Match the optimization technique in List-I with its appropriate classification…
Match the optimization technique in List-I with its appropriate classification in List-II.
Answer: A. P-3, Q-2, R-1, S-4 — Correct matching: P-3, Q-2, R-1, S-4 P) Constant folding: Evaluating expressions with only constants at compile time (for example, replacing x = 2 * 100 with…
- A.
P-3, Q-2, R-1, S-4
- B.
P-1, Q-2, R-4, S-3
- C.
P-3, Q-4, R-1, S-2
- D.
P-4, Q-1, R-3, S-2
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Show answer & explanation
Correct answer: A
Correct matching: P-3, Q-2, R-1, S-4
P) Constant folding: Evaluating expressions with only constants at compile time (for example, replacing x = 2 * 100 with x = 200). This is performed within basic blocks and does not depend on target-machine details, so it is a machine-independent, local optimization.
Q) Strength reduction: Replacing expensive operations inside loops with cheaper ones (for example, converting multiplication in a loop into repeated addition). It targets loop bodies and is independent of the machine, so it is a machine-independent, loop optimization.
R) Register allocation: Deciding which variables are kept in CPU registers depends on the target architecture (number and types of registers, calling conventions, etc.). Because it relies on machine-specific details, it is a machine-dependent optimization.
S) Dead code elimination: Removing instructions or code paths whose results are never used or are unreachable. This typically requires data-flow analysis across basic blocks or entire functions, so it is a machine-independent, global optimization.
Therefore the correct mapping is: P → machine-independent, local; Q → machine-independent, loop; R → machine-dependent; S → machine-independent, global.