We reexamine the limits of parallelism available in programs, using run-time reconstruction of program data-flow graphs. While limits of parallelism have been examined in the context of superscalar and VLIW machines, we also wish to study the causes of observed parallelism by examining the structure of the reconstructed data-flow graph. One aspect of structure analysis that we focus on is the isolation of instructions involved only in address calculations. We examine how address calculations present in RISC instruction streams generated by optimizing compilers affect the shape of the data-flow graph and often significantly reduce available parallelism.
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