我正在玩Reflection.Emit,并发现了鲜为人知的EmitCalli
。我很好奇,想知道它是否与常规方法调用有所不同,因此我编写了下面的代码:
using System;
using System.Diagnostics;
using System.Reflection.Emit;
using System.Runtime.InteropServices;
using System.Security;
[SuppressUnmanagedCodeSecurity]
static class Program
{
const long COUNT = 1 << 22;
static readonly byte[] multiply = IntPtr.Size == sizeof(int) ?
new byte[] { 0x8B, 0x44, 0x24, 0x04, 0x0F, 0xAF, 0x44, 0x24, 0x08, 0xC3 }
: new byte[] { 0x0f, 0xaf, 0xca, 0x8b, 0xc1, 0xc3 };
static void Main()
{
var handle = GCHandle.Alloc(multiply, GCHandleType.Pinned);
try
{
//Make the native method executable
uint old;
VirtualProtect(handle.AddrOfPinnedObject(),
(IntPtr)multiply.Length, 0x40, out old);
var mulDelegate = (BinaryOp)Marshal.GetDelegateForFunctionPointer(
handle.AddrOfPinnedObject(), typeof(BinaryOp));
var T = typeof(uint); //To avoid redundant typing
//Generate the method
var method = new DynamicMethod("Mul", T,
new Type[] { T, T }, T.Module);
var gen = method.GetILGenerator();
gen.Emit(OpCodes.Ldarg_0);
gen.Emit(OpCodes.Ldarg_1);
gen.Emit(OpCodes.Ldc_I8, (long)handle.AddrOfPinnedObject());
gen.Emit(OpCodes.Conv_I);
gen.EmitCalli(OpCodes.Calli, CallingConvention.StdCall,
T, new Type[] { T, T });
gen.Emit(OpCodes.Ret);
var mulCalli = (BinaryOp)method.CreateDelegate(typeof(BinaryOp));
var sw = Stopwatch.StartNew();
for (int i = 0; i < COUNT; i++) { mulDelegate(2, 3); }
Console.WriteLine("Delegate: {0:N0}", sw.ElapsedMilliseconds);
sw.Reset();
sw.Start();
for (int i = 0; i < COUNT; i++) { mulCalli(2, 3); }
Console.WriteLine("Calli: {0:N0}", sw.ElapsedMilliseconds);
}
finally { handle.Free(); }
}
delegate uint BinaryOp(uint a, uint b);
[DllImport("kernel32.dll", SetLastError = true)]
static extern bool VirtualProtect(
IntPtr address, IntPtr size, uint protect, out uint oldProtect);
}
我在x86模式和x64模式下运行了代码。结果呢?
32位: - 委托版本:994 - Calli版本:46
64位: - 委托版本:326 - Calli版本:83
现在问题显而易见,为什么速度差别如此之大呢?
更新: 我也创建了一个64位的P/Invoke版本:
- 委托版本:284 - Calli版本:77 - P/Invoke版本:31
显然,P/Invoke更快... 这是我的基准测试有问题,还是有我不理解的东西?(顺便说一句,我处于发布模式。)