GATE CS 2014 Set 1 — Question 27

MCQ+1 / -0.33EasyCode OptimizationCompiler Design

Compiler Design → Code Optimization

Last updated 5 September 2026

Question

Which one of the following is FALSE ?

Correct answer (D) x = 4 5 \Rightarrow x = 20 is an example of common subexpression elimination. Solution Option (D) describes constant folding (evaluating constant expressions at compile time), not common subexpression elimination. Common subexpression elimination involves identifying and reusing results of expressions that are computed more than once. (A) is the definition of a basic block. (B) Available expression analysis is indeed used to identify common subexpressions. (C) Live variable analysis is used to identify variables that are defined but never used, allowing for dead code elimination. Turn this into a strength. Explore AI-powered practice and doubt support with Success Tracker.

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Correct answer (D) x = 4 5 \Rightarrow x = 20 is an example of common subexpression elimination. Solution Option (D) describes constant folding (evaluating constant expressions at compile time), not common subexpression elimination. Common subexpression elimination involves identifying and reusing results of expressions that are computed more than once. (A) is the definition of a basic block. (B) Available expression analysis is indeed used to identify common subexpressions. (C) Live variable analysis is used to identify variables that are defined but never used, allowing for dead code elimination.

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