RFR(M): 8130847: Cloned object's fields observed as null after C2 escape analysis

[Vladimir Kozlov]

On 7/29/15 6:57 AM, Roland Westrelin wrote:
>> The next change puzzles me:
>>
>> -         if (!call->may_modify(tinst, phase)) {
>> +         if (call->may_modify(tinst, phase)) {
>> -           mem = call->in(TypeFunc::Memory);
>> +           assert(call->is_ArrayCopy(), "ArrayCopy is the only call node that doesn't make allocation escape");
>>
>> Why only ArrayCopy? I think it is most of calls. What set of tests you ran?
>>
>> Methods naming is confusing. membar_for_arraycopy() does not check for membar but for calls which can modify. handle_arraycopy() could be make_arraycopy_load().
>
> What about:
>
> static bool may_modify(const TypeOopPtr *t_oop, MemBarNode* mb, PhaseTransform *phase);
>
> instead of membar_for_arraycopy()
>
> So ArrayCopyNode would have:
>
> virtual bool may_modify(const TypeOopPtr *t_oop, PhaseTransform *phase);
>
> and
>
> static bool may_modify(const TypeOopPtr *t_oop, MemBarNode* mb, PhaseTransform *phase);
>
> that do the same thing except the static method also looks for a graph pattern starting from a MemBar.

Yes, it is better.

Thanks,
Vladimir

>
> Roland.
>
>>
>> Add explicit check:
>> && strcmp(_name, "unsafe_arraycopy") != 0)
>>
>> Thanks,
>> Vladimir
>>
>> On 7/28/15 7:05 AM, Roland Westrelin wrote:
>>> http://cr.openjdk.java.net/~roland/8130847/webrev.00/
>>>
>>> When an allocation which is the destination of an ArrayCopyNode is eliminated, field’s values recorded at a safepoint (to reallocate the object) do not take the ArrayCopyNode into account at all and the effect or the ArrayCopyNode is lost on a deoptimization. This fix records values from the source of the ArrayCopyNode, emitting new loads if necessary.
>>>
>>> I also use the opportunity to pin the loads generated in LoadNode::can_see_arraycopy_value() because they depend on all checks that validate the array copy and not only on the check that immediately dominates.
>>>
>>> Roland.
>>>
>