] Windows/x86: 2 Regressions on 8/27/2026 8:39:22 PM +00:00

### Run Information

Name | Value
-- | --
Architecture | x86
OS | Windows 10.0.22631
Queue | ViperWindows
Baseline | [9632f7fec2888b1dd86ac3271ca7516fc680c81d](https://github.com/dotnet/runtime/commit/9632f7fec2888b1dd86ac3271ca7516fc680c81d)
Compare | [3174387aedaebdb35da41426e61ecc1b8d60bc47](https://github.com/dotnet/runtime/commit/3174387aedaebdb35da41426e61ecc1b8d60bc47)
Diff | [Diff](https://github.com/dotnet/runtime/compare/9632f7fec2888b1dd86ac3271ca7516fc680c81d...3174387aedaebdb35da41426e61ecc1b8d60bc47)
Configs | CompilationMode:tiered, RunKind:micro

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

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

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

| 214.67 μs | 252.41 μs | 1.18 | 0.37 | 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
py .\performance\scripts\benchmarks_ci.py -f net8.0 --filter 'System.Collections.ContainsFalse*'
```

### System.Collections.ContainsFalse<String>.Stack(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)

---

### Run Information

Name | Value
-- | --
Architecture | x86
OS | Windows 10.0.22631
Queue | ViperWindows
Baseline | [9632f7fec2888b1dd86ac3271ca7516fc680c81d](https://github.com/dotnet/runtime/commit/9632f7fec2888b1dd86ac3271ca7516fc680c81d)
Compare | [3174387aedaebdb35da41426e61ecc1b8d60bc47](https://github.com/dotnet/runtime/commit/3174387aedaebdb35da41426e61ecc1b8d60bc47)
Diff | [Diff](https://github.com/dotnet/runtime/compare/9632f7fec2888b1dd86ac3271ca7516fc680c81d...3174387aedaebdb35da41426e61ecc1b8d60bc47)
Configs | CompilationMode:tiered, RunKind:micro

### Regressions in System.Text.RegularExpressions.Tests.Perf_Regex_Industry_Rebar_Russian

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

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

| 310.96 μs | 398.84 μs | 1.28 | 0.36 | 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
py .\performance\scripts\benchmarks_ci.py -f net8.0 --filter 'System.Text.RegularExpressions.Tests.Perf_Regex_Industry_Rebar_Russian*'
```

### System.Text.RegularExpressions.Tests.Perf_Regex_Industry_Rebar_Russian.Count(Pattern: "(?i)Шерлок Холмс", Options: None)

#### 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 benchmark sources src/benchmarks/micro/libraries/System.Collections/Contains/ContainsFalse.cs and src/benchmarks/micro/libraries/System.Text.RegularExpressions/Perf.Regex.Industry.cs, then run the provided benchmarks_ci.py commands on Windows x86. Compare the baseline and compare commits and their performance reports to identify the regression cause; done means the cause is understood and a validated corrective change or triage result is recorded.

Written by the indexing model from the issue text.