CS0445 Project 1
             Due February 9 (at the beginning of class).

The purpose of  this  assignment  is  to  write  your  first  assembly
language program and to test your ability to analyze program execution
time.  See the announcements web page for details about what to submit.

PROJECT:

Write a program in MIPS R2000/R3000 Assembly  language  that  computes
and  outputs  the  CPU  execution  time for a program in nano-seconds.
Assuming that instructions requires 3, 4 or 5 cycles to  execute,  the
user should be prompted for the number of each type of instructions in
the program as well as the clock period (in nano-seconds).

     EXAMPLE:

     Enter the number of 3-cycle instructions: 25
     Enter the number of 4-cycle instructions: 30
     Enter the number of 5-cycle instructions: 12
     Enter the clock period in nano-seconds: 10

     CPU time =  2550 ns

Use your program to compare the efficiency of the two  programs  prog1
and    prog2    found   in   files   ~melhem/spim/examples/prog1   and
 ~melhem/spim/examples/prog2 on the cis unix system. Do not include the
last  two  lines  of  the  programs (li and syscall) in your analysis.
Assume that the clock period is 8 nano-seconds and that

    - "la", "li" and "move" are 3-cycle instructions,
    - "add", "addi", "slt" and "bne" are 4-cycle instructions,
    - "sw" is a 5-cycle instructions.

You will have to trace prog1 and prog2 by hand to determine the number of
instructions of each type that actually execute.

It may be clearer for you to start by writing a C++ program that computes
the execution times, and then convert your C++ program to assembly language.

=======================================================================

# ~melhem/spim/examples/prog1 contains the following program
#   Declare data 
    .data
     array:  .word 1,2,3,4,5,6,7,8
#   A program to zero the above array 
    .text
    .globl main
     main:  la   $s0, array     # put base address of array in $s0 
            li   $s1, 8         # put array size in $s1

	    move $t0, $zero     # i = 0
      loop: add  $t1,$t0,$t0    # $t1 = i * 2
            add  $t1,$t1,$t1    # $t1 = i * 4
	    add  $t2,$s0,$t1    # $t2 = &array[i]
	    sw   $zero,0($t2)   # array[i] = 0
            addi $t0,$t0,1      # i = i + 1
	    slt  $t3,$t0,$s1    # $t3 = (i < array size)
	    bne  $t3,$zero,loop # if () go to loop
             

            li  $2, 10       # prepare to exit with syscall 10
            syscall          # make call

# end of program

===================================================================

# ~melhem/spim/examples/prog2 contains the following program
#   Declare data 
    .data
     array:  .word 1,2,3,4,5,6,7,8

#   A program to zero the above array using pointers.
    .text
    .globl main
     main:  la   $s0, array     # put base address of array in $s0 
            li   $s1, 8         # put array size in $s1

	    move $t0, $s0       # p = &array[0]
            add  $t1,$s1,$s1    # $t1 = size * 2
            add  $t1,$t1,$t1    # $t1 = size * 4
	    add  $t2,$s0,$t1    # $t2 = &array[size]
      loop: sw   $zero,0($t0)   # memory[p] = 0
            addi $t0,$t0,4      # p = p + 4
	    slt  $t3,$t0,$t2    # $t3 = (p < &array[size])
	    bne  $t3,$zero,loop # if () go to loop


            li  $2, 10       # prepare to exit with syscall 10
            syscall          # make call

# end of program