RFR: Can not dedup string inside write barrier

[Aleksey Shipilev]

On 11/06/2017 04:25 PM, Zhengyu Gu wrote:
> On 11/06/2017 10:13 AM, Aleksey Shipilev wrote:
>> On 11/06/2017 03:59 PM, Zhengyu Gu wrote:
>>> Can not perform String deduplication inside a write barrier, as it takes lock, that violates write
>>> barrier's leaf call constraint.
>>>
>>>
>>> Webrev: http://cr.openjdk.java.net/~zgu/shenandoah/strdedup_wb/webrev.00/
>>
>> Okay, but minor nits:
>>
>>   *) I think there is no need for templates, because the method is already slow-path. A simple
>> boolean arg would be enough? This will simplify backports too, because the signature change would be
>> needed everywhere, instead of blind substitution of evacuate_object.
> Yes, for write barrier, it is slow path. However, it is also used by GC, that can have some impact (?).

If we care as much, then ShenandoahStringDedup::is_enabled() check is already on critical path
there. So, do a boolean flag, and hide it *after* the ShenandoahStringDedup::is_enabled() check?

 373   if (ShenandoahStringDedup::is_enabled() && !from_write_barrier &&
 374       java_lang_String::is_instance_inlined(copy_val)) {

-Aleksey