From owner-freebsd-current  Thu Nov 23 11:44:13 2000
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Date: Thu, 23 Nov 2000 12:43:53 -0700 (MST)
From: <janb@cs.utep.edu>
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To: David Greenman <dg@root.com>
Cc: Julian Elischer <julian@elischer.org>, current@FreeBSD.ORG
Subject: Re: slight improvement in locore.s? 
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It does not impair readability. As long as that is true, I believe its
prudent to save every byte possible...

Only my 2 cents worth.


JAn
On Thu, 23 Nov 2000, David Greenman wrote:

> >locore.s includes:
> >#define ALLOCPAGES(foo) \ 
> >        movl    R(physfree), %esi ; \
> >        movl    $((foo)*PAGE_SIZE), %eax ; \
> >        addl    %esi, %eax ; \
> >        movl    %eax, R(physfree) ; \
> >        movl    %esi, %edi ; \
> >        movl    $((foo)*PAGE_SIZE),%ecx ; \
> >        xorl    %eax,%eax ; \
> >        cld ; \
> >        rep ; \
> >        stosb
> >        
> >
> >might it be a very slight optimisation to change this to:
> >#define ALLOCPAGES(foo) \ 
> >        movl    R(physfree), %esi ; \
> >        movl    $((foo)*PAGE_SIZE), %eax ; \
> >        movl    %eax, %ecx ; \
> >        addl    %esi, %eax ; \
> >        movl    %eax, R(physfree) ; \
> >        movl    %esi, %edi ; \
> >        xorl    %eax,%eax ; \
> >        cld ; \
> >        rep ; \
> >        stosb
> >        
> >??
> 
>    Improvement in what way?
>    Readability? I don't think so.
>    Performance? This macro is only used in the initial bootstrap of the
> kernel.
>    ...changing it might save a few bytes, however.
> 
> -DG
> 
> David Greenman
> Co-founder, The FreeBSD Project - http://www.freebsd.org
> President, TeraSolutions, Inc. - http://www.terasolutions.com
> Pave the road of life with opportunities.
> 
> 
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