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Subject: Re: BitScan with reset - not so impressive with 3DNow!

Author: Russell Reagan

Date: 12:15:27 12/03/02

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On December 03, 2002 at 10:09:31, Gerd Isenberg wrote:

>Let's see how fast Hammer's bsf reg64,reg64 will be.
>If it sucks like Athlon, there are a lot of good alternatives.
>I guess that with 64-bit arithmetic, to do a fast single bit isolation the trick
>with 64int to 32bit float conversion is promising.

I remember Eugene Nalimov giving a C routine for Crafty's FirstOne() that would
run in ~12 cycles on the Itanium, after optimizations. bsf might not be needed
at all.

Which is faster on for finding the lsb of a 32-bit value on 32-bit hardware? bsf
or a C-routine? If one is faster than the other on 32-bit hardware for 32-bit
values, would the same be faster for a 64-bit value on 64-bit hardware?



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