CLR throws InvalidProgramException when a class contains a single static Vector<byte> field

[cesarblum]

Happens on full CLR only.

Repro:

using System.Numerics;

namespace VectorRepro
{
    public class Program
    {
        static Vector<byte> _vector = new Vector<byte>(42);
        //static Vector<byte> _vector2 = new Vector<byte>(43);

        public static void Main(string[] args)
        {
        }
    }
}

Error:

Unhandled Exception: System.TypeInitializationException: The type initializer for 'VectorRepro.Program' threw an exception. ---> System.InvalidProgramException: Common Language Runtime detected an invalid program.
   at VectorRepro.Program..cctor()
   --- End of inner exception stack trace ---
   at VectorRepro.Program.Main(String[] args)

If you uncomment the second static field, no error is thrown.

Other remarks:

• Only seems to happen with byte.
• Also repros if you have multiple static Vector<byte>s in a class and add a new class containing a single one. That's how we actually found it: ForChunkedEncoding vector as static rather than instance aspnet/KestrelHttpServer#874

[cesarblum]

I'm using System.Numerics.Vectors 4.1.0. Kestrel uses 4.1.1-*.

[cesarblum]

Verified on .NET 4.5.1 and 4.6.

[benaadams]

/cc @CarolEidt

[halter73]

This only seems to happen if Vector.IsHardwareAccelerated == True

[CarolEidt]

This appears to be AVX-related. I can't repro it on my non-AVX2 system, and if I set COMPlus_EnableAVX=0 on the AVX2 machine, the problem goes away. I will have a look at this.

[CarolEidt]

It would be great to have a Connect bug filed for this (http://connect.microsoft.com/).
It is indeed AVX-related. The method triggers Compiler::compQuirkForPPP() which works around a bug that was not exposed by jit64.It requires a method that has exactly two locals (which includes compiler temps, which is what is created in this case - and if you uncomment the second static, you get another), one of which is the temp local created for outgoing args (so there has to be a call). It's somewhat related to CoreClr Issue 5116 because if the constructor was recognized as an intrinsic there would not be an outgoing arg space.
It doesn't repro in the coreclr sources because we now re-type the SIMD locals in the importer, so it doesn't match the TYP_STRUCT condition in the quirk.

[joshfree]

@CarolEidt here's a connect bug for .NET 4.6 @ https://connect.microsoft.com/VisualStudio/feedback/details/2751596

You have to click Details to get the actual repro and exception.

[CarolEidt]

This has been fixed in coreclr and will be fixed in a future release of the desktop CLR. There are two workarounds:

• The first is to set COMPlus_EnableAVX=0.
• The second is to declare at least one additional local variable, as is done in this example