default compilation flags for AMD64

[Dimitris Lampridis <dlampridis@gmail.com>]

Hi everybody,
I was wondering if anyone can inform me of the default compilation flags for 
AMD64 when compiling and installing debian source packages. I suppose there 
is such a thing (there should be an -march=k8 or -mtune by default, no? ), on 
top of which every package possibly adds its own?

Also, if such a default behavior exists, is there a way to change it? Better 
even, leave it alone and change the flags for a specific package? I tried to 
tweak the sources but they get overwritten by dpkg-buildpackage, or worse 
cause the process to bail out, complaining about differences in the source.

Trivial purpose of all these is to compile Blender 2.41 from unstable sources 
and see if I can get better rendering times...

I've seen apt-build also, did sound good, but it seems very buggy and also I 
would like to learn more about the debian build process itself before 
automating it...

thanks,
Dimitris

PS: My gentoo alter-ego has taken control over me, shoot me before its too 
late :)