13 Control Flow Graph
A control flow graph (CFG) is a data structure built on top of the
intermediate code representation (the RTL or tree instruction
stream) abstracting the control flow behavior of a function that is
being compiled. The CFG is a directed graph where the vertices
represent basic blocks and edges represent possible transfer of
control flow from one basic block to another. The data structures
used to represent the control flow graph are defined in
basic-block.h.