From mboxrd@z Thu Jan 1 00:00:00 1970 Message-ID: <3CDAB099.11A0DC74@esteem.com> Date: Thu, 09 May 2002 10:23:37 -0700 From: Conn Clark MIME-Version: 1.0 To: linuxppc-embedded@lists.linuxppc.org Subject: Performance on PPC8xx using string and multiple load instructions? Content-Type: text/plain; charset=us-ascii Sender: owner-linuxppc-embedded@lists.linuxppc.org List-Id: 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 -- ***************************************************************** If you live at home long enough, your parents will move out. ***************************************************************** Conn Clark Engineering Stooge clark@esteem.com Electronic Systems Technology Inc. www.esteem.com ** Sent via the linuxppc-embedded mail list. See http://lists.linuxppc.org/