Gate2017 cs Q24

0. Consider the following intermediate program in three address code
p = a - b
q = p * c
p = u * v
q = p + q
Which one of the following corresponds to a static single assignment form of the above code?

Answer
Comment
Array

Option : B
Explanation :
According to Static Single Assignment
--> A variable cannot be used more than once in the LHS
--> A variable should be initialized atmost once.
Now looking at the given options
1. a – code violates condition 1 as p₁ is initialized again in this statement: p₁ = u * v
2. c- code is not valid as q₁ = p₂ * c , q₂ = p₄ + q₃ – In these statements p₂, p₄, q₃ are not initialized anywhere
3. d- code is invalid as q₂ = p + q is incorrect without moving it to register
Therefore, option B is only correct option.

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