ref: 9ee2b3a6867504b2ad37c13f2ea9fe25a9165b64
dir: /sys/src/cmd/gefs/atomic.h/
long agetl(long*); vlong agetv(vlong*); void* agetp(void**); long asetl(long*, long); vlong asetv(vlong*, vlong); void* asetp(void**, void*); long aincl(long*, long); vlong aincv(vlong*, vlong); int acasl(long*, long, long); int acasv(vlong*, vlong, vlong); int acasp(void**, void*, void*); void coherence(void);