Data dependencies

• Instruction (statement) j dependent on i if

  • Transitivity: Instruction j dependent on k and k dependent on i

• Dependence is a program property

• Hazards (RAW in this case) and their (partial) removals is a pipeline organization property

• Code scheduling goal

  • Maintain dependence and avoid hazard (pipeline is exposed to the compiler)
  • Eliminate dependence by modifying code

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