GATE2003-59

Question

Consider the syntax directed definition shown below.

$S \rightarrow \mathbf{ id :=} E$	$\{gen(\mathbf{ id}.place = E.place;);\}$
$E \rightarrow E_1 + E_2$	$\{t = newtemp();$
	$gen(t = E_1.place + E_2.place;);$
	$E.place = t;\}$
$E \rightarrow id$	$\{E.place = \mathbf{id}.place;\}$

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 t_i'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

• A. $X = Y + Z$
• B. $t_1 = Y+Z; X=t_1$
• C. $t_1 =Y; t_2=t_1 +Z; X=t_2$
• D. $t_1 =Y; t_2=Z; t_3=t_1+t_2; X=t_3$

Answer 1

B)

using given semantic rules.

Answer 2

x=y+z

three address code

 

operand op1 op2  result   

+           y      z      t1

=          t1              x

t1=y+z

x=t1

so ans is b

Answer 3

answer - B