[tvOS][arm64] Vector128Tests.Vector128NIntSumTest/Vector128NUIntSumTest failed on the rolling build

[MaximLipnin]

<test name="System.Runtime.Intrinsics.Tests.Vectors.Vector128Tests.Vector128NIntSumTest" type="System.Runtime.Intrinsics.Tests.Vectors.Vector128Tests" method="Vector128NIntSumTest" time="0.0060218" result="Fail">
    <failure exception-type="Xunit.Sdk.EqualException">
        <message><![CDATA[Assert.Equal() Failure\nExpected: 2\nActual:   40452]]></message>
        <stack-trace><![CDATA[   at System.Runtime.Intrinsics.Tests.Vectors.Vector128Tests.Vector128NIntSumTest()
    at System.Reflection.RuntimeMethodInfo.InvokeWorker(Object obj, BindingFlags invokeAttr, Span`1 parameters)]]></stack-trace>
    </failure>
</test>
<test name="System.Runtime.Intrinsics.Tests.Vectors.Vector128Tests.Vector128NUIntSumTest" type="System.Runtime.Intrinsics.Tests.Vectors.Vector128Tests" method="Vector128NUIntSumTest" time="0.0017315" result="Fail">
    <failure exception-type="Xunit.Sdk.EqualException">
        <message><![CDATA[Assert.Equal() Failure\nExpected: 2\nActual:   40452]]></message>
        <stack-trace><![CDATA[   at System.Runtime.Intrinsics.Tests.Vectors.Vector128Tests.Vector128NUIntSumTest()
    at System.Reflection.RuntimeMethodInfo.InvokeWorker(Object obj, BindingFlags invokeAttr, Span`1 parameters)]]></stack-trace>
    </failure>
</test>

https://dev.azure.com/dnceng/public/_build/results?buildId=1550469&view=ms.vss-test-web.build-test-results-tab&runId=43767104&resultId=112398&paneView=dotnet-dnceng.dnceng-anon-build-release-tasks.helix-anon-test-information-tab

@steveisok @akoeplinger

[ghost]

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Issue Details

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``` ``` https://dev.azure.com/dnceng/public/_build/results?buildId=1550469&view=ms.vss-test-web.build-test-results-tab&runId=43767104&resultId=112398&paneView=dotnet-dnceng.dnceng-anon-build-release-tasks.helix-anon-test-information-tab @steveisok @akoeplinger

Author:	MaximLipnin
Assignees:	-
Labels:	`area-System.Runtime.Intrinsics`, `untriaged`
Milestone:	-

[ghost]

Tagging subscribers to 'os-tvos': @steveisok, @akoeplinger See info in area-owners.md if you want to be subscribed.

Issue Details

---

``` ``` https://dev.azure.com/dnceng/public/_build/results?buildId=1550469&view=ms.vss-test-web.build-test-results-tab&runId=43767104&resultId=112398&paneView=dotnet-dnceng.dnceng-anon-build-release-tasks.helix-anon-test-information-tab @steveisok @akoeplinger

Author:	MaximLipnin
Assignees:	-
Labels:	`area-System.Runtime.Intrinsics`, `untriaged`, `os-tvos`
Milestone:	-

[danmoseley]

@tannergooding

[steveisok]

fyi - tvOS arm64 is our device run.

[steveisok]

@vargaz do you think this is going to work as expected at all on the device?

[danmoseley]

I'm curious about the expected VectorNN story on devices and WASM as well.

[imhameed]

@vargaz do you think this is going to work as expected at all on the device?

I'm curious about the expected VectorNN story on devices

NEON is a part of ARMv8-A so Vector64/Vector128 should be fully supported on arm64 tvOS devices. These tests all passed on arm64 Linux hardware on CI, when the LLVM AOT and LLVM FullAOT lanes were still enabled per-PR. Additionally they passed when I ran them by hand last year on an arm64 Linux machine and on an arm64 Linux VM running on an M1 mac. I have an Apple TV device on hand so I can look into this.

No idea about Wasm though.

[tannergooding]

NEON is a part of ARMv8-A so Vector64/Vector128 should be fully supported on arm64 tvOS devices

Just noting that these APIs in particular are new and have software fallbacks. They won't be accelerated on Mono yet and so the software fallback is what's likely failing here.

The software fallback is: https://source.dot.net/#System.Private.CoreLib/Vector128.cs,f8444b31977d1b83:

[Intrinsic]
public static T Sum<T>(Vector128<T> vector)
    where T : struct
{
    T sum = default;

    for (int index = 0; index < Vector128<T>.Count; index++)
    {
        sum = Scalar<T>.Add(sum, vector.GetElementUnsafe(index));
    }

    return sum;
}

The Scalar<T>.Add method is ultimately going to be doing:

// ...
else if (typeof(T) == typeof(nint))
{
    return (T)(object)((nint)(object)left + (nint)(object)right);
}
else if (typeof(T) == typeof(nuint))
{
    return (T)(object)((nuint)(object)left + (nuint)(object)right);
}
// ...

And GetElementUnsafe is doing:

[MethodImpl(MethodImplOptions.AggressiveInlining)]
internal static T GetElementUnsafe<T>(in this Vector128<T> vector, int index)
    where T : struct
{
    Debug.Assert((index >= 0) && (index < Vector128<T>.Count));
    return Unsafe.Add(ref Unsafe.As<Vector128<T>, T>(ref Unsafe.AsRef(in vector)), index);
}

Also noting however that this is the "safe" fallback implementation used by Vector<T> which has been running and passing for several months now.

[vargaz]

There is another set of test failures on tvos which appears related: https://github.com/dotnet/runtime/issues/61920