Live ness shows that a variable is potentially of future use in a program. The very busy expressions problem if an expression's value is certainly of future use.
(a) Is this a forward or backward problem?
(b) What is the best solution?
(c) Describe the effects of a node on an expression.
(d) How are solutions summarized at common control flow points?
(e) How would you determine live ness for a set of expressions?