Exercise 8.

We consider the following basic block

a := b + c
z := a * a
x := 0
y := b + c
w := y * y
u := x + 3
v := u + v

Assume that only v and z are live at the exit of this block. Applying the following optimizations

• common sub-expressions elimination
• copy propagation
• dead code elimination

explain how the above basic block can be transformed into another one which has only 3 TAC statements. Note that each optimization can be applied several times.

Answer 8