Consider the following assembly program written for a $32-$bit MIPS machine with no delayed

branches.

li r$20,0$ # load immediate

li r$19,16000$

li r$15,0$

start:

ld r$1,0($r$20)$ # load into r$1$ from memory

add r$15,$ r$15,$ r$1$

addi r$20,$ r$20,32$ # add immediate

sub r$3,$ r$19,$ r$20$

bnez r$3,$ start # jump to start if r$3$ not equal with zero

a$)$ Identify the RAW, WAR and WAW conflicts in the assembly program.

b$)$ Assume that the program is run on a machine where there is a stall of $3$ cycles between

the writing and the reading of a register$[1]$

$.$ Rewrite the assembly program by inserting NOP

operations where there will be stalls. Unroll the loop in the program $4$ times in software

$($assembly$).$ Transform the program by register renaming such that the number of stalls is

minimized.