I wrote: > Using the OS GCC (4.9.2, native build for i586-linux-gnu); > WIthout, I get arch i586, tune generic. > With, I get - ha! - "-march=native", and no tune. This seems odd. A bit more information now, pairs of command/output. First on Debian 8, the OS provided 4.9.2 on my normal x86_64 machine. gcc -E -x c /dev/null -v COLLECT_GCC_OPTIONS='-E' '-v' '-mtune=generic' '-march=x86-64' gcc -march=native -E -x c /dev/null -v COLLECT_GCC_OPTIONS='-march=native' '-E' '-v' gcc -mtune=native -E -x c /dev/null -v COLLECT_GCC_OPTIONS='-mtune=native' '-E' '-v' '-march=x86-64' gcc -march=native -mtune=native -E -x c /dev/null -v COLLECT_GCC_OPTIONS='-march=native' '-mtune=native' '-E' '-v' Interetin', eh? tune is doing something, even though arch isn't. Going back to the version 1 Minnowboard (Atom E640), Debian 8, the OS provided GCC 4.9.2; gcc -E -x c /dev/null -v COLLECT_GCC_OPTIONS='-E' '-v' '-mtune=generic' '-march=i586' gcc -march=native -E -x c /dev/null -v COLLECT_GCC_OPTIONS='-march=native' '-E' '-v' gcc -mtune=native -E -x c /dev/null -v COLLECT_GCC_OPTIONS='-mtune=native' '-E' '-v' '-march=i586' gcc -march=native -mtune=native -E -x c /dev/null -v COLLECT_GCC_OPTIONS='-march=native' '-mtune=native' '-E' '-v' Superficially at least, -march is looking a bit messed up. However, it's more likely my expectation of what it is does is amiss =-)
