[Perf] Windows/x86: 9 Regressions on 7/13/2026 5:42:28 AM +00:00

### Run Information

Name | Value
-- | --
Architecture | x86
OS | Windows 10.0.22631
Queue | ViperWindows
Baseline | [8ba3455391cc51b9f639ba5baef5394b2d219050](https://github.com/dotnet/runtime/commit/8ba3455391cc51b9f639ba5baef5394b2d219050)
Compare | [a90733cc40d6c7037a37d9c2b5c2403b8cac490f](https://github.com/dotnet/runtime/commit/a90733cc40d6c7037a37d9c2b5c2403b8cac490f)
Diff | [Diff](https://github.com/dotnet/runtime/compare/8ba3455391cc51b9f639ba5baef5394b2d219050...a90733cc40d6c7037a37d9c2b5c2403b8cac490f)
Configs | CompilationMode:tiered, RunKind:micro

### Regressions in System.IO.Tests.StreamReaderReadToEndTests

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

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

| 152.96 ms | 175.16 ms | 1.15 | 0.14 | False | | |
|

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

| 152.11 ms | 169.58 ms | 1.11 | 0.13 | False | | |
|

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

| 152.85 ms | 170.15 ms | 1.11 | 0.11 | False | | |
|

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

| 154.59 ms | 171.27 ms | 1.11 | 0.14 | False | | |
|

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

| 153.57 ms | 169.42 ms | 1.10 | 0.13 | False | | |
|

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

| 154.15 ms | 170.03 ms | 1.10 | 0.13 | False | | |
|

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

| 150.84 ms | 165.27 ms | 1.10 | 0.14 | False | | |
|

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

| 155.75 ms | 165.22 ms | 1.06 | 0.13 | False | | |
|

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

| 156.20 ms | 164.20 ms | 1.05 | 0.11 | False | | |

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[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.IO.Tests.StreamReaderReadToEndTests*'
```

### System.IO.Tests.StreamReaderReadToEndTests.ReadToEnd(LineLengthRange: [ 1, 1])

#### ETL Files

#### Histogram

#### JIT Disasms

### System.IO.Tests.StreamReaderReadToEndTests.ReadToEndAsync(LineLengthRange: [ 1, 1])

#### ETL Files

#### Histogram

#### JIT Disasms

### System.IO.Tests.StreamReaderReadToEndTests.ReadToEndAsync(LineLengthRange: [ 33, 128])

#### ETL Files

#### Histogram

#### JIT Disasms

### System.IO.Tests.StreamReaderReadToEndTests.ReadToEndAsync(LineLengthRange: [ 1, 8])

#### ETL Files

#### Histogram

#### JIT Disasms

### System.IO.Tests.StreamReaderReadToEndTests.ReadToEndAsync(LineLengthRange: [ 129, 1024])

#### ETL Files

#### Histogram

#### JIT Disasms

### System.IO.Tests.StreamReaderReadToEndTests.ReadToEnd(LineLengthRange: [ 33, 128])

#### ETL Files

#### Histogram

#### JIT Disasms

### System.IO.Tests.StreamReaderReadToEndTests.ReadToEnd(LineLengthRange: [ 1, 8])

#### ETL Files

#### Histogram

#### JIT Disasms

### System.IO.Tests.StreamReaderReadToEndTests.ReadToEnd(LineLengthRange: [ 129, 1024])

#### ETL Files

#### Histogram

#### JIT Disasms

### System.IO.Tests.StreamReaderReadToEndTests.ReadToEnd(LineLengthRange: [ 0, 0])

#### 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 source, dotnet/performance/src/benchmarks/micro/libraries/System.IO/StreamReaderReadToEndTests.cs, and review the baseline and compare commits in the Run Information. Reproduce the Windows x86 tiered microbenchmark and investigate the reported ReadToEnd and ReadToEndAsync regressions. Done means the cause is identified and the affected measurements no longer regress.

Written by the indexing model from the issue text.