[Perf] Linux/x64: 1 Regression on 8/8/2026 5:46:44 AM +00:00

### Run Information

Name | Value
-- | --
Architecture | x64
OS | ubuntu 22.04
Queue | ViperUbuntu
Baseline | [4c86c57ac3a6569063da4cb0a7245aadbc276f00](https://github.com/dotnet/runtime/commit/4c86c57ac3a6569063da4cb0a7245aadbc276f00)
Compare | [d9162a8b5629465d37d6881f377e5773c202d1f7](https://github.com/dotnet/runtime/commit/d9162a8b5629465d37d6881f377e5773c202d1f7)
Diff | [Diff](https://github.com/dotnet/runtime/compare/4c86c57ac3a6569063da4cb0a7245aadbc276f00...d9162a8b5629465d37d6881f377e5773c202d1f7)
Configs | AOT:true, CompilationMode:wasm, RunKind:micro

### Regressions in System.Linq.Tests.Perf_Enumerable

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

• [FirstWithPredicate_LastElementMatches - Duration of single invocation]()
• 📝 - [Benchmark Source]()
• [ADX - Test Multi Config 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.Linq.Tests.Perf_Enumerable*'
```

### System.Linq.Tests.Perf_Enumerable.FirstWithPredicate_LastElementMatches(input: List)

#### 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 System.Linq.Tests.Perf_Enumerable.FirstWithPredicate_LastElementMatches benchmark in performance/src/benchmarks/micro/libraries/System.Linq/Perf.Enumerable.cs and compare the baseline and test commits. Run the provided benchmarks_ci.py command, then use the linked report and profiling workflow to investigate the slowdown. Done means the regression is explained and addressed, with the benchmark no longer showing the unexplained increase.

Written by the indexing model from the issue text.