How about them optimizations?

[Kris Kennaway]

On Tue, Feb 10, 2004 at 12:14:46PM -0800, Roop Nanuwa wrote:
> Part of my current /etc/make.conf on my 5.2-CURRENT box looks like:
> 
> CPUTYPE= athlon-xp
> CFLAGS= -O2 -pipe -fomit-frame-pointer -mmmx -msse -m3dnow -mfpmath=sse
> COPTFLAGS= -O -pipe
> 
> Now what I'm wondering is if those extras like mmmx msse actually do 
> anything. The
> only reason they're in there is because I saw them on a website about 
> what people
> use to optimize gentoo. I had nothing better to do so I recompiled the 
> world with
> them. I didn't really notice anything good or bad happening after that. 
> I did have
> to mess around with a couple of makefiles to get around the 
> strict-aliasing problem
> that O2 introduces. Besides that, though, are there any advantages or 
> disadvantages
> to compiling with those optimizations and switches?
> 
> Does -mfpmath=sse actually do anything relevent for the FreeBSD world? I 
> know
> what the GCC manual says about it but I'd rather hear some real world info.
> 
> An enquiring mind wants to know.

That's superfluous, because gcc already uses all available opcodes
when you tell it to optimize for your CPU type with CPUTYPE=athlon-xp.
Using -O2 is recommended against, though - see the sample make.conf
file.

Kris
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