GATE CS : Compiler Design Champion Quiz 3 for GATE & PSU CS Exams

Question 1

In a bottom-up evaluation of a syntax directed definition, inherited attributes can

Question 2

Which of the following suffices to convert an arbitrary CFG to an LL(1) grammar?

Question 3

Consider the grammar rule E → E₁ - E₂ for arithmetic expressions. The code generated is targeted to a CPU having a single user register. The subtraction operation requires the first operand to be in the register. If E₁ and E₂ do not have any-common sub-expression, in order to get the shortest possible code

Question 4

Let G be a grammar is used for arithmetic expressions. The grammar G is shown below with sematic actions and attribute “sign” can contain either 0 or 1.
E

E₁+E₂ [E.sign=E₂.sign]
E

E₁

(E₂) {E.sign=E₁.sign

E₂.sign}
E

E₁/E₂ {if (E₁.sign==0) then E.sign=1 else E.sign=0}
E

+E₁ {E.sign=0}
E

-E₁ {E.sign=1}
E

id {E.sign=0}
Find the attribute alue at the root E for the given input -id

(-id+id)
[Note: E

E₁+E₂ is same as E

E+E].

Question 5

Find the C statement which has a syntax error.

Question 6

Consider the grammar with the following translation rules and E as the start symbol.
E→E₁#T {E.value=E₁.value*T.value}
T {E.value=T.value}
T→T₁&F {T.value=T1.value+F.value}
F {T.value=F.value}
F→num {F.value=num.value}
Compute E.value for the root of the parse tree for the expression: 2#3&5#6&4.

Question 7

Consider the following translation scheme.
S →ER
R →*E {print (‘*’);}R|ε
E →F + E {print (‘+’);}|F
F →(S)|id {print (id.value);}
Here id is a token that represents an integer and id.value represents the corresponding integer value. For an input '2 * 3 +4', this translation scheme prints

Question 8

Type checking is normally done during ___

Question 9

Consider the syntax directed translation scheme (SDTS) given in the following. Assume attribute evaluation with bottom-up parsing, i.e., attributes are evaluated immediate ly after a reduction.

E $\to$ E $_{1}$ * T {E.val = E $_{1}$ .val * T.val}

E $\to$ T {E.val = T.val}

T $\to$ F - T $_{1}$ {T.val = F.val - T $_{1}$ .val}

T $\to$ F {T.val = F.val}

F $\to$ 2 {F.val = 2}

F $\to$ 4 {F.val = 4}

Using this SDTS, for the expression 4 – 2 – 4 * 2 compute its E.val.

Question 10

Consider the syntax directed definition shown below
S → id : = E {gen(id.place = E.place;);}
E → E₁ + E₂ {t = newtemp( );
gen(t = E₁.place + E₂.place;);
E.place = t;}
E →id {E.place = id.place;}
Here, gen is a function that generates the output code, and newtemp is a function that returns the name of a new temporary variable on every call. Assume that ti’s are the temporary variable names generated by newtemp. For the statement ‘X : = Y + Z’, the 3-address code sequence generated by this definition is