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Date: Wed, 15 Jun 2005 08:18:24 -0400
From: Gene Heskett <gene.heskett@verizon.net>
Subject: Re: .../asm-i386/bitops.h  performance improvements
In-reply-to: <000b01c57187$ade6b9b0$2800000a@pc365dualp2>
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Cc: cutaway@bellsouth.net
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On Wednesday 15 June 2005 04:53, cutaway@bellsouth.net wrote:
>In find_first_bit() there exists this the sequence:
>
>shll $3,%%edi
>addl %%edi,%%eax
>
>LEA knows how to multiply by small powers of 2 and add all in one
> shot very efficiently:
>
>leal (%%eax,%%edi,8),%%eax
>
>
>In find_first_zero_bit() the sequence:
>
>shll $3,%%edi
>addl %%edi,%%edx
>
>could similarly become:
>
>leal (%%edx,%%edi,8),%%edx
>
To what cpu families does this apply?  eg, this may be true for intel, 
but what about amd, via etc?
>
>
>-
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-- 
Cheers, Gene
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