Code Generation and Optimization

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Question 1

Match the description of several parts of a classic optimizing compiler in List - I, with the names of those parts in List - II:

• (1)

• (2)

• (3)

• (4)

Question 2

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 3

Consider the following expression

u*v+a-b*c

Which one of the following corresponds to a static single assignment from the above expressions

• x₁ = a - b y₁ = p * c x₂ = u * v y₂ = p + q

• x ₁ = a - b y₁ = x₂ * c x₃ = u * v y₂ = x₄ + y₃

• x₁ = a - b y₂ = x₁ * c x₂ = u * v y₃ = x₂ + y₂

• p = a - b q = p * c p = u * v q = p + q

Question 4

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 5

Peephole optimization is form of

• Loop optimization

• Local optimization

• Constant folding

• Data flow analysis

Question 6

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 7

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 8

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 9

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 10

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

• Local optimization

• Loop optimization

• Constant folding

• Strength reduction

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Compiler Design