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int main () {
vector<int> a {1 ,2 ,3 ,4} ;
for (int i = 0 ; i < int (a.size ()) ; i++)
cout << a[i] << " " ;
return 0 ;
}
/*
vector<int> a {1 ,2 ,3 ,4} ;
000000013F681042 xor esi,esi
000000013F681044 mov qword ptr [r11-20h],rsi
000000013F681048 lea r8,[r11-38h]
000000013F68104C lea rdx,[r11-48h]
000000013F681050 lea rcx,[r11-30h]
000000013F681054 call std::vector<int,std::allocator<int> >::_Construct<int const * __ptr64> (013F681420h)
000000013F681059 nop
for (int i = 0 ; i < int (a.size ()) ; i++)
000000013F68105A mov rbp,qword ptr [rsp+40h]
000000013F68105F mov rbx,qword ptr [a]
000000013F681064 sub rbp,rbx
000000013F681067 sar rbp,2
000000013F68106B test ebp,ebp
000000013F68106D jle main+0A1h (013F6810A1h)
000000013F68106F mov rdi,rbx
000000013F681072 nop dword ptr [rax]
000000013F681076 nop word ptr [rax+rax]
cout << a[i] << " " ;
000000013F681080 mov edx,dword ptr [rdi]
000000013F681082 mov rcx,qword ptr [__imp_std::cout (013F683088h)]
000000013F681089 call qword ptr [__imp_std::basic_ostream<char,std::char_traits<char> >::operator<< (013F683080h)]
000000013F68108F mov rcx,rax
000000013F681092 call std::operator<<<std::char_traits<char> > (013F681270h)
for (int i = 0 ; i < int (a.size ()) ; i++)
000000013F681097 inc esi
000000013F681099 lea rdi,[rdi+4]
000000013F68109D cmp esi,ebp
000000013F68109F jl main+80h (013F681080h)
return 0 ;
*/
大部分的编译器优化能力都不会太弱,简单的getter,setter都会被内联展开
这种问题不用纠结,大部分代码运行时间不是花费在这上面的