Ace Test Series: Compiler Design - Intermediate Code

Question

Consider the following expression:

(a+a*(b-c)+(b-c)*d)

What is the minimum number of three address statements for the expression?

My question is whether we should optimize the expression before evaluating it or go as it is. For instance the above expression can be optimized as (a+(b-c)*(a+d)) which would generate lesser number of statements.

Answer 1

5 statements would be needed.

t1=b-c;

t2=a*t1;

t3=d*t1;

t4=t2+t3;

t5=a+t4;

Never try to optimise the expression unless they say algebraic simplifications or code optimisations are allowed or place a restriction on number of temorary variables.

Comments

Converting the code to ICG makes code optimization much simpler. Hence all the optimization should be done only after converting it to ICG. Hence no optimization should be done in IGC itself.