If the limit flow graph is a single node then the graph is reducible.

Control Tree

The result of applying a sequence of such transformations produces a control tree. It is defined as follows:

• The root is sn abstract graph representing the original flowgraph
• The leaves are individual basic blocks
• The internal nodes are abstract nodes representing regions of the flowgraph
• The edges of the tree represent the relationship between each abstract node and the regions that are its descendants