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# Compute a^b, where %rbx=a and %rcx=b
#
# Result is added to the accumulator (%rax)
.globl _start
.section .text
_start:
movq $2, %rbx # Base
movq $5, %rcx # Exponent
movq $1, %rax # Initialize accumulator, take advantage of the fact
# that anything to the power of 0 is 1.
# We just need to run this once, as decq will set ZF if %rcx reaches
# zero, and the jmp instruction does nothing with the ZF
cmpq $0, %rcx
je complete
mainloop:
# Multiply %rbx by %rax, and stores the result in %rax
# Hence %rax is the accumulator register
mulq %rbx
# loopq instruction is very nice, in a single instruction it does:
# - decrement %rcx - The counter register -
# - compare %rcx to zero
# - Jump to the location specified if after decrementing %rcx is not 0
loopq mainloop
complete:
movq %rax, %rdi
movq $60, %rax
syscall
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