Updated lab03_solution.asm to conduct nested stack ops

tests/lab03_solution-gzz.asm

@@ -0,0 +1,106 @@
+# Calculate the product of data elements of a list
+# for MYΥ-505 - Computer Architecture
+# Department of Computer Engineering, University of Ioannina
+# Aris Efthymiou
+
+       .globl mulproc, listProd # declare the label main as global. 
+
+        ###############################################################################
+        # Data input.
+        ###############################################################################
+       .data
+# 1st item - head of the list!
+n1_d: .word 1
+n1_n: .word n2_d  # point to (beginning of) n2
+
+# 3rd item
+n3_d: .word 3
+n3_n: .word n4_d
+
+# 2nd item
+n2_d: .word 2
+n2_n: .word n3_d
+
+# 5th item
+n5_d: .word 5
+n5_n: .word 0 # This is the last iterm in the list
+
+# 4th item
+n4_d: .word 4
+n4_n: .word n5_d
+
+# Alternative head of list. Value 0 to test mult by 0
+na_d: .word 0
+na_n: .word n2_d  # point to (beginning of) n2
+
+        .text 
+        # These are for providing input and testing, don't change in your
+        #  final submission
+        la    $a0, n1_d
+        jal   listProd
+        addu  $s0, $v0, $zero   # Move the result to s0
+        # Try it with a null pointer
+        addu  $a0, $zero, $zero
+        jal   listProd
+        addu  $s1, $v0, $zero   # Move the result to s1
+        # Try it with 1 item list
+        la    $a0, n5_d
+        jal   listProd
+        addu  $s2, $v0, $zero   # Move the result to s2
+        # ----- Try mult by 0
+        la    $a0, na_d
+        jal   listProd
+        addu  $s3, $v0, $zero   # Move the result to s3
+
+
+        addiu      $v0, $zero, 10    # system service 10 is exit
+        syscall                      # we are outta here.
+        ########################################################################
+        #  Write your code here. Leave main as is.
+        ########################################################################
+
+# Only works for unsigned numbers
+mulproc:
+	addiu $sp, $sp, -12
+	sw    $ra, 0x8($sp) 
+        sw    $a0, 0x4($sp)
+        sw    $a1, 0x0($sp)
+        addu  $v0, $zero, $zero   # result = 0
+        sltu  $t0, $a0, $a1
+        bne   $t0, $zero, loop_mult
+        # swap by xor
+        xor   $a0, $a0, $a1
+        xor   $a1, $a1, $a0
+        xor   $a0, $a0, $a1
+        # now a0 < a1
+loop_mult:
+        beq   $a0, $zero, leave_mult
+        addu  $v0, $v0, $a1
+        addiu $a0, $a0, -1
+        j     loop_mult
+leave_mult:
+        lw    $a1, 0x0($sp)
+        lw    $a0, 0x4($sp)
+        lw    $ra, 0x8($sp) 
+        addiu $sp, $sp, 12
+        jr    $ra # return
+
+
+listProd:
+        addiu $sp, $sp, -8
+        sw    $ra, 0x4($sp) 
+        sw    $a0, 0x0($sp) 
+        addiu $v0, $zero, 1
+        beq   $a0, $zero, leave_listProd
+        lw    $a0, 4($a0) # get next address
+        jal   listProd
+        addu  $a1, $v0, $zero  # move result into a1
+        lw    $a0, 0x0($sp)  # get my original parameter
+        lw    $a0, 0($a0)    # get data
+        jal   mulproc
+leave_listProd:
+        lw    $ra, 0x4($sp)
+        addiu $sp, $sp, 8
+        jr    $ra
+
+