JIT: (bug) negating the first operand of a scalar FMA drops the negation from the copied upper lanes #133553

using System;
using System.Runtime.CompilerServices;
using System.Runtime.Intrinsics;
using System.Runtime.Intrinsics.X86;

class Program
{
    [MethodImpl(MethodImplOptions.NoInlining | MethodImplOptions.AggressiveOptimization)]
    static Vector128<float> Test(Vector128<float> a, Vector128<float> b, Vector128<float> c) =>
        Fma.MultiplyAddScalar(-a, b, c);

    static void Main()
    {
        if (!Fma.IsSupported)
            throw new PlatformNotSupportedException("FMA is required.");

        // lane 0 = (-2)*10 + 1; lanes 1..3 are copied from the first operand, which is -a.
        var r = Test(Vector128.Create(2.0f, 3.0f, 4.0f, 5.0f),
                     Vector128.Create(10.0f),
                     Vector128.Create(1.0f));
        Console.WriteLine($"{r.GetElement(0)} {r.GetElement(1)} {r.GetElement(2)} {r.GetElement(3)}");
    }
}