RFR: Assembler write barriers should consistently check for forwarded objects

[Aleksey Shipilev]

On 07/10/2018 11:03 AM, Roman Kennke wrote:
> Am 10.07.2018 um 11:01 schrieb Aleksey Shipilev:
>> On 07/10/2018 10:59 AM, Roman Kennke wrote:
>>> Am 10.07.2018 um 10:56 schrieb Aleksey Shipilev:
>>>> http://cr.openjdk.java.net/~shade/shenandoah/sbs-forwarded-check/webrev.01/
>>>>
>>>> This fixes the bug in write_barrier_impl in x86_64: we should check either for 0, or for
>>>> HAS_FORWARDED when deciding to omit the read barrier. C1 write barrier tests HAS_FORWARDED and it
>>>> seems most efficient when coalescing is not available. So, the rest homogenizes the check shape
>>>> across architectures.
>>>>
>>>> Testing: tier3_gc_shenandoah (x86_64), build (aarch64)
>>>>
>>>> Thanks,
>>>> -Aleksey
>>>>
>>>
>>> Can you hold it back until I pushed the consolidation?
>>
>> I think it is cleaner to go the other way around: we first push this thing that fixes the barriers,
>> because it is also backportable, then we rebase and push consolidation, that is less backportable.
>> But either way, I can redo the patch during backports...
> 
> Ok, then please push that change, and I'll re-do the consolidating patch.

Pushed.

-Aleksey