Unrestricted Code Motion: A Program Representation and Transformation Algorithms Based on Future Values

Abstract. We introduce the concept of future values. Using future values it is possible to represent programs in a new control-flow form such that on any control flow path the data-flow aspect of the computation is either traditional (i.e., definition of a value precedes its consumers), or reversed (i.e., consumers of a value precede its definition). The representation hence allows unrestricted code motion since ordering of instructions are not prohibited by the data dependencies. We present a new program representation called Recursive Future Predicated Form (RFPF) which implements the concept. RFPF subsumes general if-conversion and permits unrestricted code motion to the extent that the whole procedure can be reduced to a single block. We develop algorithms which enable instruction movement in acyclic as well as cyclic regions and give examples of various optimizations in RFPF form.

• Type: Journal
• Year: 2010
• Where: CC
• Authors: Shuhan Ding, Soner Önder
• Keywords: CC 2010, Control Flow Path, Future Values, System Software, Unrestricted Code Motion