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I'm practicing data and control dependencies, but having trouble detecting them. For this example, I'm assuming this pipeline is fully bypassed (with forwarding). I think the only data dependency is i3 on i2. Is this correct? I also don't know how to detect the control dependency. I know there will be one because of the bne, but not sure how and on which one...

i1: lw $t0, 10($t1)
i2: lw $t4, 3($t2)
i3: addiu $t0, $t4, 3
i4: addu $t0, $t0, $t2
i5: addiu $t2, $t2, -8
i6: addiu $t1, $t1, -4
i7: bne $t1, $0, i1
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1 Answer 1

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There are no control dependencies in the code fragment. The non-transitive true (read-after-write) dependencies are:

  • $i_2\ \delta^f\ i_3$ via register $t_4$
  • $i_3\ \delta^f\ i_4$ via register $t_0$
  • $i_6\ \delta^f\ i_7$ via register $t_1$

There are also output (write-after-write) dependencies:

  • $i_1\ \delta^o\ i_3$ via register $t_0$
  • $i_3\ \delta^o\ i_4$ via register $t_0$
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