I've made so many changes I don't dare continue until I check the current stuff in. /test/testatomic.c performs absolutely basic tests to show that the function work as expected. Need a second test to do more detailed tests. /include/SDL_atomic.h provides declarations for all included functions. /src/atomic/linux/SDL_atomic.c provided all the functions. On a generic built the 64 bit functions work, but they are emulated. On a build for -march=pentium and above the 64 bit functions use native instructions /src/atomic/dummy/SDL_atomic.c emulates all the operations using SDL_mutex.h. /src/atomic/win32/SDL_atomic.c is a copy of dummy /src/atomic/macosx/SDL_atomic.s is a copy of dummy These versions of SDL_atomic.c provide a frame work for building the library with a mixture of native and emulated functions. This allows the whole library to be provided on all platforms. (I hope.) I hope this fits with the SDL philosophy of either providing a common subset or emulating when the platform is missing a feature. I have not added dummy, macosx, or win32 to the build. They are there as place holders for future work. I have modified congifure.in to compile sources in /src/atomic/linux. (The SDL configure.in file is an amazing piece of work and I hope I didn't mess it up. :-)

/*
    headers for MMX assembler version of SDL_MixAudio
    Copyright 2002 Stephane Marchesin (stephane.marchesin@wanadoo.fr)
    This code is licensed under the LGPL (see COPYING for details)

    Assumes buffer size in bytes is a multiple of 16
    Assumes SDL_MIX_MAXVOLUME = 128
*/
#include "SDL_config.h"

#if defined(__GNUC__) && defined(__i386__) && defined(SDL_ASSEMBLY_ROUTINES)
void SDL_MixAudio_MMX_S16(char *, char *, unsigned int, int);
void SDL_MixAudio_MMX_S8(char *, char *, unsigned int, int);
#endif
/* vi: set ts=4 sw=4 expandtab: */