List of top Compiler Design Questions

For a statement \(S\) in a program, in the context of liveness analysis, the following sets are defined: 
\(USE(S)\) :  the set of variables used in \(S\) 
\(IN(S)\) :  the set of variables that are live at the entry of \(S\) 
\(OUT(S)\) :  the set of variables that are live at the exit of \(S\) 

Consider a basic block that consists of two statements, \(S_1\) followed by \(S_2\). Which one of the following statements is correct?

Consider the following ANSI C code segment: 

z = x + 3 + y->f1 + y->f2; 
for (i = 0; i < 200; i = i + 2){ 
	if (z > i) { 
		p = p + x + 3; 
		q = q + y->f1; 
	} else { 
		p = p + y->f2; 
		q = q + x + 3; 
	} 
}  

Assume that the variable \(y\) points to a struct (allocated on the heap) containing two fields \(f1\) and \(f2\), and the local variables \(x, y, z, p, q,\) and \(i\) are allotted registers. Common sub-expression elimination (CSE) optimization is applied on the code. The number of addition and dereference operations (of the form \(y \rightarrow f1\) or \(y \rightarrow f2\)) in the optimized code, respectively, are: 
 

Consider the following ANSI C program: 

int main() { 
    Integer x; 
    return 0; 
}

Which one of the following phases in a seven-phase C compiler will throw an error?