[Perf] Linux/x64: 3 Regressions on 7/31/2026 4:48:31 PM +00:00

### Run Information

Name | Value
-- | --
Architecture | x64
OS | ubuntu 22.04
Queue | ViperUbuntu
Baseline | [ba8afceee83540ed1d867987483f74d4ad2cfae9](https://github.com/dotnet/runtime/commit/ba8afceee83540ed1d867987483f74d4ad2cfae9)
Compare | [d5c739f99fa75a37ea863b06dd8d31a51965c8be](https://github.com/dotnet/runtime/commit/d5c739f99fa75a37ea863b06dd8d31a51965c8be)
Diff | [Diff](https://github.com/dotnet/runtime/compare/ba8afceee83540ed1d867987483f74d4ad2cfae9...d5c739f99fa75a37ea863b06dd8d31a51965c8be)
Configs | CompilationMode:wasm, RunKind:micro

### Regressions in System.Collections.Tests.Perf_BitArray

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

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

| 85.01 ns | 106.21 ns | 1.25 | 0.13 | False | | |
|

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

| 88.87 ns | 110.57 ns | 1.24 | 0.20 | False | | |
|

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

| 233.14 ns | 254.46 ns | 1.09 | 0.08 | False | | |

![graph]()
![graph]()
![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.Tests.Perf_BitArray*'
```

### System.Collections.Tests.Perf_BitArray.BitArrayIntArrayCtor(Size: 4)

#### ETL Files

#### Histogram

#### JIT Disasms

### System.Collections.Tests.Perf_BitArray.BitArrayBoolArrayCtor(Size: 4)

#### ETL Files

#### Histogram

#### JIT Disasms

### System.Collections.Tests.Perf_BitArray.BitArrayIntArrayCtor(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 src/benchmarks/micro/libraries/System.Collections/Perf.BitArray.cs at the linked benchmark definitions, then run scripts/benchmarks_ci.py with the provided filter. Compare the baseline and test commits and consult the profiling and benchmarking workflow docs. Done means reproducing the three regressions and documenting the responsible change or triage outcome.

Written by the indexing model from the issue text.