[Patch ping] was: Option to compile for both AMD64 and EM64T?

[Kelley Cook]

Justin Palmer wrote:
> Hi,
> 
> Since the differences between AMD64 and EM64T are minor, will GCC have an option to compile applications for both?
> 
> Linux-Kernel Archive reference:
> http://www.ussg.iu.edu/hypermail/linux/kernel/0402.3/0276.html
> 
> Currently, the -mtune, -march, and -mcpu values must specify one of: nocona, k8, opteron, athlon64, or athlon-fx.  My software group has been using i686 to build one executable for both Intel and AMD 32-bit processors and would like to build one executable for their 64-bit processors.
> 
> Also, do the docs need updated for -m64 or is that option really for AMD64 only?

With the experimental GCC 3.5, -march=x86-64 does what you want.  You 
probably could backport the patch to GCC 3.4 without much problem.

And the reminds of a patch that I submitted a while ago which resets the 
default x86 complier to the generic version for same reason you mentioned.

Could someone review 
http://gcc.gnu.org/ml/gcc-patches/2004-05/msg00352.html?