3 .type add_digits, @function
7 # Add two arrays of 64 bit digits, with carry, modifying the first argument
8 # Address at first argument %rdi is array to add and modify
9 # Address at second %rsi will be added (not modified)
10 # Third argument is counter of number of digits
11 # Result in %rax is the final result in the carry flag
12 # Exploits the fact that inc and dec do not affect the carry flag
16 movq (%rsi), %rax # Temporarily store digit from second array
17 adcq %rax, (%rdi) # Add digits in second and first array, store in first
18 dec %rdx # Decrement counter
19 jz end_loop # We are done
21 # Move to next element in the first array
23 # Move to next element in the second array