[aarch64-port-dev ] RFR: 8144993: Elide redundant memory barrier after AllocationNode

[Andrew Haley]

On 12/17/2015 03:28 PM, Hui Shi wrote:
> Could discussion limit to 8144993 in this thread. Stated in early mail, it
> looks safe in 3 cases for references from both GC thread or other java
> thread.
> 
> 8136596 enhances original optimization from noEcape to both noescape and
> argescape. As said in your new example, both allocations are noescape, so
> it's not directly related with 8136596.  How about starting a new thread
> discussing if there is possible danger in original storestore  barrier
> optimization?

I say we should not do that.  Martin's concern is real, and you have
shown no reason to suppose that removing the memory barriers will not
result in a concurrent GC seeing stale object headers.  As it stands,
unless someone can come up with something convincing, we're going to
have to restore those memory barriers.  8144993 should not be committed
until this issue is resolved.

Andrew.