Trying to convert this c code into MIPS and run it in SPIM.
int A[100], B[100];
for(i=1; i<100; 1++){
A[i] = A[i-1] + B[i];
}
So far this is what I have.
# comments are delimted by has marks
.data
A: .word 0:100 # array of 12 integers
B: .word 0:100 # array of 12 integers
.text
main:
li $v0, 1 # load the value "1" into register $v0
li $t0, 1 # load the value "1" into register $t0
li $t1, 100 # load the value "100" into register $t1
blt $t0, $t1, loop # branches to Loop if $t0 < 100
la $t9, B
la $t8, A
loop:
sll $t0, $t0, 2
add $t2, $t9, $t0
lw $s4, 0($t9)
add $t3, $t0, -1
add $t4, $t8, $t3
lw $s5, 0($t4)
add $t5, $t2, $s5
add $t6, $s0, $t0
sw $t7, 0($t5)
addi $t0, $t0, 1
li $v0, 1 # system call for print_int
move $a0, $t0 # the sum to print
syscall # print the sum
When running in SPIM I get the following errors:
Exception occurred at PC=0x00400040 Bad address in data/stack read: 0x00000004 Exception occurred at PC=0x0040004c Unaligned address in inst/data fetch: 0x00000003 Exception occurred at PC=0x00400058 Bad address in data/stack read: 0x00000000 Attempt to execute non-instruction at 0x0040006c
Some direction would be nice. Thanks
Answer
You are branching to loop (blt $t0, $t1, loop) before you initialize the pointers to A and B. You need to move the blt $t0, $t1, loop to the end of your code, not have it at the beginning.
I hate to do this, but there are too many things wrong to list them all. Try this:
.data
A: .word 0:100 # array of 100 integers
B: .word 0:100 # array of 100 integers
.text
main:
li $t0, 4 # load the value "1" into register $t0
li $t1, 400 # load the value "100" into register $t1
la $t9, B
la $t8, A
loop:
add $t2, $t9, $t0 # $t2 = B + i
lw $s4, 0($t9) # $s4 = B[i]
add $t3, $t0, -4 # $t3 = i - 1
add $t4, $t8, $t3 # $t4 = A + i - 1
lw $s5, 0($t4) # $s5 = A[i - 1]
add $t5, $t8, $t0 # $t5 = A + i
add $t6, $s4, $s5 # $t6 = B[i] + A[i - 1]
sw $t6, 0($t5) # A[i] = $t6
addi $t0, $t0, 4 # i++
li $v0, 1 # system call for print_int
move $a0, $t6 # the sum to print
syscall # print the sum
blt $t0, $t1, loop # branches to Loop if $t0 < 100