It’s probably:
xorl %ebx, %ebx
This is a common idiom for zeroing a register on x86. This would correspond with i = 0 in the C code.
If you are curious “but why ?” the short answer is that the xor instruction is fewer bytes than mov $0, %ebx. The long answer includes other subtle reasons.
I am leaving out the rest of the exercise since there’s nothing idiosyncratic left.
