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The format of a prefetch instruction resembles that of a normal load instruction, except that there is no need to specify a destination register. Therefore addressing modes that are appropriate for normal loads are also appropriate for prefetches. The addressing mode used in these experiments was ``base-plus-offset'', as shown in Figure . This addressing mode is attractive because prefetch address can typically be generated by using the same base register as the load or store being prefetched and simply adjusting the constant offset to reflect the software pipelining distance. An example of this is shown in Figure , where the prefetch instruction is fetching data five iterations ahead of the load instruction, and both instructions use the same base register (r7). This is important in order to avoid spilling registers once prefetches are inserted. Addressing modes which cannot take advantage of such register reuse should be avoided.

Sat Jun 25 15:13:04 PDT 1994