Tech Report CS-88-16

An Efficient Method of Computing Static Single Assignment Form

Ron Cytron, Jeanne Ferrante, Barry K. Rosen, Mark N. Wegman, F. Kenneth Zadeck

October 1988


In optimizing compilers, data structure choices directly influence the power and efficiency of practical program optimization. A poor choice of data structure can inhibit optimization or slow compilation to the point where advanced optimization features become undesirable. Recently, static single assignment form and the control dependence graph have been proposed to represent data flow and control flow properties of programs. Each of these previously unrelated techniques lends efficiency and power to a useful class of program optimizations. Although both of these structures are attractive, the difficulty of their construction and their potential size have discouraged their use. We present a new algorithm that efficiently computes these data structures for arbitrary control flow graph We also give analytical and experimental evidence that they are usually {\em linear} in the size of the original program. This paper thus presents strong evidence that these structures can be of {\em practical} use in optimization.

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