On 21/01/2012, Erik Leunissen wrote: > L.S. > > I'd like to generate code that runs on a selection of common 64-bit > cpu's, both Intel and AMD[*]. > > [*] Aside: I'm not yet entirely sure yet about the final selection > of architectures, but in any case I would like to support core2, atom, > athlon64 (not yet sure about opteron and AMD multicore cpu's). > > To that end, I've been looking in the list of "-march" options to gcc > for a specific option that indicates such a common set of architectures > (much like "-march=i686" for 32-bit architectures). > > I remain confused about how to do this for 64-bit cpu's. I found several > options indicating specific cpu's that I'd like to run my code on. > However, I guess that I'm clueless about "backward compatibility" of > (closely) related 64-bit cpu types (like i386 code being supported by > i686 with 32-bit cpu's). Also, I'm unsure about the differences between > AMD and Intel in this regard. > > - Do options indicating such a generic 64-bit cpu exist?, or Why do you think you need to use any -march option? If do don't use one you'll get code that runs on any x86_64 machine. > - Can I specifiy multiple -march options in one compile command?, or No. > - Do I need to compile separately for each 64-bit architecture?, or > - ... ? > > I'd appreciate very much any directions about how to proceed. Just compile without any -march, unless you're sure your code will always run on chips that support more specific features. Each -march option lists the features it enables, so you should be able to work out what options will work for all the machines you want to use. e.g. don't use -march=core2 if you want to support chips without SSSE3. You can always use -mtune=generic to generate code that is tuned for common chips, but still runs on older ones.
