These macros are needed to make sure the compiler does not optimize away
atomic constructs such as "while (!READ_ONCE(foo))" loops that do not
modify foo within the loop
Also move the barrier() define where it belongs while we are here, it is
needed for READ_ONCE/WRITE_ONCE and including ihk/cpu.h here causes
include loops
Change-Id: Ia533a849ed674719ccbc0495be47d22a3c47b8f8
Had to remove from original compiler-gcc:
- things that deal with types, e.g. READ_ONCE macro and friends;
- #define barrier(). This one would be better there at some point.
