Loop-carried dependences...cont'd

What is a loop-carried dependence?

• Consider two iterations and
• A dependence occurs between two statements and (not necessarily distinct), when an assignment in refers to the same location as a use in
• In the example,

  

  • The assignment is ``A[ ] := ...''
  • The use is ``... := A[ -1] ...''
  • These refer to the same location when
  • Thus , ie the assignment is in an earlier iteration
• Notation: