Re: .../asm-i386/bitops.h performance improvements

[Gene Heskett <gene.heskett@verizon.net>]

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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-- 
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