Hi everyone
First post here on this forum. I'm awfully stuck in an exercice I have to complete as an assignment. I'm studying computer science and this has been my first year.
This is what I am supposed to do:
Your project consists of implementing the following C code:
int f1(int a) {
if (a < 3)
return (a);
else
return (f2(a-1, a-2) + f2(a-2, a-1));
}
int f2(int x, int y) {
return 2*f1(x) + y;
}This is what I have so far:
.text
main:
# retrieve input from user
li $v0, 5 # load code for read int
syscall # syscall for read int
# store user input as first operand
move $a0, $v0 # store read int as argument
# calculate result
jal f1 # function call
j display
j exit
f1:
# make room on stack for $ra and $a0
move $fp, $sp # new fp is sp
addi $sp, $sp, -8 # sp gets bigger
# store both those registers on the stack
sw $a0, 0($fp) # store function argument
sw $ra, -4($fp) # store return address
# recursive condition
slti $t0, $a0, 3 # if a < 3, t0 = 1
li $t1, 1 # Load int into t1 for comparison
bne $t0, $t1, f1_L1 # Branch if a >= 3
move $v0, $a0 # set a0 as result
j f1_return # go to return code
# recursive calls
f1_L1:
addi $a1, $a0, -1 # Prepare first argument
addi $a2, $a0, -2 # Prepare second argument
jal f2_L1 # Function call
add $v0, $v0, $v1
addi $a1, $a0, -2
addi $a2, $a0, -1
jal f2_L1
add $v0, $v0, $v1
# return sequence f1
f1_return:
# restore $ra and $a0 registers
lw $ra, -4($fp) # restore previous return address
lw $a0, 0($fp) # restore previous function argument
move $sp, $fp # sp gets smaller (remove frame)
jr $ra # continue at return address
# f2
f2_L1:
# make room on stack for $ra, $a1, $a2
move $fp, $sp # new fp is sp
addi $sp, $sp, -12 # sp gets bigger
# store all three registers on the stack
sw $a2, 0($fp) # store function argument 2
sw $a1, -4($fp) # store function argument 1
sw $ra, -8($sp) # store return adress
move $a0, $a1
jal f1
li $t0, 2
mult $v0, $t0
mflo $v1
add $v1, $v1, $a2
# return sequence f2
f2_return:
# restore $ra, $a1, $a2
lw $ra, -8($fp) # restore previous return address
lw $a1, -4($fp) # restore previous function argument
lw $a2, 0($fp)
move $sp, $fp # sp gets smaller (remove frame)
jr $ra # continue at return address
# display result
display:
move $a0, $v0 # store arg for syscall
li $v0, 1 # load code for display int
syscall # syscall for display int
# exit program
exit:
li $v0, 10 # load code for exit
syscall # syscall for exitWhen I run this code, I get an error:
Error in cs06.asm line 42: Runtime exception at 0x00400058: arithmetic overflow
I have highlighted this line in the code.
Anyone sees anything to help me ? Thanks.