RFR: Cherry-pick: 8213199: GC abstraction for Assembler::needs_explicit_null_check() plus Shenandoah parts

[Aleksey Shipilev]

On 11/12/2018 10:56 PM, Roman Kennke wrote:
>>> In preparation for next upstream merge (reduce conflicts and headaches
>>> sorting it out), this cherry picks "8213199: GC abstraction for
>>> Assembler::needs_explicit_null_check()" plus the corresponding Zero
>>> fixes by Aleksey (JDK-8213711) and adds the Shenandoah parts.
>>>
>>> http://cr.openjdk.java.net/~rkennke/JDK-8213199-shenandoah/webrev.00/
>>
>> OK.
>>
>> I think there are trailing newline differences in:
>>   src/hotspot/cpu/arm/macroAssembler_arm.hpp
>>   src/hotspot/os_cpu/aix_ppc/os_aix_ppc.cpp
>>   src/hotspot/os_cpu/linux_arm/os_linux_arm.cpp
> 
> I did a straight hg qimport and those files did not conflict or
> anything, how would that have happened? The orginal patch includes the
> same trailing newline removals:
> 
> http://hg.openjdk.java.net/jdk/jdk/rev/4ad404da0088

Looks to me, these are legit whitespace changes that are coming from upstream. So, we are fine with
cherry-picking the patch.

-Aleksey