Def-Use

• Def (definition) is a place in a program where variable gets a value.
  • Explicit assignment x = 42
  • Implicit assignment, like function parameter or loop variable
  • Initialization (declaration plus initial value)
  • Change operation, e.g x++
• Def-Use chain is a a list connecting a def to all its uses
• Dead Code Elimination
  • A variable is live if its current value may be read in the future before it's redefined.