How about them optimizations?

[Roop Nanuwa]

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.

--roop