What is three-address code and how is it tested in GATE Compiler Design?

Three-address code is an intermediate representation where each instruction has at most three operands (e.g., x = y op z). GATE tests generation of three-address code for expressions, assignment statements, conditionals, and loops, as well as recognizing valid intermediate representations like AST and Control Flow Graph.

What is the difference between synthesized and inherited attributes in GATE?

Synthesized attributes are computed from the attributes of child nodes in the parse tree, while inherited attributes are passed down from parent or sibling nodes. GATE tests S-attributed (only synthesized) and L-attributed definitions (synthesized plus left-to-right inherited), and which rules satisfy these definitions.

What code optimization techniques are important for GATE CS?

GATE tests common subexpression elimination, dead code elimination, constant folding, constant propagation, loop invariant code motion, strength reduction, and induction variable elimination. Data flow analysis (reaching definitions, live variable analysis) is used as the basis for these optimizations.

How should I prepare Compiler Design for GATE CS exam?

Focus on parsing (LL(1) table construction, LR item sets, conflict resolution), FIRST/FOLLOW set computation, syntax-directed translation (S-attributed and L-attributed), and three-address code generation. Practice all GATE previous year questions on ExamPrev with video solutions for the best preparation.

CS/IT Gate Subject

Aptitude and Reasoning
Engineering Mathematics
C Programming
Data Structure
Design Algorithm Analysis
Operating System
Computer Network
Digital Logic Design
Compiler Design
Database Management System
Theory of Computation

Compiler Design GATE previous year questions with answer

Ques 27 GATE 2015 SET-2

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 the control-flow-graph constructed for the above code, respectively, are

5 and 7

6 and 7

5 and 5

7 and 8

(b) is the correct answer.

Ques 28 Gate 2015 Set-1

Which one of the following is True at any valid state in shift-reduce parsing?

Viable prefixes appear only at the bottom of the stack and not inside

Viable prefixes appear only at the top of the stack and not inside

The stack contains only a set of viable prefixes

The stack never contains viable prefixes

(Parsing) is the correct answer.

Ques 29 GATE 2015 SET-1

A variable x is said to be live at a statement S_i in a program if the following three conditions hold simultaneously:
i. There exists a statement S_j that uses x
ii. There is a path from S_i to S_j in the flow graph corresponding to the program
iii. The path has no intervening assignment to x including at S_i and S_j

The variables which are live both at the statement in basic block 2 and at the statement in basic block 3 of the above control flow graph are

p, s, u

r, s, u

r, u

q, v

Ques 30 GATE 2015 SET-1

The least number of temporary variables required to create a three-address code in static single assignment form for the expression q + r / 3 + s - t * 5 + u * v / w is _______.

(8) is the correct answer.

Ques 31 GATE 2014 SET-3

The primary reason of using intermediate code in compilers is to

make parsing and semantic analysis simpler.

improve error recovery and error reporting.

increase the chances of reusing the machine-independent code optimizer in other compilers.

improve the register allocation.

Ques 32 GATE 2014 SET-3

Which of the following statements are CORRECT?
1) Static allocation of all data areas by a compiler makes it impossible to implement recursion.
2) Automatic garbage collection is essential to implement recursion.
3) Dynamic allocation of activation records is essential to implement recursion.
4) Both heap and stack are essential to implement recursion.

1 and 2 only

2 and 3 only

3 and 4 only

1 and 3 only

(d) is the correct answer.

Ques 33 GATE 2014 SET-3

Consider the basic block given below.
a = b + c
c = a + d
d = b + c
e = d – b
a = e + b
The minimum number of nodes and edges present in the DAG representation of the above basic block respectively are

6 and 6

8 and 10

9 and 12

4 and 4

(a) is the correct answer.

Ques 34 GATE 2014 SET-1

A canonical set of items is given below:
S → L. > R
Q → R.
On input symbol <, the set has

a shift-reduce conflict and a reduce-reduce conflict.

a shift-reduce conflict but not a reduce-reduce conflict.

a reduce-reduce conflict but not a shift-reduce conflict.

neither a shift-reduce nor a reduce-reduce conflict.

(d) is the correct answer.

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Compiler Design GATE previous year questions with answer

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