Assignment 2: MIPS Instructions and Assembly Language

CDA 4205 Computer Architecture 
Assignment 2: MIPS Instructions and Assembly Language
1.     (4 pts) Bits have no inherent meaning. Given the 32-bit pattern:
1010 1101 0001 0000 0000 0000 0000 0010
What does it represent, assuming it is …
a)    A 2's complement signed integer?
b)    A MIPS instruction?

2.    (4 pts) Determine the absolute value of a signed integer. Show the implementation of the following pseudo-instruction using three real instructions:
abs $t1, $t2 

3.    (16 pts) For each pseudo-instruction in the following table, produce a minimal sequence of actual MIPS instructions to accomplish the same thing. You may use the $at for some of the sequences. In the following table, imm32 refers to a 32-bit constant.
a)    move $t1, $t2
b)    clear $t5
c)    li $t5, imm32
d)    addi $t5, $t3, imm32
e)    beq $t5, imm32, Label
f)    ble $t5, $t3, Label
g)    bgt $t5, $t3, Label
h)    bge $t5, $t3, Label

4.    (8 pts) Translate the following statements into MIPS assembly language. Assume that a, b, c, and d are allocated in $s0, $s1, $s2, and $s3. All values are signed 32-bit integers.
a)    if ((a > b) || (b > c)) {d = 1;}
b)    if ((a <= b) && (b > c)) {d = 1;}

5.    (8 pts) Consider the following fragment of C code:
for (i=0; i<=100; i=i+1) { a[i] = b[i] + c; }
Assume that a and b are arrays of words and the base address of a is in $a0 and the base address of b is in $a1. Register $t0 is associated with variable i and register $s0 with c. Write the code in MIPS.

6.    (8 pts) Add comments to the following MIPS code and describe in one sentence what it computes. Assume that $a0 is used for the input and initially contains n, a positive integer. Assume that $v0 is used for the output.


begin:     addi $t0, $zero, 0
addi $t1, $zero, 1
loop:     slt $t2, $a0, $t1
bne $t2, $zero, finish
add $t0, $t0, $t1
addi $t1, $t1, 2
j loop
finish: add $v0, $t0, $zero

7.    (12 pts) The following code fragment processes an array and produces two important values in registers $v0 and $v1. Assume that the array consists of 5000 words indexed 0 through 4999, and its base address is stored in $a0 and its size (5000) in $a1. Describe what this code does. Specifically, what will be returned in $v0 and $v1?
add $a1, $a1, $a1
add $a1, $a1, $a1
add $v0, $zero, $zero
add $t0, $zero, $zero
outer:         add $t4, $a0, $t0
lw $t4, 0($t4)
add $t5, $zero, $zero
add $t1, $zero, $zero
inner:         add $t3, $a0, $t1
lw $t3, 0($t3)
bne $t3, $t4, skip
addi $t5, $t5, 1
skip:         addi $t1, $t1, 4
bne $t1, $a1, inner
slt $t2, $t5, $v0
bne $t2, $zero, next
add $v0, $t5, $zero
add $v1, $t4, $zero
next:         addi $t0, $t0, 4
bne $t0, $a1, outer
    Submission Requirements
    Your solutions must be in a single file with a file name yourname-hw1.
    If scanned from hand-written copies, then the writing must be legible, or loss of credits may occur.
    Only submissions via the link on Canvas where this description is downloaded are graded. Submissions to any other locations on Canvas will be ignored.
    Late submissions are accepted for a maximum of 3 late days with 20% assignment credit off as late penalization. Assignments submitted after 3 late days will not be accepted.