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SubjectRe: Patch to remove undefined C code
At 01:21 PM 10/16/00, Jeff Garzik wrote:
>Bernd Schmidt wrote:
> > diff -x log.build -x .* -dru linux-2.4/drivers/net/tulip/tulip_core.c
> linux-2.4-fixed/drivers/net/tulip/tulip_core.c
> > --- linux-2.4/drivers/net/tulip/tulip_core.c Mon Oct 16 13:51:23 2000
> > +++ linux-2.4-fixed/drivers/net/tulip/tulip_core.c Mon Oct 16
> 15:40:12 2000
>[...]
> > @@ -944,9 +946,9 @@
> >
> > /* Fill the final entry with our physical address. */
> > eaddrs = (u16 *)dev->dev_addr;
> > - *setup_frm++ = *setup_frm++ = eaddrs[0];
> > - *setup_frm++ = *setup_frm++ = eaddrs[1];
> > - *setup_frm++ = *setup_frm++ = eaddrs[2];
> > + *setup_frm++ = eaddrs[0]; *setup_frm++ = eaddrs[0];
> > + *setup_frm++ = eaddrs[1]; *setup_frm++ = eaddrs[1];
> > + *setup_frm++ = eaddrs[2]; *setup_frm++ = eaddrs[2];
> >
> > spin_lock_irqsave(&tp->lock, flags);
> >

Looking at the above code, I noticed that there are a lot of ++
operations. I rewrote the code as:

setup_from[0] = setup_from[1] = eaddrs[0];
setup_from[2] = setup_from[3] = eaddrs[1];
setup_from[4] = setup_from[5] = eaddrs[2];
setup_from += 6;

I compiled using "gcc -S -Wall -O2 -fomit-frame-pointer -m486" to generate
the assembler code. The old code is 17 instructions long and the new code
is 11 instructions. As well as being shorter, simple timing test indicate
that the new code is significantly quicker.

David

--------------------------------------------------------
David Relson Osage Software Systems, Inc.
relson@osagesoftware.com 514 W. Keech Ave.
www.osagesoftware.com Ann Arbor, MI 48103
voice: 734.821.8800 fax: 734.821.8800

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