Program Analysis

To correctly perform optimizations such as moving invariant code out of loops or reusing common subexpressions, it is necessary to have global information about the program.[This treatment follows Marvin Schaefer, A Mathematical Theory of Global Program Optimization, Prentice-Hall, 1973.]

Control flow analysis provides information about the potential control flow:

• Can control pass from one point in the program to another?

• From where can control pass to a given point?

• Where are the loops in the program?

Data flow analysis provides information about the definition and use of variables and expressions. It can also detect certain types of programmer errors.

• Where is the value of a variable assigned?

• Where is a given assignment used?

• Does an expression have the same value at a later point that it had at an earlier point?