Which ONE of the following techniques used in compiler code optimization uses…

Correct answer: Register assignment to variables (register allocation).

Why: Live variable analysis is a backward data-flow analysis that computes, at each program point, which variables may be used in the future (the live-in and live-out sets). It identifies the live ranges of variables, and that information is essential for register allocation.

• Builds the interference graph: two variables that are live at the same time interfere and cannot share a register.

• Guides spilling decisions: variables with large live ranges or high interference are candidates to be moved to memory.

• Helps register coalescing and other allocation heuristics by revealing when variables do not overlap in time.

Notes on the other choices:

• Run-time function call management deals with calling conventions, stack frames, and parameter passing; it is not driven by live variable analysis.

• Strength reduction is a local arithmetic optimization (e.g., replacing multiplication with addition) and does not require liveness information.

• Constant folding evaluates constant expressions at compile time and does not depend on live variable analysis.