The Flow Analysis and Transformation

Machine SUIF 6] is an extension of the SUIF compiler framework that facilitates experiments with machine-speciic optimizations. Just as base SUIF 7] is built on a rich collection of libraries for machine-independent analysis and transformation, machine SUIF has a growing set of libraries for working at the machine level. This note is about the libraries for ow analysis to support ow-directed transformation. The control ow graph (CFG) library 8] makes it easy for compiler passes to manipulate programs using a graph representation extracted from their control ow. The data ow analysis (DFA) library 4] develops data ow information about programs represented as CFG's. We summarize the goals and capabilities of these two libraries, and we mention how they're used in register allocation and code rearrangement. The machine SUIF library for instruction scheduling, which makes use of both ow libraries, is described in a companion paper 3]. 1 The CFG Library 1.1 Design Goals Analysis. The control ow graph is an important data structure for many compiler operations. The library provides an abstract data type for the ow graph, including methods to traverse and examine its nodes. Such methods include iterating through the nodes in various useful orders, traversing links to and from a node, and iterating over the instructions that make up a node. There are also methods for some analysis algorithms that recur in program optimization, such as computing dominance relations and nding natural loops.