> As far as X86 is concerned i386/i486/i586 are very different from later > generation > processors. I am wondering whether another host and target architecture > could be > created called i686 that makes use of something like MMX or other > registers in Intel > Pentium II/III/4 and AMD Athlon to negate the lack of general purpose > registers.
I don't see how. MMX/SSE is suitable for SIMD processing of media data and to some extent for floating point, but is largely unusable for ad-hoc integer computation, especially anything that involves address calculations. > The fact that QEMU works and can be optimised on x86_64 is the only > saving grace > for the architecture, that is still suffering from a lack of registers > compared to any > other architecture. The lack of registers isn't ideal, but it's not a big deal, and in the grand scheme of things x86_64 has a lot going for it. The most important of which are that (from the software side) all the hard-won knowledge of how to compile good code for x86 carries across more or less directly to x86_64, and (from the hardware side) hardware people already know how to make fast, cheap x86s, so it's easy to move to making fast, cheap x86_64s. The problems of the gcc backend to qemu have already been discussed extensively on this list. Stealing 3+ registers from gcc on x86 really is asking for trouble, and I believe it is generally understood that the best long term solution is to move to a self-contained back end that does not use gcc for dynamic code generation. J _______________________________________________ Qemu-devel mailing list Qemu-devel@nongnu.org http://lists.nongnu.org/mailman/listinfo/qemu-devel
