Numerics.Vector.SinCos() bug

Start by running the supplied C# reproduction for Vector.SinCos with the lane-3 value changed between 0.0f and float.NaN. Trace the Vector.SinCos entry point and add a regression test covering the shown inputs; done means unaffected lanes produce identical sine and cosine results in both vectors.

Description

I am seeing Vector.SinCos() producing different results for identical inputs in a given lane when introducing a NaN in some other lane. Changing lane 3 from 0.0 to NaN causes Cos on lane 0 to change value.

Reproduction Steps

public void TestVectorSinCos()
{
    Vector<float> x = new Vector<float>([0.029831253f, 0.035057854f, 2.5535614f, 0.0f]);
    (var sinx, var cosx) = Vector.SinCos(x);

    Vector<float> y = new Vector<float>([0.029831253f, 0.035057854f, 2.5535614f, float.NaN]);
    (var siny, var cosy) = Vector.SinCos(y);

    for (int i = 0; i < 3; i++)
    {
        Assert.That(sinx[i], Is.EqualTo(siny[i]));
        Assert.That(cosx[i], Is.EqualTo(cosy[i]));
    }
}

Expected behavior

SIMD lanes should produce same the result for the same input.

Actual behavior

Cos on lane 0 changes from 0.9995551 to 0.99955505 when lane 3 changes from 0.0 to NaN. Each lane should operate independently.

Regression?

No response

Known Workarounds

Replace Vector sin and cos operations with scalar versions. But this has a negative performance impact.

Configuration

dotnet --info

.NET SDK:
 Version:           9.0.101
 Commit:            eedb237549
 Workload version:  9.0.100-manifests.4a280210
 MSBuild version:   17.12.12+1cce77968

Runtime Environment:
 OS Name:     Mac OS X
 OS Version:  15.3
 OS Platform: Darwin
 RID:         osx-arm64
 Base Path:   /usr/local/share/dotnet/sdk/9.0.101/

.NET workloads installed:
There are no installed workloads to display.
Configured to use loose manifests when installing new manifests.

Host:
  Version:      9.0.0
  Architecture: arm64
  Commit:       9d5a6a9aa4

.NET SDKs installed:
  6.0.301 [/usr/local/share/dotnet/sdk]
  8.0.203 [/usr/local/share/dotnet/sdk]
  9.0.101 [/usr/local/share/dotnet/sdk]

.NET runtimes installed:
  Microsoft.AspNetCore.App 6.0.6 [/usr/local/share/dotnet/shared/Microsoft.AspNetCore.App]
  Microsoft.AspNetCore.App 8.0.3 [/usr/local/share/dotnet/shared/Microsoft.AspNetCore.App]
  Microsoft.AspNetCore.App 9.0.0 [/usr/local/share/dotnet/shared/Microsoft.AspNetCore.App]
  Microsoft.NETCore.App 6.0.6 [/usr/local/share/dotnet/shared/Microsoft.NETCore.App]
  Microsoft.NETCore.App 8.0.3 [/usr/local/share/dotnet/shared/Microsoft.NETCore.App]
  Microsoft.NETCore.App 9.0.0 [/usr/local/share/dotnet/shared/Microsoft.NETCore.App]

Other architectures found:
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Environment variables:
  Not set

global.json file:
  Not found

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Other information

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