Single byte Atomic::cmpxchg implementation

[Andrew Haley]

On 08/09/14 03:11, David Holmes wrote:
> Note there is currently no ARM code in the OpenJDK itself. Of course the 
> Aarch64 project will hopefully be changing that soon, but I would not 
> think they need the logic you describe below.

>From the AArch64 project's point of view, all we need is for the
single byte Atomic::cmpxchg implementation to be move into os_cpu/
and we can do the rest.

The question in my mind is the extent to which we need to maintain
compatibility with old C++ compilers.  Modern ones have all the
primitives we need as builtins, and will often generate better code
than with inline assembler.

Andrew.