[arch-dev-public] x86_64: improving default CFLAGS

[Andreas Radke]

http://bbs.archlinux.org/viewtopic.php?id=27139

after some discussions in this thread we want to change our default
compiler flags. we want to make use of the SSE3 extensions most x86_64
cpus have.

to not break backward compatibility for those few early cpus that lack
SSE3 extensions we want to do it with -mtune. this is how we want to
set it for the future:

CFLAGS="-march=x86-64 -mtune=nocona -O2 -pipe"
CXXFLAGS="-march=x86-64 -mtune=nocona -O2 -pipe"

some testing is still required. i would like to put a modified version
of pacman to testing right after it has moved to current. when
everything is ok we would ask the pacman devs to change it to the
default makepkg.conf.

please discuss.

Andy

(for i686 are also some speedups possible but that's not my task)