不同的传参和返回值形式在汇编上的差异

从汇编级别了解高级语言的执行过程，下面的汇编代码都是VS的反汇编代码，对比可以看出不同的执行方式在汇编上的差异，现在从最简单的开始。

1：先考察传值和传引用在汇编上的差异。

 

A：简单类型

int show(int m)   //此处int show(int& m) 
{
	int n = m*5;
	return n;
}


int _tmain(int argc, _TCHAR* argv[])
{
	int n = 90;
	int result = 0;
	result = show(n);
	result = result *4;
	int j = 0;
	cin >> j;
	return 0;
}

 

 生成的汇编代码

 

	int n = 90;
00343D5E  mov         dword ptr [n],5Ah  
	int result = 0;
00343D65  mov         dword ptr [result],0  
	result = show(n);
00343D6C  mov         eax,dword ptr [n]  
	result = show(n);//参数压栈
00343D6F  push        eax  
00343D70  call        show (0341460h)  //此处是地址
00343D75  add         esp,4  
00343D78  mov         dword ptr [result],eax  
	result = result *4;
00343D7B  mov         eax,dword ptr [result]  
00343D7E  shl         eax,2  
00343D81  mov         dword ptr [result],eax  
	int j = 0;
00343D84  mov         dword ptr [j],0  
	cin >> j;
00343D8B  mov         esi,esp  
00343D8D  lea         eax,[j]  
00343D90  push        eax  
00343D91  mov         ecx,dword ptr ds:[351378h]  
00343D97  call        dword ptr ds:[351374h]  
00343D9D  cmp         esi,esp  
00343D9F  call        __RTC_CheckEsp (0341311h)  
	return 0;
00343DA4  xor         eax,eax  

 int show(int m)

 

{
	int n = m*5;
00343D1E  mov         eax,dword ptr [m]  
00343D21  imul        eax,eax,5  
00343D24  mov         dword ptr [n],eax  
	return n;
00343D27  mov         eax,dword ptr [n]  //返回值要到Register中？
}

 

传引用：

 

001C3D5E  mov         dword ptr [n],5Ah  
	int result = 0;
001C3D65  mov         dword ptr [result],0  
	result = show(n);
001C3D6C  lea         eax,[n]  
	result = show(n);
001C3D6F  push        eax  
001C3D70  call        show (01C1465h)  
001C3D75  add         esp,4  
001C3D78  mov         dword ptr [result],eax  
	result = result *4;
001C3D7B  mov         eax,dword ptr [result]  
001C3D7E  shl         eax,2  
001C3D81  mov         dword ptr [result],eax  
	int j = 0;
001C3D84  mov         dword ptr [j],0  
	cin >> j;

  

int n = m*5;
001C3D1E  mov         eax,dword ptr [m]  
001C3D21  mov         ecx,dword ptr [eax]  
001C3D23  imul        ecx,ecx,5  
001C3D26  mov         dword ptr [n],ecx  
	return n;
001C3D29  mov         eax,dword ptr [n]  
}