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

[Gene Heskett]

On Wednesday 15 June 2005 04:53, cutaway@xxxxxxxxxxxxx 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?
>
>
>-
>To unsubscribe from this list: send the line "unsubscribe
> linux-kernel" in the body of a message to majordomo@xxxxxxxxxxxxxxx
>More majordomo info at  http://vger.kernel.org/majordomo-info.html
>Please read the FAQ at  http://www.tux.org/lkml/

-- 
Cheers, Gene
"There are four boxes to be used in defense of liberty:
 soap, ballot, jury, and ammo. Please use in that order."
-Ed Howdershelt (Author)
99.35% setiathome rank, not too shabby for a WV hillbilly
Yahoo.com and AOL/TW attorneys please note, additions to the above
message by Gene Heskett are:
Copyright 2005 by Maurice Eugene Heskett, all rights reserved.
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/