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Subject: Re: definition of clones: Danchess an Crafty (another note)

Author: Robert Hyatt

Date: 17:58:28 02/17/04

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On February 17, 2004 at 17:38:13, Dan Honeycutt wrote:

>I realize I'm adding where you are subtracting due to different numbering.  What
>I'm saying is that 3/4 of the time I still have to make "an adjustment" to the
>value bsf/bsr gives.  Do you not have to make an adjustment 4/4 of the time, or
>do you have to make 2 adjustments?
>
>Dan H.


I do it at the end, one time.  IE for the Opteron, it looks like this:

movq    %rax,63
bsfq    %rbx, %rcx
subq    %rcx, %rax    ; done, result in rax (64 bit reg).

for X86, I do it in three steps:

first check one half, then add 32,
second check other half
subtract from 63

I can post the x86 if you want...



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