Editing Control-flow graph (section)

==Special edges==

A ''back edge'' is an edge that points to a block that has already been met during a depth-first ([[depth-first search|DFS]]) traversal of the graph. Back edges are typical of loops.

A ''critical edge'' is an edge which is neither the only edge leaving its source block, nor the only edge entering its destination block. These edges must be ''split'': a new block must be created in the middle of the edge, in order to insert computations on the edge without affecting any other edges.

An ''abnormal edge'' is an edge whose destination is unknown. [[Exception handling]] constructs can produce them. These edges tend to inhibit optimization.

An ''impossible edge'' (also known as a ''fake edge'') is an edge which has been added to the graph solely to preserve the property that the exit block postdominates all blocks. It cannot ever be traversed.