RFR: 8218767: ZGC: Do not assume that r12 is a special register in C2

[Per Liden]

Thanks Roman and Erik!

/Per

On 2/20/19 12:08 PM, Roman Kennke wrote:
> Looks ok to me.
> 
> Thanks,
> Roman
> 
>> Updated version rebased on top of JDK-8217909 (which Roman will push
>> soonish).
>>
>> http://cr.openjdk.java.net/~pliden/8218767/webrev.1
>>
>> cheers,
>> Per
>>
>> On 2/19/19 2:40 PM, Per Liden wrote:
>>> The C2 load barrier code for ZGC assumes that r12 is not used as a
>>> general purpose register. However, JDK-8217909 might change that, so
>>> ZGC should not be making this assumption.
>>>
>>> Bug: https://bugs.openjdk.java.net/browse/JDK-8218767
>>> Webrev: http://cr.openjdk.java.net/~pliden/8218767/webrev.0
>>>
>>> /Per
>