Question

[5] Consider the following MIPS loop:

LOOP: slt \(t2, \)0, \(t1

beq \)t2, \(0, DONE

subi \)t1, \(t1, 1

addi \)s2, \(s2, 2

j LOOP

DONE:

2.26.1 [5] <§2.7> Assume that the register \)t1 is initialized to the value 10. What is the value in register \(s2 assuming \)s2 is initially zero?

2.26.2 [5] <§2.7> For each of the loops above, write the equivalent C code routine. Assume that the registers \(s1, \)s2, \(t1, and \)t2 are integers A, B, i, and temp, respectively.

2.26.3 [5] <§2.7> For the loops written in MIPS assembly above, assume that the register $t1 is initialized to the value N. How many MIPS instructions are executed?

Short answer

2.26.1

The value in register $s2 is twenty(20) by assuming $s2 is initially zero.

2.26.2

The equivalent C code of the given MIPS assembly language program:

While (i>0)

i=i-1;

B=B+2;

2.26.3

The specified MIPS instructions are executed for (5N+2) times.

Step-by-step solution

Define the concept.

2.26.1

In the given code, the purpose of using the MIPS instruction “slt $t2, $0, $t1”is if $t1 is greater than 0 then $t2=1 else $t2=0.The “beq $t2, $0, DONE”is used for going to the statement “DONE” if the value of “$t2” is equal to the “$0”.The MIPS instruction“subi $t1, $t1, 1” is used for subtracting 1 from “$t1” and store in “$t1”. The purpose of using the MIPS instruction“addi $s2, $s2, 2” is to add “2” with the “$s2” and store it in the “$s2”. The“j LOOP”is usedfor transferring the sequence of the program to the“LOOP”.

2.26.2

The while loop is used for implementing the equivalent C code of the given MIPS assembly language program.

The format of while loop in c:

While(condition)// “while” is the keyword.

{

Statement(s);// while the condition is true till this statement will be executed.

}

2.26.3

LOOP:slt $t2, $0, $t1//If $t1 is greater than $t0 then $t2=1 else $t2=0

beq $t2, $0, DONE//if $t2 is equal to $0 then go to the statement “DONE”

subi $t1, $t1, 1//$t1=$t1-1

addi $s2, $s2, 2//$s2=$s2+1

j LOOP// go to LOOP

DONE:

The $t1 is initialized to the value N [By assuming].

Then, the MIPS instructions are executed for times.

Determine the calculation.

2.26.1

In the given code,

LOOP:slt $t2, $0, $t1//If $t1 is greater than $t0 then $t2=1 else $t2=0

beq $t2, $0, DONE//if $t2 is equal to $0 then go to the statement “DONE”

subi $t1, $t1, 1//$t1=$t1-1

addi $s2, $s2, 2//$s2=$s2+2

j LOOP// go to LOOP

DONE:

$t1 at the top = 10 and $t1 at the top = 9

…

…

…

… [After 10 times of executions]

$t1 at the top = 1 and $t1 at the top = 0

For 10 times of executions, $s2 = 2*10 = 20.

The value in register $s2 is twenty (20) by assuming $s2 is initially zero.

2.26.2

The equivalent C code of the given MIPS assembly language program:

While(i>0)// while I is greater than zero

2.26.3

The $t1 is initialized to the value N[By assuming,].

When the value of “i” is zero (0) then the first two instructions are executed and after that, it will go to the statement “DONE”.

Hence, the number of execution = .