gcc:
-Os, -O2 -O3. -O2 , . , , -Os .
-march = native ( , ) . . gcc uses with native, :
C, test.c,
$ touch test.c
$ gcc -march=native -fverbose-asm -S test.c
$ cat test.s
goto Gentoo.
gcc. : i7, gcc 4.5 Atom, -march -mtune .
, (-, Gentoo, -march = native ) http://gcc.gnu.org/onlinedocs/gcc/i386-and-x86_002d64-Options.html
4.4 4.5, -flto -fwhole-program. , . , , GCC http://gcc.gnu.org/onlinedocs/gcc/Optimize-Options.html