RFR(M): 8209835: Aarch64: elide barriers on all volatile operations

[Roland Westrelin]

>> http://cr.openjdk.java.net/~roland/8209835/webrev.00/
>> 
>> This adds barrier elision support for all volatile operations that were
>> not supported so far and extends the tests to cover all of them. I ran
>> full jcstress successfully with this.
> Yes, that looks good.

Thanks for the review.

> Did you also eyeball the generated code? I know jcstress ought to find
> any bugs but it would be good to be doubly sure :-)

I didn't eyeball the code (there's a lot to check!). I extended tests to
cover all combination of atomic operations/argument types. So at least,
tests should guarantee that the right variant in the ad file is
picked. Then, of course, all variants must be correctly implemented. For
that, I checked a couple times that the right boolean flag was passed.

Roland.