。while循环的.NET 2.0 IL优化

Question

我一直在读书Pro Asynchronous Programming With .NET，其中第一个代码示例演示了当涉及线程循环时，编译器在.NET 2.0 Framework上进行的优化。

代码如下：

class Program
{
    static void Main(string[] args)
    {
        AsyncSygnal h = new AsyncSygnal();
        while (!h.Terminate) ;
    }

    class AsyncSygnal
    {
        public bool Terminate;

        public AsyncSygnal()
        {
            Thread monitorThread = new Thread(new ThreadStart(MonitorNetwork));
            monitorThread.Start();
        }

        private void MonitorNetwork()
        {
            Thread.Sleep(3000);
            Terminate = true;
        }
    }
}

在书中指出，release构建上的JIT编译器将check移出while循环之外。对于debug buid来说，它工作正常

这怎么可能？

用于调试的IL：

.method private hidebysig static void  Main(string[] args) cil managed
{
  .entrypoint
  // Code size       24 (0x18)
  .maxstack  2
  .locals init ([0] class Program/AsyncSygnal h,
           [1] bool V_1)
  IL_0000:  nop
  IL_0001:  newobj     instance void Program/AsyncSygnal::.ctor()
  IL_0006:  stloc.0
  IL_0007:  br.s       IL_000a
  IL_0009:  nop
  IL_000a:  ldloc.0
  IL_000b:  ldfld      bool Program/AsyncSygnal::Terminate
  IL_0010:  ldc.i4.0
  IL_0011:  ceq
  IL_0013:  stloc.1
  IL_0014:  ldloc.1
  IL_0015:  brtrue.s   IL_0009
  IL_0017:  ret
} // end of method Program::Main

要发布的IL：

.method private hidebysig static void  Main(string[] args) cil managed
{
  .entrypoint
  // Code size       15 (0xf)
  .maxstack  1
  .locals init ([0] class Program/AsyncSygnal h)
  IL_0000:  newobj     instance void Program/AsyncSygnal::.ctor()
  IL_0005:  stloc.0
  IL_0006:  ldloc.0
  IL_0007:  ldfld      bool Program/AsyncSygnal::Terminate
  IL_000c:  brfalse.s  IL_0006
  IL_000e:  ret
} // end of method Program::Main
我想我真正要了解的是我试图了解所输出的IL。

[我一直在阅读Pro .NET异步编程，其中第一个代码示例演示了当线程为循环时，编译器在.NET 2.0 Framework上进行的优化...

Answer 1

让我们举个简单的例子：