4. Floating-Point Pipeline [20 marks]

Consider the following code fragment:

loop: l.d f0,0(r2)

l.d f2,0(r3)

div.d f0,f0,f2

s.d f0,0(r2)

sub.d f4,f4,f0

add.d f4,f4,f4

daddi r2,r2,#8

daddi r3,r3,#8

dsub r4,r5,r3

bnez r4,loop

'div.d' has 5 x-boxes. 'sub.d' and 'add.d' have 3 x-boxes. Functional

units are fully pipelined but not duplicated. The loop iterates 90 times.

Draw the space-time diagram of this code. Calculate the total execution

time of the loop.