assemblies - CLR 4.0 内联策略？ (可能是 MethodImplOptions.NoInlining 的错误)

Question

我在方法内联(交叉汇编内联)中测试了一些新的 CLR 4.0 行为并发现了一些结果:

程序集类库.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()

所以问题是:

• 为什么 JIT 不内联 Foo和 Bar调用为 Baz做？它们小于 32 字节的 IL，非常适合内联。
• 为什么 JIT 内联调用 Bob和 SomeSecurityCriticalMethod 的内部调用标有 [MethodImpl(MethodImplOptions.NoInlining)]属性？
• 为什么 GetExecutingAssembly当被内联调用时返回有效程序集 Baz和 SomeSecurityCriticalMethod方法？我期望它执行堆栈遍历以检测正在执行的程序集，但堆栈将仅包含 Program.Main()没有调用 ClassLib 的方法组装，到ConsoleApp应该归还。

Answer 1

CLR 4.0 对大多数事物都有 ETW 事件，这里是 Jit 的 ETW 跟踪应该给出 MethodJitInliningFailed 原因和 here就是你查看trace信息的方式