Performance on PPC8xx using string and multiple load instructions?

Hello,

Does anyone know how using the -mstring and -mmultiple GCC
code optimization switches affect performance on the PPC8xx ? The book I have on PPC assembly says the use of the string and load-multiple instrutions may be signifigantly slower than the multiple instruction equivalent on some processors. It does not tell me which processors or why. I think it might be due to ther fact that multiple instructions can be paired in multi instruction pipelined chips. Since the 8xx has only a sigle pipeline I was wondering if this was the case.

In the kernel source they use the -mmultiple and -mstring
switches in the architecture dependant code. This may be done to reduce codeIf these are
instructions signifigantly slower on some processors is this a good idea to have them as default optimizations for all processors?

If anybody ever benchmarked code with these instructions
on an 8xx processor or other processor I would like to see the results.

Thanks in advance

Conn

--

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If you live at home long enough, your parents will move out.
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Conn Clark
Engineering Stooge [email protected]
Electronic Systems Technology Inc. www.esteem.com

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