RFR(L): 8031755: Type speculation should be used to optimize explicit null checks
Roland Westrelin
roland.westrelin at oracle.com
Mon Mar 31 07:17:13 UTC 2014
Thanks for the review, Igor.
Roland.
On Mar 28, 2014, at 7:40 PM, Igor Veresov <igor.veresov at oracle.com> wrote:
> Seems alright.
>
> igor
>
>
> On Mar 28, 2014, at 8:52 AM, Roland Westrelin <roland.westrelin at oracle.com> wrote:
>
>> I need another review for this. Anyone?
>>
>> Roland.
>>
>> On Mar 26, 2014, at 9:55 AM, Roland Westrelin <roland.westrelin at oracle.com> wrote:
>>
>>> Thanks for the review, Vladimir.
>>>
>>> Roland.
>>>
>>>
>>> On Mar 26, 2014, at 1:43 AM, Vladimir Kozlov <vladimir.kozlov at oracle.com> wrote:
>>>
>>>> It is good.
>>>>
>>>> Thanks,
>>>> Vladimir
>>>>
>>>> On 3/25/14 7:53 AM, Roland Westrelin wrote:
>>>>> Thanks for reviewing this, Vladimir!
>>>>>
>>>>>> Looks good. I see next expression several times:
>>>>>>
>>>>>> speculative ? Deoptimization::Reason_speculate_null_check : Deoptimization::Reason_null_check
>>>>>>
>>>>>> Can you put it into method Deoptimization::reason_null_check(speculative)?
>>>>>
>>>>> Here it is:
>>>>>
>>>>> http://cr.openjdk.java.net/~roland/8031755/webrev.02/
>>>>>
>>>>> I did the same for Reason_speculate_class_check & Deoptimization::Reason_class_check.
>>>>>
>>>>> Roland.
>>>>>
>>>>>>
>>>>>> Thanks,
>>>>>> Vladimir
>>>>>>
>>>>>> On 3/20/14 4:52 AM, Roland Westrelin wrote:
>>>>>>>>> I made the following change:
>>>>>>>>>
>>>>>>>>> *** 3561,3571 ****
>>>>>>>>>
>>>>>>>>>
>>>>>>>>> // Since klasses are different, we require a LCA in the Java
>>>>>>>>> // class hierarchy - which means we have to fall to at least NotNull.
>>>>>>>>> if( ptr == TopPTR || ptr == AnyNull || ptr == Constant )
>>>>>>>>> ptr = NotNull;
>>>>>>>>>
>>>>>>>>> - instance_id = InstanceBot;
>>>>>>>>>
>>>>>>>>>
>>>>>>>>> // Now we find the LCA of Java classes
>>>>>>>>> ciKlass* k = this_klass->least_common_ancestor(tinst_klass);
>>>>>>>>> return make(ptr, k, false, NULL, off, instance_id, speculative, depth);
>>>>>>>>> } // End of case InstPtr
>>>>>>>>>
>>>>>>>>> --- 3706,3715 ——
>>>>>>>>>
>>>>>>>>> because I hit a type not symmetric failure that I think it causes:
>>>>>>>>>
>>>>>>>>> === Meet Not Symmetric ===
>>>>>>>>> t = javax/management/openmbean/OpenType:AnyNull * (inline_depth=-2)
>>>>>>>>> this= javax/management/openmbean/ArrayType:TopPTR *,iid=top (inline_depth=InlineDepthTop)
>>>>>>>>> mt=(t meet this)= javax/management/openmbean/ArrayType:AnyNull * (inline_depth=-2)
>>>>>>>>> t_dual= javax/management/openmbean/OpenType:NotNull *,iid=top (inline_depth=2)
>>>>>>>>> this_dual= javax/management/openmbean/ArrayType *
>>>>>>>>> mt_dual= javax/management/openmbean/ArrayType:NotNull *,iid=top (inline_depth=2)
>>>>>>>>> mt_dual meet t_dual= javax/management/openmbean/OpenType:NotNull * (inline_depth=2)
>>>>>>>>> mt_dual meet this_dual= javax/management/openmbean/ArrayType *
>>>>>>>>
>>>>>>>> The question is why OpenType:AnyNull does not have iid=top. It is in upper type lattice.
>>>>>>>
>>>>>>> http://cr.openjdk.java.net/~roland/8031755/TestMeetInstanceId.java
>>>>>>>
>>>>>>> triggers this. But while working on reproducing it, I noticed a bug in the previous webrev:
>>>>>>>
>>>>>>> if (!speculative_maybe_null) {
>>>>>>>
>>>>>>> in TypePtr::would_improve_ptr() should have been:
>>>>>>>
>>>>>>> if (!speculative_maybe_null()) {
>>>>>>>
>>>>>>> with that fixed, the bug doesn’t reproduce. I also think we should drop the speculative type, if it is above the center line. So here is a new webrev with:
>>>>>>> instance_id = InstanceBot;
>>>>>>> back where it was.
>>>>>>>
>>>>>>> http://cr.openjdk.java.net/~roland/8031755/webrev.01/
>>>>>>>
>>>>>>> Roland.
>>>>>>>
>>>>>
>>>
>>
>
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