Code Optimization Questions

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11.

The identification of common sub-expression and replacement of run time computations by compile-time computations is------

A

Local optimization

B

Constant folding

C

Loop optimization

D

Data flow analysis

Correct Answer: B

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12.

Which of the following class of statement usually produces no executable code when compiled?

A

Declaration

B

Assignment statements

C

Input and output statements

D

Structural statements

Correct Answer: A

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13.

Code optimization is responsibility of--------

A

Application programmer    

B

System programmer

C

Operating system 

D

All of the above.

Correct Answer: B

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14.

Dead-code elimination in machine code optimization refersto -----------

A

Removal of all labels.

B

Removal of values that never get used.

C

Removal of function which are not involved.

D

Removal of a module after its use.

Correct Answer: B

Removal of values that never get used.

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15.

Which of the following statement is false?

A

Flow graph is used to represent DAG.

B

Three address code is the input to the code generator.

C

The first statement of three address code is always leader of the first basic block.

D

Transformation of block is needed for code optimization.

Correct Answer: A

Flow graph is used to represent DAG.

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16.

-------- is the final phase of compiler.

A

Semantic analysis     

B

Code generation

C

Target code generation

D

Syntax analysis

Correct Answer: B

Code generation

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17.

Consider the following intermediate program in three address codep = a - b
q = p * c
p = u * v
q = p + q
Which one of the following corresponds to a static single assignment form of the above code?

A

p1 = a - b
q1 = p1 * c
p1 = u * c
q1 = p1 + q1

B

p3 = a - b
q4 = p3 * c
p4 = u * c
q5 = p4 + q4

C

p1 = a - b
q1 = p2 * c
p3 = u * c
q2 = p4 + q3

D

p1 = a - b
q1 = p * c
p2 = u * c
q2 = p + q

Correct Answer: B

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18.

Some code optimizations are carried out on the intermediate code because------

A

They enhance the portability of the compiler to other target processors

B

Program analysis is more accurate on intermediate code than on machine code

C

The information from dataflow analysis cannot otherwise be used for optimization

D

The information from the front end cannot otherwise be used for optimization

Correct Answer: A

They enhance the portability of the compiler to other target processors

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19.

Peephole optimization is form of------

A

Loop optimization   

B

Local optimization

C

Constant folding 

D

Data flow analysis

Correct Answer: B

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20.

In compiler terminology reduction in strength means-----

A

Replacing run time computation by compile time computation

B

Removing loop invariant computation

C

Removing common subexpressions

D

replacing a costly operation by a relatively cheaper one

Correct Answer: D

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