Draw a data flow graph for the code fragment of Example 5.5. Assign an order of execution to the nodes in the graph so that no more than four registers are required. Explain how you arrived at your solution using the structure of the data flow graph.

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Example 5.5 Data-Dependent Paths in if Statements Here is a pair of nested if statements: if (ab) { /* test 1 */ if (c) test 2 */ (x-rs+t; /* assignment 1 */ } elsey r+s: /* assignment 2 */ } z=r+s+u; /* assignment 3 */ } else { if (c) / test 3 */ ly r t / assignment 4 */ } The conditional tests and assignments are labeled within each if statement to make it easier to identify paths. What execution paths may be exercised? One way to