generic vs non-generic state machine

gistfile1.cs

C# code:

IEnumerable NonGenericEmptyEnumerable()
{
	yield break;
}

IEnumerable<T> GenericEmptyEnumerable<T>()
{
	yield break;
}

IL Code:

IL_0000:  ret         

NonGenericEmptyEnumerable:
IL_0000:  ldc.i4.s    FE 
IL_0002:  newobj      UserQuery+<NonGenericEmptyEnumerable>d__0..ctor
IL_0007:  stloc.0     
IL_0008:  ldloc.0     
IL_0009:  ldarg.0     
IL_000A:  stfld       UserQuery+<NonGenericEmptyEnumerable>d__0.<>4__this
IL_000F:  ldloc.0     
IL_0010:  ret         

GenericEmptyEnumerable:
IL_0000:  ldc.i4.s    FE 
IL_0002:  newobj      18 00 00 0A 
IL_0007:  stloc.0     
IL_0008:  ldloc.0     
IL_0009:  ldarg.0     
IL_000A:  stfld       19 00 00 0A 
IL_000F:  ldloc.0     
IL_0010:  ret         

<NonGenericEmptyEnumerable>d__0.System.Collections.Generic.IEnumerable<System.Object>.GetEnumerator:
IL_0000:  call        System.Environment.get_CurrentManagedThreadId
IL_0005:  ldarg.0     
IL_0006:  ldfld       UserQuery+<NonGenericEmptyEnumerable>d__0.<>l__initialThreadId
IL_000B:  bne.un.s    IL_0022
IL_000D:  ldarg.0     
IL_000E:  ldfld       UserQuery+<NonGenericEmptyEnumerable>d__0.<>1__state
IL_0013:  ldc.i4.s    FE 
IL_0015:  bne.un.s    IL_0022
IL_0017:  ldarg.0     
IL_0018:  ldc.i4.0    
IL_0019:  stfld       UserQuery+<NonGenericEmptyEnumerable>d__0.<>1__state
IL_001E:  ldarg.0     
IL_001F:  stloc.0     
IL_0020:  br.s        IL_0035
IL_0022:  ldc.i4.0    
IL_0023:  newobj      UserQuery+<NonGenericEmptyEnumerable>d__0..ctor
IL_0028:  stloc.0     
IL_0029:  ldloc.0     
IL_002A:  ldarg.0     
IL_002B:  ldfld       UserQuery+<NonGenericEmptyEnumerable>d__0.<>4__this
IL_0030:  stfld       UserQuery+<NonGenericEmptyEnumerable>d__0.<>4__this
IL_0035:  ldloc.0     
IL_0036:  ret         

<NonGenericEmptyEnumerable>d__0.System.Collections.IEnumerable.GetEnumerator:
IL_0000:  ldarg.0     
IL_0001:  call        UserQuery+<NonGenericEmptyEnumerable>d__0.System.Collections.Generic.IEnumerable<System.Object>.GetEnumerator
IL_0006:  ret         

<NonGenericEmptyEnumerable>d__0.MoveNext:
IL_0000:  ldarg.0     
IL_0001:  ldfld       UserQuery+<NonGenericEmptyEnumerable>d__0.<>1__state
IL_0006:  stloc.0     // CS$0$0000
IL_0007:  ldloc.0     // CS$0$0000
IL_0008:  ldc.i4.0    
IL_0009:  bne.un.s    IL_0012
IL_000B:  ldarg.0     
IL_000C:  ldc.i4.m1   
IL_000D:  stfld       UserQuery+<NonGenericEmptyEnumerable>d__0.<>1__state
IL_0012:  ldc.i4.0    
IL_0013:  ret         

<NonGenericEmptyEnumerable>d__0.System.Collections.Generic.IEnumerator<System.Object>.get_Current:
IL_0000:  ldarg.0     
IL_0001:  ldfld       UserQuery+<NonGenericEmptyEnumerable>d__0.<>2__current
IL_0006:  ret         

<NonGenericEmptyEnumerable>d__0.System.Collections.IEnumerator.Reset:
IL_0000:  newobj      System.NotSupportedException..ctor
IL_0005:  throw       

