c# 是否可以使用FNSTCW FPUControlWord FNINIT

是的，C#可以使用FNSTCW和FNINIT指令。FNSTCW指令用于将当前的FPU控制字存储到指定的内存位置中，而FNINIT指令用于将FPU初始化为其默认状态。在C#中，可以使用汇编语言嵌入来使用这些指令。以下是一个使用FNSTCW和FNINIT指令的示例：

using System;
using System.Runtime.InteropServices;

class Program
{
    [DllImport("kernel32.dll")]
    public static extern void GetSystemInfo(ref SYSTEM_INFO lpSysInfo);

    [StructLayout(LayoutKind.Sequential)]
    public struct SYSTEM_INFO
    {
        public ushort wProcessorArchitecture;
        public ushort wReserved;
        public uint dwPageSize;
        public IntPtr lpMinimumApplicationAddress;
        public IntPtr lpMaximumApplicationAddress;
        public IntPtr dwActiveProcessorMask;
        public uint dwNumberOfProcessors;
        public uint dwProcessorType;
        public uint dwAllocationGranularity;
        public ushort wProcessorLevel;
        public ushort wProcessorRevision;
    }

    [DllImport("msvcrt.dll", CallingConvention = CallingConvention.Cdecl)]
    public static extern void _fpreset();

    [DllImport("msvcrt.dll", CallingConvention = CallingConvention.Cdecl)]
    public static extern ushort _control87(ushort newcw, ushort mask);

    static void Main(string[] args)
    {
        // 获取系统信息
        SYSTEM_INFO sysInfo = new SYSTEM_INFO();
        GetSystemInfo(ref sysInfo);

        // 打印处理器架构
        Console.WriteLine("Processor Architecture: {0}", sysInfo.wProcessorArchitecture);

        // 存储当前的FPU控制字
        ushort controlWord = 0;
        byte[] controlBytes = new byte[2];
        unsafe
        {
            fixed (byte* p = controlBytes)
            {
                ushort* controlPtr = (ushort*)p;
                asm
                {
                    fnstcw [controlPtr]
                }
            }
        }
        controlWord = (ushort)(controlBytes[0] | (controlBytes[1] << 8));

        // 打印当前的FPU控制字
        Console.WriteLine("Current FPU Control Word: 0x{0:X4}", controlWord);

        // 初始化FPU
        _fpreset();
        _control87(0x037F, 0xFFFF);

        // 存储初始化后的FPU控制字
        controlBytes = new byte[2];
        unsafe
        {
            fixed (byte* p = controlBytes)
            {
                ushort* controlPtr = (ushort*)p;
                asm
                {
                    fnstcw [controlPtr]
                }
            }
        }
        controlWord = (ushort)(controlBytes[0] | (controlBytes[1] << 8));

        // 打印初始化后的FPU控制字
        Console.WriteLine("Initialized FPU Control Word: 0x{0:X4}", controlWord);
    }
}