RFR: 8256011: Shenandoah: Don't resurrect finalizably reachable objects [v5]

[Zhengyu Gu]

On Tue, 10 Nov 2020 13:28:13 GMT, Roman Kennke <rkennke at openjdk.org> wrote:

>> In the weak-LRB we currently return referents when it is 'marked', that is when it's either reachable strongly or through a finalizable object. This means a finalizable object can be resurrected by Reference.get(), which is wrong. Only truly strongly reachable objects should be returned by Reference.get() during weak-reference-processing. 
>> 
>> I had to reconsider the way we call into runtime-LRBs from generated code for these reasons:
>>  - We need to distinguish phantom, weak and strong reference strength, and native vs in-heap access. Those are two orthogonal dimensions
>>  - We can have strong and phantom native referents, and strong and weak in-heap referents
>>  - Native referents are never compressed
>> 
>> Note that this depends on PR#1140.
>> 
>> Testing:
>>  - [x] hotspot_gc_shenandoah
>>  - [x] tier1 +UseShenandoahGC +ShenandoahVerify
>>  - [ ] tier2 +UseShenandoahGC +ShenandoahVerify
>
> Roman Kennke has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Aarch64 parts

Changes requested by zgu (Reviewer).

src/hotspot/cpu/x86/gc/shenandoah/shenandoahBarrierSetAssembler_x86.cpp line 958:

> 956:   }
> 957: #else
> 958:   __ load_parameter(0, rax);

Dose not seem that x86_32 made adjustment as x86_64. Dose it even build on x86_32?

-------------

PR: https://git.openjdk.java.net/jdk/pull/1109