Computers as Components, 2nd Edition

220 CHAPTER 5 Program Design and Analysis

C code

CDFG

F

T

while (a < b) {

a5 proc1(a,b);

b5 proc2(a,b);

}

a < b

a 5 proc1(a,b);

b 5 proc2(a,b);

FIGURE 5.7

CDFG for a while loop.

We can define a state variable that represents a program counter in a CPU. (When

studying a drawing of a CDFG,a finger works well for keeping track of the program

counter state.) As we execute the program, we either execute the data flow node

or compute the decision in the decision node and follow the appropriate edge,

depending on the type of node the program counter points on. Even though the

data flow nodes may specify only a partial ordering on the data flow computations,

the CDFG is