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A copy instruction of the form x = y in intermediate code

  • A.is required by the language standard after every assignment
  • B.indicates that the two names refer to different types
  • C.is often removable by a later copy propagation pass
  • D.cannot be removed without changing the program's meaning

Answer: C

Correct answer: is often removable by a later copy propagation pass

Copy propagation replaces later uses of x with y, after which the copy itself may be dead and removable. Copies arise in quantity from the translation of assignments and from parameter passing, so this is one of the more productive of the simple optimisations.

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