为什么 lambda 比 IL 注入的动态方法更快

我刚刚构建了动态方法 - 见下文（感谢SO用户）。看起来 Func 是作为动态方法创建的，IL 注入比 lambda 慢 2 倍。

有谁知道为什么？

（编辑：这是在VS2010中作为x64版本构建的。请从控制台运行它，而不是从Visual Studio F5内部运行它。

class Program
{
    static void Main(string[] args)
    {
        var mul1 = IL_EmbedConst(5);
        var res = mul1(4);
        Console.WriteLine(res);
        var mul2 = EmbedConstFunc(5);
        res = mul2(4);
        Console.WriteLine(res);
        double d, acc = 0;
        Stopwatch sw = new Stopwatch();
        for (int k = 0; k < 10; k++)
        {
            long time1;
            sw.Restart();
            for (int i = 0; i < 10000000; i++)
            {
                d = mul2(i);
                acc += d;
            }
            sw.Stop();
            time1 = sw.ElapsedMilliseconds;
            sw.Restart();
            for (int i = 0; i < 10000000; i++)
            {
                d = mul1(i);
                acc += d;
            }
            sw.Stop();
            Console.WriteLine("{0,6} {1,6}", time1, sw.ElapsedMilliseconds);
        }
        Console.WriteLine("'n{0}...'n", acc);
        Console.ReadLine();
    }
    static Func<int, int> IL_EmbedConst(int b)
    {
        var method = new DynamicMethod("EmbedConst", typeof(int), new[] { typeof(int) } );
        var il = method.GetILGenerator();
        il.Emit(OpCodes.Ldarg_0);
        il.Emit(OpCodes.Ldc_I4, b);
        il.Emit(OpCodes.Mul);
        il.Emit(OpCodes.Ret);
        return (Func<int, int>)method.CreateDelegate(typeof(Func<int, int>));
    }
    static Func<int, int> EmbedConstFunc(int b)
    {
        return a => a * b;
    }
}

这是输出（适用于 i7 920）

20
20
25     51
25     51
24     51
24     51
24     51
25     51
25     51
25     51
24     51
24     51
4.9999995E+15...

====

========================================================================================编辑 编辑

编辑

编辑

这是 dhtorpe 是正确的证明 - 更复杂的 lambda 将失去其优势。代码来证明这一点（这表明 Lambda 在 IL 注入方面具有完全相同的性能）：

class Program
{
    static void Main(string[] args)
    {
        var mul1 = IL_EmbedConst(5);
        double res = mul1(4,6);
        Console.WriteLine(res);
        var mul2 = EmbedConstFunc(5);
        res = mul2(4,6);
        Console.WriteLine(res);
        double d, acc = 0;
        Stopwatch sw = new Stopwatch();
        for (int k = 0; k < 10; k++)
        {
            long time1;
            sw.Restart();
            for (int i = 0; i < 10000000; i++)
            {
                d = mul2(i, i+1);
                acc += d;
            }
            sw.Stop();
            time1 = sw.ElapsedMilliseconds;
            sw.Restart();
            for (int i = 0; i < 10000000; i++)
            {
                d = mul1(i, i + 1);
                acc += d;
            }
            sw.Stop();
            Console.WriteLine("{0,6} {1,6}", time1, sw.ElapsedMilliseconds);
        }
        Console.WriteLine("'n{0}...'n", acc);
        Console.ReadLine();
    }
    static Func<int, int, double> IL_EmbedConst(int b)
    {
        var method = new DynamicMethod("EmbedConstIL", typeof(double), new[] { typeof(int), typeof(int) });
        var log = typeof(Math).GetMethod("Log", new Type[] { typeof(double) });
        var il = method.GetILGenerator();
        il.Emit(OpCodes.Ldarg_0);
        il.Emit(OpCodes.Ldc_I4, b);
        il.Emit(OpCodes.Mul);
        il.Emit(OpCodes.Conv_R8);
        il.Emit(OpCodes.Ldarg_1);
        il.Emit(OpCodes.Ldc_I4, b);
        il.Emit(OpCodes.Mul);
        il.Emit(OpCodes.Conv_R8);
        il.Emit(OpCodes.Call, log);
        il.Emit(OpCodes.Sub);
        il.Emit(OpCodes.Ret);
        return (Func<int, int, double>)method.CreateDelegate(typeof(Func<int, int, double>));
    }
    static Func<int, int, double> EmbedConstFunc(int b)
    {
        return (a, z) => a * b - Math.Log(z * b);
    }
} 

    static Func<int, int> EmbedConstFunc2(int b)
    {
        return a => a * 5;
    }