Optimization of proposed lambda expression for upcoming DIP

[Michael V. Franklin]

I'm currently testing the optimization for the proposed lowering 
in this upcoming DIP: https://github.com/dlang/DIPs/pull/97

Tested at https://explore.dgnu.org/ (love this tool, by the way) 
64-bit (PC) gdc 7 with -O3 -frelease

/********** Lowering expression to lambda *************/
import core.bitop;

struct S
{
     uint field;

     uint prop() @property
     {
         return field;
     }

     uint prop(uint value) @property
     {
         return field = value;
     }
}

void main()
{
     S s;
     ((auto ref _e1) => _e1.prop(_e1.prop() + 1))(s);

     // prevent compiler from optimizing the whole thing away
     volatileStore(cast(uint*)32, s.field);
}

// OUTPUT
main:
         movq    _Dmain at GOTPCREL(%rip), %rdx
         jmp     _d_run_main at PLT
         movl    (%rdi), %eax
         ret
         movl    %esi, %eax
         movl    %esi, (%rdi)
         ret
_Dmain:
         movl    $1, 32
         xorl    %eax, %eax
         ret
uint example.main().__lambda1!(example.S).__lambda1(ref 
example.S):
         movl    (%rdi), %eax
         addl    $1, %eax
         movl    %eax, (%rdi)
         ret

/****** Functionally equivalent code without lowering ***********/
import core.bitop;

struct S
{
     uint field;
}

void main()
{
     S s;
     s.field += 1;

     // prevent compiler from optimizing the whole thing away
     volatileStore(cast(uint*)32, s.field);
}

// OUTPUT
main:
         movq    _Dmain at GOTPCREL(%rip), %rdx
         jmp     _d_run_main at PLT
_Dmain:
         movl    $1, 32
         xorl    %eax, %eax
         ret

-- Analysis --
`_Dmain` is equivalent, as I expected, but what's going on with 
`main`?  Anything to be concerned about?

Mike