Abstract

cfl Springer-Verlag Abstract. The static single-assignment (SSA) form of a program provides data flow information in a form which makes some compiler optimizations easy to perform. In this paper we present a new, simple method for converting to SSA form, which produces correct solutions for nonreducible control-flow graphs, and produces minimal solutions for reducible ones. Our timing results show that, despite its simplicity, our algorithm is competitive with more established techniques. 1 Introduction The static single-assignment (SSA) form is a program representation in which variables are split into "instances. " Every new assignment to a variable-- or more generally, every new definition of a variable-- results in a new instance. The variable instances are numbered so that each use of a variable may be easily linked back to a single definition point. Figure 1 gives a example of SSA form for some straight-line code. As its name suggests, SSA only reflects static properties; in the example, V1's value is a dynamic property, but the static property that all instances labelled V1 refer to the same value will still hold.

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