power_extended.s

# as --32 power_extended.s -o ./bin/power_extended.a && ld -m elf_i386 ./bin/power_extended.a -o ./bin/power_extended && rm ./bin/power_extended.a


.section .data

.section .text

.globl _start

_start:
#push the variables (base and power) on to the stack
pushl $3 # power
pushl $2 # base
call power # returns to eax

addl $8, %esp
pushl %eax # push the result onto the stack

pushl $0 #power
pushl $2 #base
call power
addl $8, %esp
popl %ebx
addl %eax, %ebx

movl $1, %eax
int $0x80

# %ebx - the base
# %ecx - the power
# -4(%ebp) - holds the current result - note that it's a stack pointer
# %eax is used for temp storage

.type power, @function
power:
pushl %ebp
movl %esp, %ebp
subl $4, %esp

movl 8(%ebp), %ebx
movl 12(%ebp), %ecx
movl %ebx, -4(%ebp)

# handle power 0
cmpl $0, %ecx
je power_zero

power_loop_start:
cmpl $1, %ecx
je  end_power
movl -4(%ebp), %eax
imull %ebx, %eax
movl %eax, -4(%ebp)
decl %ecx
jmp power_loop_start

end_power:
movl -4(%ebp), %eax
movl %ebp, %esp
popl %ebp
ret

power_zero:
movl $1, %eax
movl %ebp, %esp
popl %ebp
ret