sommaScacchiera.s

.globl main

.data
N: .word 3

M: .word 0, 1, 2, 3, 4, 5, 6, 7, 8

.text
main:
	la $a0, M # a0 = M pointer
	lw $a1, N # a1 = N = 3
	
	jal sommaScacchiera # v0, v1 = sommaSchacchiera(a0, a1)
	
	move $a0, $v0 # a0 = v0
	li $v0, 1 # print int
	syscall
	move $a0, $v1 # a0 = v1
	li $v0, 1 # print int
	syscall
	li $v0, 10 # exit
	syscall
		
# v0,  = sommaScacchiera(a0: pointer, a1: int)
sommaScacchiera:
	# push stack
	subi $sp, $sp, 8
	sw $fp, 4($sp)
	sw $ra, 0($sp)

	jal sommaPari # v0 = sommaPari(a0, a1)
	
	jal sommaDispari # v0 = sommaDispari(a0, a1)
	
	# pop stack
	lw $ra, 0($sp)
	lw $fp, 4($sp)
	addi $sp, $sp, 8
	
	jr $ra

# v0 = sommaPari(a0: pointer, a1: int)
sommaPari:
	# push stack
	subi $sp, $sp, 4
	sw $ra, 0($sp)
	
	# index
	move $t1, $zero # t1 = 0
	
	# result register
	move $v0, $zero # v0 = 0
	
	# evaluate exit condition, t2 = N * N * 4
	mul $t2, $a1, $a1 # lo = a1 * a1 (result gets stored in lo)
	mflo $t2 # t2 = lo
	sll $t2, $t2, 2 # t2 <<= 2, t2 *= 4
	
	# temp var
	move $t4, $zero
	
	loopPari:
		bgt $t1, $t2, exitPari # while t1 < t2
		add $t4, $a0, $t1 # t4 = a0 + t1, M_pointer + index
		lw $t3, 0($t4) # t3 = mem[t4]
		add $v0, $v0, $t3 # v0 += t3
		addi $t1, $t1, 8 # t1 += 8
		j loopPari
		
	exitPari:
		# pop stack
		lw $ra, 0($sp)
		addi $sp, $sp, 4
	
		jr $ra

# v1 = sommaDispari(a0: pointer, a1: int)
sommaDispari:
	# push stack
	subi $sp, $sp, 4
	sw $ra, 0($sp)
	
	# index, t1 = 4
	move $t1, $zero # t1 = zero
	addi $t1, $t1, 4 # t1 += 4
	
	# result register
	move $v1, $zero # v0 = 0
	
	# evaluate exit condition, t2 = N * N * 4
	mul $t2, $a1, $a1 # lo = a1 * a1 (result gets stored in lo)
	mflo $t2 # t2 = lo
	sll $t2, $t2, 2 # t2 <<= 2, t2 *= 4
	
	# temp var
	move $t4, $zero # t4 = 0
	
	loopDispari:
		bgt $t1, $t2, exitDispari # while t1 < t2
		add $t4, $a0, $t1 # t4 = a0 + t1, M_pointer + index
		lw $t3, 0($t4) # t3 = mem[t4]
		add $v1, $v1, $t3 # v1 += t3
		addi $t1, $t1, 8 # t1 += 8, skipping 1 value
		j loopDispari
		
	exitDispari:
		# pop stack
		lw $ra, 0($sp)
		addi $sp, $sp, 4
	
		jr $ra