Given the following sequence of instructions to be executed on a 5-stage pipelin

Question

Given the following sequence of instructions to be executed on a 5-stage pipelined datapath as decrypted in our textbook: I1: add $8, $12,$10 12: SW $9,0 ($8) 13: lw $8,4($9) I4: and $12,$12,$8 15: SW $8,0($9) a. List true dependencies in the given sequence in the format of (register involved producer instruction, consumer instruction). Use labels to indicate instructions For example: ($0, I10, I11) means a true dependence between instruction I10 and I11: value of register $0 is generated by I10 and used by I11. Do NOT list output or anti-dependences. b. If there is no forwarding or hazard detection, no reordering allowed, insert nops to ensure correct execution. c. Repeat b. but allow instruction reordering nops should be inserted only when a hazard cannot be avoided by reordering instructions d. If there is full forwarding support, draw multiple-cycled pipeline diagram to show the execution of the original sequence (NOT the reordered version). Use arrows to mark forwardings clearly in your diagram. Each arrow should point from instruction/stage that generates the data rightarrow instruction/stage that consumes the data. Also mark the necessary pipeline stalls.

Explanation / Answer

a)Dependencies list:-

I1: $12,$10
I2: [$8]
I3: [$9]+(4*4)
I4: $12,$8
I5: [$9]

b)
I1: add $8,$12,$10
nop
I2:sw $9,0($8)
nop
nop
nop
lw $8,4($9)
nop
and $12,$12,$8
nop
sw $8,0($9)

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