And in fact; minnow@minnow:~$ gcc -mtune=native -dM -E - < /dev/null | grep 86 #define __i586 1 #define __DBL_MAX__ ((double)1.79769313486231570815e+308L) #define __i386 1 #define __i586__ 1 #define __i386__ 1 #define i386 1 The docs say; "While picking a specific cpu-type will schedule things appropriately for that particular chip, the compiler will not generate any code that does not run on the i386 without the -march=cpu-type option being used." But in fact if I understand the output of the command Ruoyao provided, tune *is* setting arch (whilst not setting tune =-) so this compiler in this specific case ends up setting arch correctly.
