Program Analysis

In order for a compiler to perform certain 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 there loops in the program?

Data flow analysis provides information about the definition and use of variables and expressions. It can also provide valuable detection of 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?

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