cs270 sp22 hw05 code

# File: hw05-assem.s
# Done by: Carmen Bland Jr.

.text                		      
.globl main                   

main:
                addi sp, sp -8          #add space for 2 words
                sw ra, 0(sp)            #push return address to stack
                sw x10, 4(sp)           #push x10 (param for fibonacci/input in main)
                addi x10, zero, 10      #input = 10
                jal ra, fibonacci       #call fibonacci
                add x18, zero, x10	#result = fib(input)
                lw ra 0(sp)             #load return address
                addi sp, sp, 8          #pop stack
                addi x10, zero, 0	#return 0
                jalr zero, ra, 0        #exit program

        fibonacci:
                addi sp, sp -4          #add space for 1 word
                sw ra, 0(sp)            #push return address to stack
                addi x5, zero, 2        #set up x5 as the comparison register
                addi x6, zero, 0        #set up x6 as zero (for reset)
                bge x10, x5, else       #if !(n < 2), goto else
                beq zero, zero, exit    #skip else
                
        else:
                addi sp, sp, -12        #add space for 3 words
                addi x10, x10, -1       #compute n-1
                sw x10, 0(sp)           #push x10 (n-1) to stack
                sw x7, 4(sp)		#push x7 to stack
                sw x8, 8(sp)            #push x8 to stack
                jal ra, fibonacci	#call fib
                add x7, zero, x10	#copy result from fib(n-1)
                lw x10, 0(sp)		#restore x10
                addi x10, x10, -1       #compute n-2
                jal ra, fibonacci       #call fibonacci (recursive call)
                add x8, zero, x10	#copy result from fib(n-2)
                add x10, x7, x8		#put n = (n-1) + (n-2)
                lw x7, 4(sp)            #restore x7
                lw x8, 8(sp)            #restore x8
                addi sp, sp, 12         #pop stack

        exit:
                lw ra, 0(sp)            #load return address
                addi sp, sp, 4          #pop stack
                jalr zero, ra, 0        #exit function