/*  C O N T R O L   F L O W
 *
 *  S U C C E S S O R  /  P R E D E C E S S O R   R E L A T I O N S
 */

extern control_flow();		/* (bblock_p head)
				 * Compute for every basic block
				 * its successors and predecessors
				 * in the control flow graph.
				 */