Code Generation and Optimization

Question 21

Consider the following source code :

c = a + b
d = c
c = c – e
a = d – e
b = b * e
b = d/b

Which of the following is correct optimization of given code?

• c = a + b
        t = b * e
        a = d – e
        b = d/t
        c = a

• c = a + b
        d = c
        c = c – e
        a = d – e
        b = d/b

• d = c
       c = c – e
       a = d – e
       b = b * e
       b = d/b

• None of the above

Question 22

Consider the code segment

int i, j, x, y, m, n;
 n=20;
 for (i = 0, i < n; i++)
  {
    for (j = 0; j < n; j++)
     {
        if (i % 2)
        {
         x + = ((4*j) + 5*i);
         y += (7 + 4*j);
        }
     }
  }
  m = x + y;

Which one of the following is false

• The code contains loop invariant computation

• There is scope of common sub-expression elimination in this code

• There is scope of strength reduction in this code

• There is scope of dead code elimination in this code

Question 23

Peephole optimization is form of

• Loop optimization
• Local optimization
• Constant folding
• Data flow analysis

Question 24

Which of the following is NOT represented in a subroutine\'s activation record frame for a stack-based programming language?

• Values of local variables
• Return address
• Heap area
• Information needed to access non local variables

Question 25

In compiler terminology reduction in strength means

• Replacing run time computation by compile time computation
• Removing loop invariant computation
• Removing common subexpressions
• replacing a costly operation by a relatively cheaper one

Question 26

Which of the following statements about peephole optimization is False?

• It is applied to a small part of the code
• It can be used to optimize intermediate code
• To get the best out of this, it has to be applied repeatedly
• It can be applied to the portion of the code that is not contiguous

Question 27

The use of multiple register windows with overlap causes a reduction in the number of memory accesses for I. Function locals and parameters II. Register saves and restores III. Instruction fetches

• I only
• II only
• III only
• I, II and III

Question 28

Substitution of values for names (whose values are constants) is done in

• Local optimization
• Loop optimization
• Constant folding
• Strength reduction

Question 29

Relative to the program translated by a compiler, the same program when interpreted runs

• Faster
• Slower
• At the same speed
• May be faster or slower

Question 30

In a resident – OS computer, which of the following systems must reside in the main memory under all situations?

• Assembler
• Linker
• Loader
• Compiler