Kontrollflytgraf

Kontrollflytgraf is a representation of the possible execution paths of a computer program. In a kontrollflytgraf, nodes correspond to basic blocks—straight-line chunks of code with one entry and one exit—and directed edges reflect how control may move from one block to another.

Constructing a kontrollflytgraf typically begins during compilation or static code analysis. The program is divided into basic blocks at branches and jumps, including conditional branches and exception handling. An edge is added from block A to block B if control can transfer from A to B, with a fall-through edge for sequential execution.

It is used to support program analysis and optimizations. Analyses such as liveness, reaching definitions, and data-flow analysis operate on CFGs to determine properties of variables and expressions. CFGs are also instrumental in optimizations like dead-code elimination, constant propagation, and register allocation, and underlie many compiler passes.

CFGs can be static, deriving from source or intermediate representations, or dynamic, reflecting runtime behaviour. Real programs with exceptions, abrupt exits, or concurrency may yield irreducible graphs or non-deterministic edges, complicating analyses. Reducible CFGs are easier to analyse, and many tools approximate dynamic control flow.

Applications and tools: compilers such as LLVM and GCC construct CFGs as part of optimization pipelines, and visualization tools can render CFGs using graph description formats.