Fig. 1

This figure illustrates how the program graph is constructed from the CFG on a toy example with three basic blocks. Figure (a) demonstrates, that for each basic block independently we construct a computational tree. On fig (b) we can see, that each tree is completed with two nodes - a source and a sink, this way turning it into a directed acyclic graph (DAG). On fig (c) we demonstrate how all DAGs are connected following the same topology as CFG had initially