Computer-Architecture/gcd.asm at main · rithiksachdeva/Computer-Architecture · GitHub

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# gcd.asm — Greatest common divisor for unsigned inputs (RV32I, RARS).
# In: a0/x10, a1/x11. Out: a0 = gcd, or -1 if either input is 0.

.globl gcd

gcd:
	addi sp, sp, -4
	sw ra, 0(sp)

	beqz x10, invalid
	beqz x11, invalid
	beq x10, x11, equal
	blt x10, x11, x10smaller
	blt x11, x10, x11smaller

x10smaller:
	li t0, 1
	mv t2, x10
loop_head1:
	bge t0, t2, loop_end1
	rem t3, x11, t0
	beqz t3, update1
	j noupdate1
update1:
	mv t4, t0
	addi t0, t0, 1
	j loop_head1
noupdate1:
	addi t0, t0, 1
	j loop_head1
loop_end1:
	j print

x11smaller:
	li t0, 1
	mv t2, x11
loop_head2:
	bge t0, t2, loop_end2
	rem t3, x10, t0
	beqz t3, update2
	j noupdate2
update2:
	mv t4, t0
	addi t0, t0, 1
	j loop_head2
noupdate2:
	addi t0, t0, 1
	j loop_head2
loop_end2:
	j print

print:
	mv a0, t4
	j exit
equal:
	mv a0, a1
	j exit
invalid:
	li a0, -1
exit:
	lw ra, 0(sp)
	addi sp, sp, 4
	ret