Coding for loop with an assembler in c++ function - c++

Question

I was always interested in assembler, however so far I didn't have a true chance to confront it in a best way. Now, when I do have some time, I began coding some small programs using assembler in a c++, but that's just small ones, i.e. define x, store it somewhere and so on, so forth. I wanted to implement foor loop in assembler, but I couldn't make it, so I would like to ask if anyone here has ever done with it, would be nice to share here. Example of some function would be
for(i=0;i<10;i++) { std::cout<< "A"; }
Anyone has some idea how to implement this in a assembler?
edit2: ISA x86

Answer 1

Here's the unoptimized output1 of GCC for this code:
void some_function(void);
int main()
{
for (int i = 0; i < 137; ++i) { some_function(); }
}
movl $0, 12(%esp) // i = 0; i is stored at %esp + 12
jmp .L2
.L3:
call some_function // some_function()
addl $1, 12(%esp) // ++i
.L2:
cmpl $136, 12(%esp) // compare i to 136 ...
jle .L3 // ... and repeat loop less-or-equal
movl $0, %eax // return 0
leave // --"--
With optimization -O3, the addition+comparison is turned into subtraction:
pushl %ebx // save %ebx
movl $137, %ebx // set %ebx to 137
// some unrelated parts
.L2:
call some_function // some_function()
subl $1, %ebx // subtract 1 from %ebx
jne .L2 // if not equal to 0, repeat loop
1The generated assembly can be examined by invoking GCC with the -S flag.

Answer 2

Try to rewrite the for loop in C++ using a goto and an if statement and you will have the basics for the assembly version.

Answer 3

You could try the reverse - write the program in C++ or C and look at the dissasembled code:
for ( int i = 0 ; i < 10 ; i++ )
00E714EE mov dword ptr [i],0
00E714F5 jmp wmain+30h (0E71500h)
00E714F7 mov eax,dword ptr [i]
00E714FA add eax,1
00E714FD mov dword ptr [i],eax
00E71500 cmp dword ptr [i],0Ah
00E71504 jge wmain+4Bh (0E7151Bh)
cout << "A";
00E71506 push offset string "A" (0E76800h)
00E7150B mov eax,dword ptr [__imp_std::cout (0E792ECh)]
00E71510 push eax
00E71511 call std::operator<<<std::char_traits<char> > (0E71159h)
00E71516 add esp,8
00E71519 jmp wmain+27h (0E714F7h)
then try to make sense of it.