I’m thinking of writing about what I learn about C and C++. Writing allow me to think slowly and properly understand things.
If you think about it, for loop can be done with a while loop. Even do-while can be simulated with a while if you add some duplicate code before.
int main(void) {
int i = 1;
int j = 0;
while (i <= 10) {
j += i;
i++;
}
return j;
}
main:
; save stack pointer
push rbp
mov rbp, rsp
; int i = 1
mov DWORD PTR [rbp-4], 1
; int j = 0
mov DWORD PTR [rbp-8], 0
; go to .L2
jmp .L2
.L3:
; eax = i
mov eax, DWORD PTR [rbp-4]
; j += eax
add DWORD PTR [rbp-8], eax
; i += 1
add DWORD PTR [rbp-4], 1
.L2:
; compare i and 10
cmp DWORD PTR [rbp-4], 10
; if less than or eq jump to .L3
jle .L3
; eax = j
mov eax, DWORD PTR [rbp-8]
; revert stack pointer back to previous value
pop rbp
; return eax
ret
📝
x86-64 gcc 11.2 with -O0