Method of Building A use-def (or ud) Chain
- Set definitions in statement s(0)
- For each i in, find live definitions that have use in statement s(i)
- Make a link among definitions and uses
- Set the statement s(i), as definition statement
- Kill previous definitions
With this algorithm, two things are accomplished:
- 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).
- 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:
“No method nor discipline can supersede the necessity of being forever on the alert. What is a course of history or philosophy, or poetry, no matter how well selected, or the best society, or the most admirable routine of life, compared with the discipline of looking always at what is to be seen? Will you be a reader, a student merely, or a seer? Read your fate, see what is before you, and walk on into futurity.”
—Henry David Thoreau (1817–1862)
“And of the other things death is a new office building filled with modern furniture,
A wise thing, but which has no purpose for us.”
—John Ashbery (b. 1927)
“We are all bound to the throne of the Supreme Being by a flexible chain which restrains without enslaving us. The most wonderful aspect of the universal scheme of things is the action of free beings under divine guidance.”
—Joseph De Maistre (1753–1821)