RFR (M): 8187977: Generalize Atomic::xchg to use templates

[Kim Barrett]

> On Sep 29, 2017, at 6:45 AM, Erik Österlund <erik.osterlund at oracle.com> wrote:
> 
> Hi Kim,
> 
> Thanks for looking at this.
> 
> Incremental webrev:
> http://cr.openjdk.java.net/~eosterlund/8187977/webrev.00_01/
> 
> Full webrev:
> http://cr.openjdk.java.net/~eosterlund/8187977/webrev.01/

Looks good.

I’ll get back to you if I come up with any ideas for improving the canonicalization of store_value and dest.