RFR: Make C1 write-barrier use a stub instead of dedicated instruction

[Zhengyu Gu]

shenandoahBarrierSetC1.hpp L#116

G1PreBarrierStub -> ShenandoahWriteBarrierStub

-Zhengyu


On 07/03/2018 06:56 AM, Aleksey Shipilev wrote:
> On 07/03/2018 12:50 PM, Roman Kennke wrote:
>> We currently use a dedicated C1 LIR instruction to implement the
>> Shenandoah write barrier. This is not easily supported by the current
>> BarrierSetC1 interface. What works better is to use CodeStub (like all
>> other GC's barriers), so let's turn Shenandoah's write barrier (back) to
>> using CodeStubs. This removes a whole lot of upstream changes and
>> confines Shenandoah barrier stuff to gc/shenandoah.
>>
>> http://cr.openjdk.java.net/~rkennke/c1-shenandoah-codestubs/webrev.01/
> 
> *) Comment is wrong in ShenandoahBarrierSetC1::write_barrier_impl:
> 
>   224   // Read the marking-in-progress flag.
> 
> Otherwise looks good!
> 
> -Aleksey
>