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Subject: Re: curiosity killed the cat... hi/lo bit C verses Assembly

Author: Walter Faxon

Date: 22:02:14 07/17/03

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On July 17, 2003 at 19:27:28, Gerd Isenberg wrote:

...
>the only reason nowadays to write assembler stuff is IMHO using MMX, SSE2 and
>special processor instructions, the compiler don't supply, like bsf and cmov for
>MSC.
...


Hi, Gerd.

Viz. MS Visual C 6 and generation of the "cmov" (conditional move)
instruction, Matt Taylor informs me (from a couple of emails):

-----
Pentium Pro, Pentium 2, and Pentium 3 are all the same design, but the
latter processors have been tweaked significantly.  Targeting one
should effectively target them all in this case.

Compiler option is /arch:SSE|SSE2

The bsf/bsr instructions are available as of VC 8.
-----

If instead you're using the IDE this would be:

    Project Settings dialog
        C/C++ tab
        Category: Code Generation
        Processor: Pentium Pro

I guess this all means that one can reasonably hope that selecting for the
Pentium Pro should allow generation of cmov, though I would prefer an experiment
to verify this.  You might try getting an assembly output for the code I posted
in message:  http://www.talkchess.com/forums/1/message.html?306363

If that works I'll post it as a macro, additionally providing more
functionality.  Tell me whether you want lsb=0 or lsb=63.

-- Walter



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