This patch adds configure options --with-arch-32 --with-arch-64
--with-cpu-32 --with-cpu-64 --with-tune-32 --with-tune-64, similar to
--with-arch etc. but controlling the defaults separately for 32-bit
and 64-bit code generation. The option names follow the preferences
expressed at
<http://gcc.gnu.org/ml/gcc-patches/2007-06/msg00257.html>; that thread
also provides further rationale for when this sort of configuration is
of use (if you wish to have a toolchain with a minimum 32-bit CPU that
isn't 64-bit capable, but also with 64-bit support, for example).
This patch only provides an implementation for x86/x86_64;
implementations for each additional target would be essentially
independent.