Use-define Chain - Method of Building A use-def (or ud) Chain

Method of Building A use-def (or ud) Chain

  1. Set definitions in statement s(0)
  2. For each i in, find live definitions that have use in statement s(i)
  3. Make a link among definitions and uses
  4. Set the statement s(i), as definition statement
  5. Kill previous definitions

With this algorithm, two things are accomplished:

  1. A directed acyclic graph (DAG) is created on the variable uses and definitions. The DAG specifies a data dependency among assignment statements, as well as a partial order (therefore parallelism among statements).
  2. When statement s(i) is reached, there is a list of live variable assignments. If only one assignment is live, for example, constant propagation might be used.

Read more about this topic:  Use-define Chain

Famous quotes containing the words method, building and/or chain:

    “You know, I have a method all my own. If you’ll notice, the coat came first, then the tie, then the shirt. Now, according to Hoyle, after that the pants should be next. There’s where I’m different. I go for the shoes next. First the right, then the left. After that, it’s every man for himself.”
    —Robert Riskin (1897–1955)

    “History is a child building a sand-castle by the sea, and that child is the whole majesty of man’s power in the world.”
    —Heraclitus (c. 535–475 B.C.)

    “Oft, in the stilly night, Ere Slumber’s chain has bound me, Fond Memory brings the light Of other days around me.”
    —Thomas Moore (1779–1852)