Consider the following loop.

LOOP: LDUR X$10,[$X$1,$ #$0]$

LDUR $x_{11},[x1,$#$8]$

ADD $12,x10,x11$

STUR $x12,[x1,$#$-8]$

SUBI X$1,$ X$1,$ #$16$

CBNZ X$12,$ LOOP

$($a$)$ Assume that data and control hazards are handled by simply stalling the pipeline $($i$.$e$.$ inserting NOP instructions where necessary$).$ Show the pipeline timing diagram of the code execution.

$\backslash$table$[[$Cycle number:,$1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20],[$LOOP: LDUR X$10,[$X$1,$ #$0],$IF$,$ID$,$EX$,$ME$,$WB$,,,,,,,,,,,,,,,],[$LDUR X$11,[$X$1,$ #$8],,$IF$,,,,,,,,,,,,,,,,,,],[$ADD X$12,$ X$10,$ X$11,,,,,,,,,,,,,,,,,,,,],[$STUR X$12,x1,$#$-8,,,,,,,,,,,,,,,,,,,,],[$SUBI X$1,$ X$1,$ #$16,,,,,,,,,,,,,,,,,,,,],[$CBNZ X$12,$ LOOP,,,,,,,,,,,,,,,,,,,,$],[,,,,,,,,,,,,,,,,,,,,],[2^{nd}$ iteration: LDUR X$10,[$X$1,$ #$0],,,,,,,,,,,,,,,,,,,,]]$

$($b$)$ Can you reorder the code to reduce the number of stalls? If yes, show the reordered code.

$($c$)$ Show the pipeline timing diagram of the code execution with data forwarding and assume that the branch is handled by predicting it as taken and the branch target address is calculated at the ID stage.

$\backslash$table$[[$Cycle number:,$1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20],[$LOOP: LDUR X$10,[$X$1,$ #$0],$IF$,$ID$,$EX$,$ME WW$,,,,,,,,,,,,,,,,],[$LDUR X$11,[$X$1,$ #$8],,$IF$,,,,,,,,,,,,,,,,,,],[$ADD X$12,$ X$10,$ X$11,,,,,,,,,,,,,,,,,,,,],[$STUR X$12,[$X$1,$ #$-8],,,,,,,,,,,,,,,,,,,,],[$SUBI X$1,$ X$1,$ #$16,,,,,,,,,,,,,,,,,,,,],[$CBNZ X$12,$ LOOP,,,,,,,,,,,,,,,,,,,,$],[,,,,,,,,,,,,,,,,,,,,],[2^{nd}$ iteration: LDUR X$10,[$X$1,$ #$0],,,,,,,,,,,,,,,,,,,,]]$

$($d$)$ What is the speedup for the execution of $($c$)$ over $($a$)?$