JIT: Bad result with vector argument

[jakobbotsch]

// Generated by Fuzzlyn v2.5 on 2025-03-13 04:54:06
// Run on X64 Linux
// Seed: 15128240988293741626-vectort,vector128,vector256,x86aes,x86avx,x86avx2,x86bmi1,x86bmi1x64,x86bmi2,x86bmi2x64,x86fma,x86lzcnt,x86lzcntx64,x86pclmulqdq,x86popcnt,x86popcntx64,x86sse,x86ssex64,x86sse2,x86sse2x64,x86sse3,x86sse41,x86sse41x64,x86sse42,x86sse42x64,x86ssse3,x86x86base
// Reduced from 188.7 KiB to 0.8 KiB in 00:01:09
// Debug: Outputs 0
// Release: Outputs 1
using System;
using System.Numerics;
using System.Runtime.Intrinsics;
using System.Runtime.Intrinsics.X86;

public struct S0
{
    public uint F0;
    public ushort M7()
    {
        this.F0 = 1;
        Program.s_rt.WriteLine(this.F0);
        return 0;
    }
}

public class Program
{
    public static IRuntime s_rt;
    public static void Main()
    {
        s_rt = new Runtime();
        S0 vr0 = default(S0);
        M4(vr0, Vector256.Create<ushort>(vr0.M7()));
    }

    public static void M4(S0 arg0, Vector256<ushort> arg1)
    {
        s_rt.WriteLine(arg0.F0);
    }
}

public interface IRuntime
{
    void WriteLine<T>(T value);
}

public class Runtime : IRuntime
{
    public void WriteLine<T>(T value) => System.Console.WriteLine(value);
}

Bisected to #112612

cc @dotnet/jit-contrib

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