GATE CSE 2015 Set 2 | Question: 29

Question

Consider the intermediate code given below.

(1) i=1    
(2) j=1    
(3) t1 = 5 * i    
(4) t2 = t1 + j    
(5) t3 = 4 * t2    
(6) t4 = t3    
(7) a[t4] = -1    
(8) j = j + 1    
(9) if j <= 5 goto (3)    
(10) i = i +1    
(11) if i < 5 goto (2)

The number of nodes and edges in control-flow-graph constructed for the above code, respectively, are

• A. $5$ and $7$
• B. $6$ and $7$
• C. $5$ and $5$
• D. $7$ and $8$

Comments

1. 5 should be along with 34 in same block.

2. Logically, line-7 is wrong. How is i = i -1 and goto 3 in same line. It doesn't make sense. And even if we try to make some sense out of it, we can get 6 nodes and 6 edges, considering respective basic blocks: [Start, 12, 345, 6, 7, End] and edges without including an edge from 7->end.

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Answe is 6,7

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@princeit07 blocks 10 and 11 can be in the same block, right?

Answer 1

answer is b

Comments

How B explain Your Words

Answer 2

here is correct control follow the diagram

 

Answer 3

1. First statement is a leader. 2.target of go to is leader. 3.next statement of goto is leader. so

1.leader.

2.leader.

3.leader

10.leader.

now there will be 4 basic blocks made out of it.

Add start and stop to these four blocks.

Also number for nodes would be 6.and edges would be 7..

 

1 is b1.

2 is b2.

3-9 is b3

10-11 is b4