<NonGenericEmptyEnumerable>d__0.System.IDisposable.Dispose:
IL_0000:  ret         

<NonGenericEmptyEnumerable>d__0.System.Collections.IEnumerator.get_Current:
IL_0000:  ldarg.0     
IL_0001:  ldfld       UserQuery+<NonGenericEmptyEnumerable>d__0.<>2__current
IL_0006:  ret         

<NonGenericEmptyEnumerable>d__0..ctor:
IL_0000:  ldarg.0     
IL_0001:  call        System.Object..ctor
IL_0006:  ldarg.0     
IL_0007:  ldarg.1     
IL_0008:  stfld       UserQuery+<NonGenericEmptyEnumerable>d__0.<>1__state
IL_000D:  ldarg.0     
IL_000E:  call        System.Environment.get_CurrentManagedThreadId
IL_0013:  stfld       UserQuery+<NonGenericEmptyEnumerable>d__0.<>l__initialThreadId
IL_0018:  ret         

<GenericEmptyEnumerable>d__3`1.System.Collections.Generic.IEnumerable<T>.GetEnumerator:
IL_0000:  call        System.Environment.get_CurrentManagedThreadId
IL_0005:  ldarg.0     
IL_0006:  ldfld       12 00 00 0A 
IL_000B:  bne.un.s    IL_0022
IL_000D:  ldarg.0     
IL_000E:  ldfld       13 00 00 0A 
IL_0013:  ldc.i4.s    FE 
IL_0015:  bne.un.s    IL_0022
IL_0017:  ldarg.0     
IL_0018:  ldc.i4.0    
IL_0019:  stfld       13 00 00 0A 
IL_001E:  ldarg.0     
IL_001F:  stloc.0     
IL_0020:  br.s        IL_0035
IL_0022:  ldc.i4.0    
IL_0023:  newobj      14 00 00 0A 
IL_0028:  stloc.0     
IL_0029:  ldloc.0     
IL_002A:  ldarg.0     
IL_002B:  ldfld       15 00 00 0A 
IL_0030:  stfld       15 00 00 0A 
IL_0035:  ldloc.0     
IL_0036:  ret         

<GenericEmptyEnumerable>d__3`1.System.Collections.IEnumerable.GetEnumerator:
IL_0000:  ldarg.0     
IL_0001:  call        16 00 00 0A 
IL_0006:  ret         

<GenericEmptyEnumerable>d__3`1.MoveNext:
IL_0000:  ldarg.0     
IL_0001:  ldfld       13 00 00 0A 
IL_0006:  stloc.0     // CS$0$0000
IL_0007:  ldloc.0     // CS$0$0000
IL_0008:  ldc.i4.0    
IL_0009:  bne.un.s    IL_0012
IL_000B:  ldarg.0     
IL_000C:  ldc.i4.m1   
IL_000D:  stfld       13 00 00 0A 
IL_0012:  ldc.i4.0    
IL_0013:  ret         

<GenericEmptyEnumerable>d__3`1.System.Collections.Generic.IEnumerator<T>.get_Current:
IL_0000:  ldarg.0     
IL_0001:  ldfld       17 00 00 0A 
IL_0006:  ret         

<GenericEmptyEnumerable>d__3`1.System.Collections.IEnumerator.Reset:
IL_0000:  newobj      System.NotSupportedException..ctor
IL_0005:  throw       

<GenericEmptyEnumerable>d__3`1.System.IDisposable.Dispose:
IL_0000:  ret         

<GenericEmptyEnumerable>d__3`1.System.Collections.IEnumerator.get_Current:
IL_0000:  ldarg.0     
IL_0001:  ldfld       17 00 00 0A 
IL_0006:  box         06 00 00 1B 
IL_000B:  ret         

<GenericEmptyEnumerable>d__3`1..ctor:
IL_0000:  ldarg.0     
IL_0001:  call        System.Object..ctor
IL_0006:  ldarg.0     
IL_0007:  ldarg.1     
IL_0008:  stfld       13 00 00 0A 
IL_000D:  ldarg.0     
IL_000E:  call        System.Environment.get_CurrentManagedThreadId
IL_0013:  stfld       12 00 00 0A 
IL_0018:  ret