# Simple example of functions in ASM, following System V ABI
# and C calling convention

# Everything is stored in registers, so, we have nothing in data section

####################
#		   #
# Function power() #
#		   #
####################

# Remember the return address (where the program should keep executing after
# function return), is also pushed into the stack by the 'call' command.

# Remember, in x86_64 architecture, the Stack grows 'downwards', so, every time
# we want to look back in the stack, we need to add to the current stack
# pointer, other than subtract.

# Ex:
# 56	<- stack 'bottom'
# 48	pushq
# 40	pushq
# 32	<- %rsp (top of the stack)

.type power, @function
power:
	pushq %rbp
	movq %rsp, %rbp
	movq 16(%rbp), %rcx		# Holds the Base number. 16 because:
					# Current %rsp (pushq %rbp) plus the
					# implicit return address pushed by
					# the call command

	movq 24(%rbp), %rbx		# Holds the power (pushed first before
					# function call
	movq %rcx, %rax

loop:
	cmpq $1, %rbx
	je return
	imul %rcx, %rax
	decq %rbx
	jmp loop

return:
	movq %rbp, %rsp
	popq %rbp
	ret