测试环境：VS2015
内置类型（int举例）：
1 int a=0,i=0;
2 a = i++;
3 a = ++i;
1 int a=0,i=0;
2 00921DAB mov dword ptr [a],0
3 00921DB5 mov dword ptr [i],0
4 a = i++;
5 00921DBF mov eax,dword ptr [i]
6 00921DC5 mov dword ptr [a],eax
7 00921DCB mov ecx,dword ptr [i]
8 00921DD1 add ecx,1
9 00921DD4 mov dword ptr [i],ecx
10 a = ++i;
11 00921DDA mov edx,dword ptr [i]
12 00921DE0 add edx,1
13 00921DE3 mov dword ptr [i],edx
14 00921DE9 mov eax,dword ptr [i]
15 00921DEF mov dword ptr [a],eax
后置++i和i++的+1操作的执行顺序的不同，效率几乎无区别
i++将i的值赋值到eax寄存器中，然后在将eax寄存器的值赋值到变量a所在的内存地址中，然后再讲i的值赋值到ecx，执行ecx+1，加1后再重新对i的赋值为ecx.
++i将i的值赋值到edx寄存器中，然后再将edx直接加1，然后赋值给i,i此时已经+1，固需要利用eax对a的内存进行赋值为i.
非内置类型（举例）：
1 class Test 2 { 3 public: 4 Test() :a(5) {} 5 Test& operator ++() 6 { 7 ++a; 8 return *this; 9 } 10 const Test operator++(int) 11 { 12 Test oldTest = *this; 13 ++a; 14 return oldTest; 15 } 16 private: 17 int a; 18 }; 19 int main(int argc, char *argv[]) 20 { 21 int a=0,i=0; 22 a = i++; 23 a = ++i; 24 Test test; 25 ++test; 26 test++;
27 }
1 Test test;
2 00D81DF5 lea ecx,[test]
3 00D81DFB call Test::Test (0D82050h)
4 ++test;
5 00D81E00 lea ecx,[test]
6 00D81E06 call Test::operator++ (0D82160h)
7 test++;
8 00D81E0B push 0
9 test++;
10 00D81E0D lea ecx,[ebp-19Ch]
11 00D81E13 push ecx
12 00D81E14 lea ecx,[test]
13 00D81E1A call Test::operator++ (0D82130h)
1 Test& operator ++()
2 {
3 00D82160 push ebp
4 00D82161 mov ebp,esp
5 00D82163 push ecx
6 00D82164 mov dword ptr [this],ecx
7 ++a;
8 00D82167 mov eax,dword ptr [this]
9 ++a;
10 00D8216A mov ecx,dword ptr [eax]
11 00D8216C add ecx,1
12 00D8216F mov edx,dword ptr [this]
13 00D82172 mov dword ptr [edx],ecx
14 return *this;
15 00D82174 mov eax,dword ptr [this]
16 }
17 00D82177 mov esp,ebp
18 00D82179 pop ebp
19 00D8217A ret
1 const Test operator++(int)
2 {
3 00D82130 push ebp
4 00D82131 mov ebp,esp
5 00D82133 sub esp,8
6 00D82136 mov dword ptr [this],ecx
7 Test oldTest = *this;
8 00D82139 mov eax,dword ptr [this]
9 Test oldTest = *this;
10 00D8213C mov ecx,dword ptr [eax]
11 00D8213E mov dword ptr [oldTest],ecx
12 ++a;
13 00D82141 mov edx,dword ptr [this]
14 00D82144 mov eax,dword ptr [edx]
15 00D82146 add eax,1
16 00D82149 mov ecx,dword ptr [this]
17 00D8214C mov dword ptr [ecx],eax
18 return oldTest;
19 00D8214E mov edx,dword ptr [ebp+8]
20 00D82151 mov eax,dword ptr [oldTest]
21 00D82154 mov dword ptr [edx],eax
22 00D82156 mov eax,dword ptr [ebp+8]
23 }
24 00D82159 mov esp,ebp
25 00D8215B pop ebp
26 00D8215C ret 8
对于非内置类型，显然后置++要需要更多的效率开销。