Re: [GD-Windows] VC8.0 and CMOV

[Alen L. <ale...@cr...>]

Well, yes I tried that. Creating an inline function with _asm to
compare two numbers does work, but it seems to mess up with the
compiler's optimizations of the rest of the function, because I can't
input and output floats or ALU flags in any other way than through
memory.

Regarding the architecture, I'm optimizing this with /arch:SSE which,
according to MSDN, implies using CMOV as well, but the complier never
uses that instruction by itself.

(BTw, sorry if this seems a bit off-topic, but google doesn't help,
which seems like people usually don't really care. I hoped someone in
the gamedev would already have experienced this.)

Thanks,
Alen


Andrew wrote:
> Does using "__asm" help?  You could hand-code the instructions, then.
> confer: 
> <http://msdn2.microsoft.com/EN-US/library/45yd4tzz(VS.80).aspx>,
> which is the VC8.0 specific page about using __asm anywhere a
> statement could appear.

> It could be that the scheduler doesn't know that you are guaranteeing
> that the program will be run on a Pentium Pro or better, system.
> (Pentium Pro is when that instruction was added.)  Of course, now that
> I go to look for a reference to this on the microsoft web site, this
> may not be a concern.  I'm showing my age.  

> --andy

> On Nov 23, 2007 4:45 AM, Alen Ladavac <ale...@cr...> wrote:
>> Hi all,
>>
>> Is there any way to make MSVC8.0 to generate CMOV instructions? I have
>> some performance-critical loops, with a lot of small ifs, where it
>> generates branches, and I'd like it to put cmov/fcmov there instead.
>> Allegedly, it is able to do so, but /O2 doesn't seem to help. I can't
>> even find any intrinsic to do that. Any ideas appreciated.
>>
>> Thanks,
>> Alen
>>
>>
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-- 
Alen