CLR4.0内联策略？(可能是MethodImplOptions.NoInlining的bug )

Question

我在方法内联(交叉组装内联)中测试了一些新的CLR4.0行为，并发现了一些障碍结果：

程序集ClassLib.dll

using System.Diagnostics;
using System;
using System.Reflection;
using System.Security;
using System.Runtime.CompilerServices;

namespace ClassLib
{
  public static class A
  {
    static readonly MethodInfo GetExecuting =
      typeof(Assembly).GetMethod("GetExecutingAssembly");

    public static Assembly Foo(out StackTrace stack) // 13 bytes
    {
      // explicit call to GetExecutingAssembly()
      stack = new StackTrace();
      return Assembly.GetExecutingAssembly();
    }

    public static Assembly Bar(out StackTrace stack) // 25 bytes
    {
      // reflection call to GetExecutingAssembly()
      stack = new StackTrace();
      return (Assembly) GetExecuting.Invoke(null, null);
    }

    public static Assembly Baz(out StackTrace stack) // 9 bytes
    {
      stack = new StackTrace();
      return null;
    }

    public static Assembly Bob(out StackTrace stack) // 13 bytes
    {
      // call of non-inlinable method!
      return SomeSecurityCriticalMethod(out stack);
    }

    [SecurityCritical, MethodImpl(MethodImplOptions.NoInlining)]
    static Assembly SomeSecurityCriticalMethod(out StackTrace stack)
    {
      stack = new StackTrace();
      return Assembly.GetExecutingAssembly();
    }
  }
}

程序集ConsoleApp.exe

using System;
using ClassLib;
using System.Diagnostics;

class Program
{
  static void Main()
  {
    Console.WriteLine("runtime: {0}", Environment.Version);

    StackTrace stack;
    Console.WriteLine("Foo: {0}\n{1}", A.Foo(out stack), stack);
    Console.WriteLine("Bar: {0}\n{1}", A.Bar(out stack), stack);
    Console.WriteLine("Baz: {0}\n{1}", A.Baz(out stack), stack);
    Console.WriteLine("Bob: {0}\n{1}", A.Bob(out stack), stack);
  }
}

结果：

runtime: 4.0.30128.1

Foo: ClassLib, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null
   at ClassLib.A.Foo(StackTrace& stack)
   at Program.Main()

Bar: ClassLib, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null
   at ClassLib.A.Bar(StackTrace& stack)
   at Program.Main()

Baz:
   at Program.Main()

Bob: ClassLib, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null
   at Program.Main()

因此，问题是：

• 为什么JIT不像Foo和Bar那样内联Baz调用？它们小于32字节的IL，是很好的内衬候选。
• 为什么Bob的JIT内联调用和标记为[MethodImpl(MethodImplOptions.NoInlining)]属性的SomeSecurityCriticalMethod内部调用？
• 当内联的GetExecutingAssembly和SomeSecurityCriticalMethod方法调用时，为什么SomeSecurityCriticalMethod返回一个有效的程序集？我希望它执行堆栈遍历来检测正在执行的程序集，但是堆栈将只包含Program.Main()调用，而不包含ClassLib的任何方法，应该返回到ConsoleApp。

Answer 1

CLR4.0在大多数情况下都有ETW事件，下面是Jit的ETW跟踪，它应该给出MethodJitInliningFailed的原因，这里是如何查看跟踪信息的