DAG ace test question

Question

How does answer change when it is in SSA  form? does answer remains 4 or 5

Answer 1

Here last statement will not be executed. The main motive of DAG is elimination of common sub-expression.So, By only first two statements, I think your answer is also 4 nodes.

Comments

The main motive of DAG is elimination of common sub-expression. how?

does answer changes in SSA

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In DAG, we never compute the already computed part. That is if a sub-expression is common, we don't have to compute it every time it occurs. We have to compute it only once and reuse it. Here c+d is already computed, so we will not compute it again.

I am sorry but I cannot say about SSA.

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$d=c+d$ is unreachable code.